EP4621320A1

EP4621320A1 - Refrigeration system

Info

Publication number: EP4621320A1
Application number: EP23891626.6A
Authority: EP
Inventors: Toru Mori; Kazuhiko Mihara; Asuka YANO
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2022-11-17
Filing date: 2023-11-15
Publication date: 2025-09-24
Also published as: WO2024106479A1

Abstract

The present disclosure provides a refrigeration system capable of efficiently executing a defrosting operation while preventing a decrease in heating capacity. The refrigeration system according to the present disclosure includes: a refrigeration cycle circuit that connects an outdoor unit including a compressor and an outdoor heat exchanger, an indoor unit including an indoor heat exchanger, and a refrigeration-facility unit including a refrigeration-facility heat exchanger; and a control unit, the refrigeration cycle circuit includes a switching mechanism that switches a flow path of a refrigerant according to control of the control unit, and the control unit blocks an inflow of the refrigerant to the indoor heat exchanger during an outdoor defrosting operation for defrosting the outdoor heat exchanger, and operates the refrigeration cycle circuit using the refrigeration-facility heat exchanger as an evaporator and the outdoor heat exchanger as a gas cooler or a radiator.

Description

Technical Field

The present disclosure relates to a refrigeration system.

Background Art

Patent Literature 1 discloses an air conditioner capable of executing a defrosting operation while preventing a decrease in heating capacity. In the air conditioner, a heat storage tank is provided in a compressor of an outdoor unit, and the outdoor unit is defrosted during a heating operation, using waste heat of the compressor accumulated in the heat storage tank.
Patent Literature 2 discloses a refrigeration system including a cascade heat exchanger that exchanges heat between a low-pressure side of an air-conditioning refrigerant circuit and a high-pressure of a refrigerant circuit for a refrigeration storage facility, in which, during a cooling operation of the air-conditioning refrigerant circuit, the refrigerant on the high-pressure side of the refrigerant circuit for a refrigeration storage facility flows through a cascade heat exchanger through the condenser, and during a heating operation of the air-conditioning refrigerant circuit, the refrigerant on the high-pressure side of the refrigerant circuit for a refrigeration storage facility flows through the cascade heat exchanger and then flows through the condenser.
Patent Literature 3 discloses a heat source unit and a refrigeration apparatus that prevent a situation in which a gas refrigerant in a gas-liquid separator cannot be sent to an intermediate flow path when the outside-air temperature is high. In the heat source unit and the refrigeration apparatus, when a first condition is satisfied in which an medium pressure corresponding to a pressure in the intermediate flow path is greater than a predetermined value during operations of a first compressor, a second compressor, and a third compressor, a control unit executes a first operation to increase a rotation speed of the third compressor.

Citation List

Patent Literature

Patent Literature 1: Japanese Patent No. 4666111
Patent Literature 2: Japanese Patent No. 4169638
Patent Literature 3: Japanese Patent Laid-Open No. 2022-039365

Summary of Invention

Technical Problem

A first object of the present disclosure is to disclose a refrigeration system capable of efficiently executing a defrosting operation while preventing a decrease in heating capacity.
A second object of the present is to provide a refrigeration system in which defrosting of the refrigeration-facility unit is performed by flowing a warm refrigerant, thereby saving energy.
A third object of the present disclosure is to provide a refrigeration system including a refrigeration circuit with a simple configuration, and capable of improving a refrigeration capacity.

Solution to Problem

The present application incorporates the disclosure of Japanese Patent Application No. 2022-183978, filed on November 17, 2022 in its entirety.
A refrigeration system according to a first aspect corresponding to the first object of the present disclosure includes: a refrigeration cycle circuit that connects an outdoor unit including a compressor and an outdoor heat exchanger, an indoor unit including an indoor heat exchanger, and a refrigeration-facility unit including a refrigeration-facility heat exchanger; and a control unit, the refrigeration cycle circuit includes a switching mechanism that switches a flow path of a refrigerant according to control of the control unit, and the control unit blocks an inflow of the refrigerant to the indoor heat exchanger during an outdoor defrosting operation for defrosting the outdoor heat exchanger, and operates the refrigeration cycle circuit using the refrigeration-facility heat exchanger as an evaporator and the outdoor heat exchanger as a gas cooler or a radiator.
The present application incorporates the disclosure of Japanese Patent Application No. 2023-038004, filed on March 10, 2023 in its entirety.
A refrigeration system according to a second aspect corresponding to the second object of the present disclosure includes a refrigeration cycle circuit that connects an outdoor unit including a compressor, an outdoor heat exchanger, an outdoor expansion mechanism, and an outdoor fan, an indoor unit including an indoor heat exchanger, an indoor expansion mechanism, and an indoor fan, and a refrigeration-facility unit including the refrigeration-facility heat exchanger and refrigeration-facility expansion mechanism, and a defrosting pipe is provided to connect a pipe between the refrigeration-facility heat exchanger and the compressor and a pipe between the indoor expansion mechanism and the outdoor expansion mechanism, and a defrosting on-off valve is provided in a middle of the defrosting pipe to be opened during a defrosting operation.
The present application incorporates the disclosure of Japanese Patent Application No. 2023-142103, filed on September 1, 2023 in its entirety.
A refrigeration system according to a third aspect corresponding to the third object of the present disclosure includes a refrigeration circuit provided with a plurality of compressors, a heat source-side heat exchanger, a plurality of utilization-side heat exchangers, and a gas-liquid separator, the plurality of compressors includes a low-stage compressor and a high-stage compressor, the plurality of utilization-side heat exchangers includes a first utilization-side heat exchanger and a second utilization-side heat exchanger having a refrigerant evaporation temperature lower than that of the first utilization-side heat exchanger, the refrigeration circuit is provided with a switching mechanism that causes the refrigerant, which is discharged from the high-stage compressor and flows through at least one of the heat source-side heat exchanger and the first utilization-side heat exchanger, to flow to the gas-liquid separator, and a throttling mechanism is provided between the heat source-side heat exchanger, the first utilization-side heat exchanger, and the gas-liquid separator.

Advantageous Effects of Invention

The refrigeration system according to the first aspect of the present disclosure executes an outdoor defrosting operation by blocking a refrigerant flowing through an indoor heat exchanger and using a refrigeration-facility heat exchanger as an evaporator. In addition, the heat amount can be concentrically used to raise the temperature of the outdoor heat exchanger, and the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently defrost the outdoor heat exchanger while preventing a decrease in heating capacity without using the indoor heat exchanger as an evaporator.
According to the refrigeration system of the second aspect of the present disclosure, during the defrosting operation in the cooling operation, the relatively warm refrigerant sent from the outdoor heat exchanger can be used for defrosting of the refrigeration-facility heat exchanger, and during the cooling operation, the liquid return to the compressor can be prevented using the indoor heat exchanger as an evaporator. On the other hand, during the defrosting operation in the heating operation, the relatively warm refrigerant sent from the indoor heat exchanger can be used for defrosting of the refrigeration-facility heat exchanger, and the liquid return to the low-stage compressor can be prevented using the outdoor heat exchanger as an evaporator. Therefore, an electric heater is no longer necessary unlike the related art, energy efficiency can be improved, and the reliability of the compressor can be improved by preventing the liquid return of the refrigerant.
According to the refrigeration system of the third aspect of the present disclosure, the refrigeration system includes a refrigeration circuit with a simple configuration, and is capable of stable operation.

Brief Description of Drawings

[FIG. 1] FIG. 1 is a circuit diagram of a refrigeration system according to a first embodiment showing an operation during a cooling operation.
[FIG. 2] FIG. 2 is a block diagram of the refrigeration system.
[FIG. 3] FIG. 3 is a circuit diagram of a refrigeration system according to the first embodiment showing an operation during a heating operation.
[FIG. 4] FIG. 4 is a circuit diagram of a refrigeration system according to the first embodiment showing a heating operation when the amount of heat exhausted from a refrigeration-facility unit is insufficient.
[FIG. 5] FIG. 5 is a circuit diagram of the refrigeration system according to the first embodiment showing an operation when a large capacity is required in a refrigeration-facility unit and a heat quantity for heating is not required.
[FIG. 6] FIG. 6 is a flowchart of the refrigeration system.
[FIG. 7] FIG. 7 is a graph of a first outdoor defrost line and a second outdoor defrost line.
[FIG. 8] FIG. 8 is a diagram showing a refrigeration cycle circuit of the refrigeration system after step SA4.
[FIG. 9] FIG. 9 is a diagram showing a refrigeration cycle circuit of the refrigeration system after step SA7.
[FIG. 10] FIG. 10 is a circuit diagram showing a refrigeration system according to a second embodiment showing an operation during a cooling operation.
[FIG. 11] FIG. 11 is a block diagram showing a control configuration according to the second embodiment.
[FIG. 12] FIG. 12 is a circuit diagram of the refrigeration system showing a defrosting operation during a cooling operation according to the second embodiment.
[FIG. 13] FIG. 13 is a flowchart showing the defrosting operation during the cooling operation according to the second embodiment.
[FIG. 14] FIG. 14 is a circuit diagram showing the refrigeration system according to the second embodiment showing an operation during a heating operation.
[FIG. 15] FIG. 15 is a circuit diagram of the refrigeration system showing the defrosting operation during the heating operation according to the second embodiment.
[FIG. 16] FIG. 16 is a diagram showing a refrigeration circuit of a refrigeration system according to a third embodiment.
[FIG. 17] FIG. 17 is a block diagram of the refrigeration system.
[FIG. 18] FIG. 18 is a circuit diagram showing a refrigeration circuit of a refrigeration system during a heating operation.
[FIG. 19] FIG. 19 is a circuit diagram showing a refrigeration circuit of a refrigeration system during a heating operation.
[FIG. 20] FIG. 20 is a circuit diagram showing a refrigeration circuit of a refrigeration system during a heating operation.
[FIG. 21] FIG. 21 is a p-h chart showing a state of a refrigerant in the refrigeration circuit.
[FIG. 22] FIG. 22 is a flowchart showing an operation of the refrigeration system.
[FIG. 23] FIG. 23 is a circuit diagram showing a refrigeration circuit of a refrigeration system in refrigerant recovery/vacuuming work.
[FIG. 24] FIG. 24 is a circuit diagram showing a refrigeration circuit of a refrigeration system in refrigerant filling work.
[FIG. 25] FIG. 25 is a circuit diagram showing a refrigeration circuit of a refrigeration system in a regulation operation.

Description of Embodiments

Embodiments will be described in detail below with reference to the drawings. However, unnecessarily detailed descriptions will be avoided. For example, a detailed description of a well-known matter or a redundant description of a substantially identical structure may be avoided. This is to avoid rendering a related description unduly lengthy and to thereby facilitate understanding by those skilled in the art.
The following description and the accompanying drawings are provided to allow those skilled in the art to fully understand the present disclosure, and are not intended to limit the scope of the claims.

(First Embodiment)

(Findings on which present disclosure is based)

At the time when the inventors have conceived of a refrigeration system according to a first aspect of the present disclosure, a technique has been proposed for defrost an outdoor heat exchanger in an air conditioner utilizing heat stored in a heat storage tank of a compressor. Thus, an indoor heat exchanger is not used as an evaporator, and the outdoor heat exchanger can perform a defrosting operation while performing a heating operation, whereby a decrease in heating capacity can be prevented.
However, in an air conditioner that performs defrosting of an outdoor heat exchanger while executing a heating operation, a heat quantity is required for both heating by an indoor heat exchanger and defrost of the outdoor heat exchanger. Therefore, the present inventors have found a problem that there is room for improving the efficiency of the defrosting operation, and have come up with the subject matter of the present disclosure in order to solve these problems.
In view of this, the present disclosure discloses a refrigeration system that can efficiently perform a defrosting operation while preventing a decrease in heating capacity.
Hereinafter, a first embodiment corresponding to a first aspect of the present disclosure will be described with reference to the drawings.

[1-1-1. Configuration of Refrigeration System]

FIG. 1 is a diagram showing a refrigeration cycle circuit of a refrigeration system 1 according to a first embodiment.
As shown in FIG. 1, the refrigeration system 1 includes an outdoor unit 10, an indoor unit 20, and a refrigeration-facility unit 30.
The indoor unit 20 performs air conditioning on an interior of a store, for example, a convenience store or a supermarket, and the refrigeration-facility unit 30 performs cooling on an interior of a refrigerating display showcase or a freezing display showcase that serves as a cooling storage facility installed in the store.
The outdoor unit 10 includes a low-stage compressor 11 and two high-stage compressors 12 and 12. The two high-stage compressors 12 are connected in parallel to the low-stage compressor 11.
An accumulator 13 is disposed between the low-stage compressor 11 and the high-stage compressor 12.
In other words, a refrigerant discharged from the low-stage compressor 11 is separated into gas and liquid by the accumulator 13, and only the gas refrigerant is sent to the high-stage compressor 12.
An oil separator 14 is connected to a discharge side of the high-stage compressor 12. An outdoor heat exchanger 15 is connected to the oil separator 14 through a refrigerant pipe 40. An outdoor fan 18 is provided near the outdoor heat exchanger 15.
A first heating pipe 41, which is connected to the refrigerant pipe 40 between the indoor unit 20 and the accumulator 13, is connected to the refrigerant pipe 40 between the oil separator 14 and the outdoor heat exchanger 15.
In addition, a first outdoor return pipe 42, which is connected to the refrigerant pipe 40 between the refrigeration-facility unit 30 and the low-stage compressor 11, is connected to the refrigerant pipe 40 between the oil separator 14 and the outdoor heat exchanger 15.
A first switching mechanism (switching mechanism) 50 is provided between the oil separator 14 and the outdoor heat exchanger 15. The first switching mechanism 50 includes a first cooling valve 51 that opens and closes the refrigerant pipe 40 between the oil separator 14 and the outdoor heat exchanger 15, a first heating valve 52 that is provided in a middle of the first heating pipe 41 to open and close the first heating pipe 41, and an outdoor refrigerant return valve 53 that is provided in a middle of the first outdoor return pipe 42 to open and close the first outdoor return pipe 42.
A gas-liquid separator 16 is connected to the outdoor heat exchanger 15 through the refrigerant pipe 40. A refrigeration-facility heat exchanger 31 of the refrigeration-facility unit 30 is connected to the gas-liquid separator 16 through the refrigerant pipe 40 and an inlet-side refrigeration-facility expansion mechanism 32. A refrigeration-facility fan 38 is provided near the refrigeration-facility heat exchanger 31. The refrigeration-facility heat exchanger 31 is connected to the low-stage compressor 11 through an outlet-side refrigeration-facility pressure adjustment mechanism 33.
A second cooling pipe 43, which is connected to the indoor heat exchanger 22 through an indoor expansion mechanism 21, is connected to the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16.
A second heating pipe 44, which is connected to the indoor heat exchanger 22, is connected to the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16.
A second outdoor return pipe 45, which is connected to the refrigerant pipe 40 between the refrigeration-facility heat exchanger 31 and the gas-liquid separator 16, is connected to the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16.
A second switching mechanism (switching mechanism) 54 is provided between the outdoor heat exchanger 15 and the gas-liquid separator 16. The second switching mechanism 54 includes a second cooling valve 55 that opens and closes the refrigerant pipe 40 between the outdoor heat exchanger 15 and the gas-liquid separator 16, a third cooling valve 56 that is provided in a middle of the second cooling pipe 43 to open and close the second cooling pipe 43, a second heating valve 57 that is provided in a middle of the second heating pipe 44 to open and close the second heating pipe 44, and a refrigerant return expansion mechanism 58. The refrigerant return expansion mechanism 58 is provided in a middle of the second outdoor return pipe 45 to control a flow rate of the second outdoor return pipe 45.
Check valves 59 are provided downstream of the second cooling valve 55, the third cooling valve 56, and the second heating valve 57, respectively.
The indoor heat exchanger 22 is connected to the high-stage compressor 12 through the refrigerant pipe 40, an on-off valve 23, and the accumulator 13. An indoor fan 28 is provided near the indoor heat exchanger 22.
In the present embodiment, a gas refrigerant return pipe 60 is provided to send a gas refrigerant from the gas-liquid separator 16 to a suction side of the accumulator 13. A gas refrigerant flow-rate control valve 61 is provided in a middle of the gas refrigerant return pipe 60.

[1-1-2. Configuration outside Refrigeration Cycle Circuit]

The outdoor unit 10 includes an outside air temperature sensor 17 and an outdoor defrost detection sensor 19 outside the refrigeration cycle circuit (see FIG. 2). The outside air temperature sensor 17 is a sensor that detects an outside air temperature T. The outdoor defrost detection sensor 19 is a sensor that detects a liquid temperature or a gas temperature of the refrigerant flowing through the outdoor heat exchanger 15.
The indoor unit 20 includes an indoor refrigerant temperature sensor 26 and a blowout air temperature sensor 27. The indoor refrigerant temperature sensor 26 detects a temperature of the refrigerant flowing into the indoor heat exchanger 22 and a temperature of the refrigerant flowing out from the indoor heat exchanger 22. The blowout air temperature sensor 27 is provided near an air blowing outlet of the indoor unit 20 to detect a temperature of air blown out from the indoor unit 20.
The refrigeration-facility unit 30 includes an interior temperature sensor 37 and a refrigeration-facility-unit defrost detection sensor 39. The interior temperature sensor 37 is a sensor that detects an interior temperature Tb of the refrigeration-facility unit 30. The refrigeration-facility-unit defrost detection sensor 39 is a sensor that detects a liquid temperature and a gas temperature of the refrigerant flowing through the refrigeration-facility heat exchanger 31.
In addition, the outdoor unit 10, the indoor unit 20, and the refrigeration-facility unit 30 are provided with an outdoor fan 18, an indoor fan 28, and a refrigeration-facility fan 38, respectively (see FIG. 2). The fans 18, 28, and 38 flow air through the outdoor heat exchanger 15, the indoor heat exchanger 22, and the refrigeration-facility heat exchanger 31, respectively, and facilitate heat exchange between the air and the refrigerant in the respective heat exchangers 15, 22, and 31, respectively.

[1-1-2. Configuration of Control System of Refrigeration System]

FIG. 2 is a block diagram of the refrigeration system 1, and shows a configuration of a control system of the refrigeration system 1.
As shown in FIG. 2, the outdoor unit 10 includes a control device 90 and an outdoor unit I/F 95. The control device 90 includes a control unit 91 and a storage unit 93.
The control unit 91 is a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) that operates based on a program stored in advance in the storage unit 93. The control unit 91 may be configured with a single processor or may be configured with a plurality of processors. A DSP (digital signal processor) or the like may be used as the control unit 91. Furthermore, the control circuit such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programming Gate Array) can be used as the control unit 91.
The control unit 91 is connected to the storage unit 93, the low-stage compressor 11, and the like, and controls these units.
The control unit 91 reads the computer program stored in the storage unit 93 and operates according to the read computer program, thereby functioning as a determination unit 91a and an operation control unit 91b.
The determination unit 91a compares various temperature detection values, such as a detection value of an interior temperature Tb from an interior temperature sensor 37, with various temperature data in setting data 93a stored in the storage unit 93.
The operation control unit 91b controls various devices such as the low-stage compressor 11 and the high-stage compressor 12 in the outdoor unit 10. In addition, the operation control unit 91b transmits control signals to the indoor unit 20 and the refrigeration-facility unit 30 through the outdoor unit I/F 95 to cooperatively operate the refrigeration system 1.
The storage unit 93 includes a memory device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. In addition, the storage unit 93 stores computer programs, databases, tables, and the like used for various operations of the refrigeration system 1. These computer programs may be installed in the storage unit 93 from a computer-readable portable recording medium using a known setup program, for example. The portable recording medium may be, for example, a semiconductor storage device including a CD-ROM (compact disc read only memory), a DVD-ROM (digital versatile disc read only memory), a USB (Universal Serial Bus) memory, or an SSD (Solid State Drive). The computer programs may be installed from a predetermined server, for example.
Furthermore, the storage unit 93 may include a volatile storage region and may form a work area for the control unit 91.
The storage unit 93 stores setting data 93a. The setting data 93a includes data on a setting temperature (setting value) T5 of the interior temperature Tb of the refrigeration-facility unit 30 and data on a control upper-limit temperature (first temperature) T1 of the interior temperature Tb. The control upper-limit temperature T1 is higher than the setting temperature T5. The setting data 93a also includes data on a first outdoor defrost line L1, a second outdoor defrost line L2, a defrost time D, and an outdoor defrost end temperature T2, which will be described below.
The outdoor unit I/F 95 includes communication hardware such as a communication interface circuit or a connector for the outdoor unit 10 to communicate with each device via a cable according to a predetermined communication protocol. The outdoor unit I/F 95 sends data received from each device to the control device 90, and transmits data received from the control device 90 to each device.
The indoor unit 20 includes an indoor-unit control device 80 and an indoor unit I/F 85. The indoor-unit control device 80 includes an indoor-unit control unit 81 and an indoor-unit storage unit 83.
The indoor-unit control unit 81 is a processor such as a CPU or an MPU, similarly to the control unit 91. The indoor-unit control unit 81 operates according to a computer program stored in the indoor-unit storage unit 83 to control various devices such as an indoor fan 28 mounted in the indoor unit 20. In addition, the indoor-unit control unit 81 receives output signals from various sensors mounted on the indoor unit 20 such as the blowout air temperature sensor 27.
Similarly to the storage unit 93, the indoor-unit storage unit 83 includes a storage device such as a RAM or a ROM, and stores computer programs and the like used for various operations of the indoor unit 20.
The indoor unit I/F 85 includes communication hardware such as a communication interface circuit or a connector for the indoor unit 20 to communicate with each device. The indoor unit I/F 85 sends data received from each device to the indoor-unit control device 80, and transmits data received from the indoor-unit control device 80 to each device.
The refrigeration-facility unit 30 includes a refrigeration-facility-unit control device 70 and a refrigeration-facility unit I/F 75. The refrigeration-facility-unit control device 70 includes a refrigeration-facility-unit control unit 71 and a refrigeration-facility-unit storage unit 73.
Similarly to the control unit 91, the refrigeration-facility-unit control unit 71 is a processor such as a CPU or an MPU. The refrigeration-facility-unit control unit 71 operates according to a computer program stored in the refrigeration-facility-unit storage unit 73 to control various devices such as a refrigeration-facility fan 38 mounted in the refrigeration-facility unit 30. In addition, the refrigeration-facility-unit control unit 71 receives output signals from various sensors mounted on the refrigeration-facility unit 30 such as the interior temperature sensor 37.
Similarly to the storage unit 93, the refrigeration-facility-unit storage unit 73 includes a storage device such as a RAM or a ROM, and stores computer programs and the like used for various operations of the refrigeration-facility unit 30.
The refrigeration-facility unit I/F 75 includes communication hardware such as a communication interface circuit or a connector for the refrigeration-facility unit 30 to communicate with each device. The refrigeration-facility unit I/F 75 sends data received from each device to the refrigeration-facility-unit control device 70, and transmits data received from the refrigeration-facility-unit control device 70 to each device.

[1-2. Operation]

Next, the operation of the refrigeration system 1 of the present embodiment will be described.

[1-2-1. Operation in Each Operation Mode]

First, a cooling operation will be described.
During a cooling operation, as shown in FIG. 1, the first cooling valve 51 is opened, and the second cooling valve 55 and the third cooling valve 56 are opened. The first heating valve 52, the second heating valve 57, the outdoor refrigerant return valve 53, and the refrigerant return expansion mechanism 58 are closed.
In this state, the low-stage compressor 11 and each of the high-stage compressors 12 are driven, whereby the refrigerant compressed by the low-stage compressor 11 is sent to each of the high-stage compressors 12 through the accumulator 13, further compressed by each of the high-stage compressor 12, and discharged toward the oil separator 14.
The refrigerant passing through the oil separator 14 is sent to the outdoor heat exchanger 15 through the first cooling valve 51, and exchanges heat with outside air in the outdoor heat exchanger 15.
The refrigerant after heat exchange is sent to the gas-liquid separator 16 through the second cooling valve 55, and sent to the indoor heat exchanger 22 through the third cooling valve 56.
The refrigerant exchanges heat with indoor air in the indoor heat exchanger 22 to cool the indoor air. The refrigerant subjected to heat exchange with the indoor air is returned to each of the high-stage compressors 12 through the accumulator 13.
On the other hand, some of the refrigerant from the gas-liquid separator 16 is sent to the refrigeration-facility heat exchanger 31 through the inlet-side refrigeration-facility expansion mechanism 32, and is subjected to heat exchange in the refrigeration-facility heat exchanger 31 to cool the refrigeration-facility unit 30. The refrigerant subjected to heat exchange in the refrigeration-facility heat exchanger 31 is returned to the low-stage compressor 11 through the outlet-side refrigeration-facility pressure adjustment mechanism 33.
Next, a heating operation will be described.
FIG. 3 is a circuit diagram of the refrigeration system 1 showing a heating operation. A flow of the refrigerant is indicated by arrows in the drawing.
As shown in FIG. 3, during the heating operation, the first heating valve 52 and the second heating valve 57 are opened, and the first cooling valve 51, the second cooling valve 55, the third cooling valve 56, and the outdoor refrigerant return valve 53 are closed.
In this state, the low-stage compressor 11 and each of the high-stage compressors 12 are driven, whereby the refrigerant compressed by the low-stage compressor 11 is sent to each of the high-stage compressors 12 through the accumulator 13, further compressed by each of the high-stage compressor 12, and discharged toward the oil separator 14.
The refrigerant passing through the oil separator 14 is sent to the indoor heat exchanger 22 through the first heating valve 52, and exchanges heat with indoor air in the indoor heat exchanger 22 to heat the indoor air.
The refrigerant subjected to heat exchange in the indoor heat exchanger 22 is sent to the gas-liquid separator 16 through the second heating valve 57, is then sent to the refrigeration-facility heat exchanger 31 through the inlet-side refrigeration-facility expansion mechanism 32, and is subjected to heat exchange in the refrigeration-facility heat exchanger 31 to cool the refrigeration-facility unit 30.
The refrigerant subjected to heat exchange in the refrigeration-facility heat exchanger 31 is returned to the low-stage compressor 11 through the outlet-side refrigeration-facility pressure adjustment mechanism 33.
In other words, the refrigeration system 1 of the present disclosure is configured such that during heating, the indoor heat exchange 22 functions as a gas cooler or a radiator and the outdoor heat exchanger 15 is not used.
Next, an operation will be described in a case where a heating operation is performed when the amount of heat exhausted from the refrigeration-facility unit 30 is insufficient.
FIG. 4 is a circuit diagram of the refrigeration system 1 showing a heating operation when the amount of heat exhausted from the refrigeration-facility unit 30 is insufficient. A flow of the refrigerant is indicated by arrows in the drawing.
As shown in FIG. 4, during a heating operation at full capacity, the first heating valve 52, the second heating valve 57, the outdoor refrigerant return valve 53, and the refrigerant return expansion mechanism 58 are opened, and the first cooling valve 51, the second cooling valve 55, and the third cooling valve 56 are closed.
In this state, the low-stage compressor 11 and each of the high-stage compressors 12 are driven, whereby the refrigerant compressed by the low-stage compressor 11 is sent to each of the high-stage compressors 12, further compressed by each of the high-stage compressor 12, and discharged toward the oil separator 14.
The refrigerant passing through the oil separator 14 is sent to the indoor heat exchanger 22 through the first heating valve 52, and exchanges heat with indoor air in the indoor heat exchanger 22 to heat the indoor air.
The refrigerant subjected to heat exchange in the indoor heat exchanger 22 is sent to the gas-liquid separator 16 through the second heating valve 57, and is then sent to the refrigeration-facility heat exchanger 31 through the inlet-side refrigeration-facility expansion mechanism 32. The refrigerant, which is subjected to cool the refrigeration-facility unit 30, and is subjected to heat exchange in the refrigeration-facility heat exchanger 31 is adjusted to have the same pressure as the refrigerant sent from the first outdoor return pipe 42 through the outlet-side refrigeration-facility pressure adjustment mechanism 33, and is returned to the low-stage compressor 11. This is the operation when the outside air temperature is lower than the interior temperature of the refrigeration-facility unit 30.
On the other hand, some of the refrigerant from the gas-liquid separator 16 is sent to the outdoor heat exchanger 15 through the refrigerant return expansion mechanism 58, subjected to heat exchange in the outdoor heat exchanger 15, and then returned to the low-stage compressor 11.
Thus, exhaust heat from the refrigeration-facility heat exchanger 31 and heat pumped up by the outdoor heat exchanger 15 can be used as heat for the indoor heat exchanger 22, thereby increasing the heating capacity when the amount of heat exhausted from the refrigeration-facility unit 30 is insufficient.
Next, an operation will be described in a case where a large capacity is required in the refrigeration-facility unit 30 and a heat quantity for heating is not required.
FIG. 5 is a circuit diagram of the refrigeration system 1 showing an operation when a large capacity is required in the refrigeration-facility unit 30 and a heat quantity for heating is not required. A flow of the refrigerant is indicated by arrows in the drawing.
As shown in FIG. 5, when a large capacity is required in the refrigeration-facility unit 30 and a heat quantity for heating is not required, the first cooling valve 51, the second cooling valve 55, the first heating valve 52, and the second heating valve 57 are opened, and the outdoor refrigerant return valve 53 and the third cooling valve 56 are closed.
In this state, the low-stage compressor 11 and each of the high-stage compressors 12 are driven, whereby the refrigerant compressed by the low-stage compressor 11 is sent to each of the high-stage compressors 12, further compressed by each of the high-stage compressor 12, and discharged toward the oil separator 14.
The refrigerant passing through the oil separator 14 is sent to the outdoor heat exchanger 15 through the first cooling valve 51, and exchanges heat with outside air in the outdoor heat exchanger 15.
The refrigerant after heat exchange is sent to the gas-liquid separator 16 through the second cooling valve 55.
On the other hand, the refrigerant passing through the oil separator 14 is sent to the indoor heat exchanger 22 through the first heating valve 52, exchanges heat with indoor air in the indoor heat exchanger 22 to heat the indoor air.
The refrigerant subjected to heat exchange in the indoor heat exchanger 22 interflows with the refrigerant sent from the outdoor heat exchanger 15 through the second heating valve 57, and is sent to the gas-liquid separator 16.
The refrigerant from the gas-liquid separator 16 is sent to the refrigeration-facility heat exchanger 31 through the inlet-side refrigeration-facility expansion mechanism 32. The refrigerant, which is subjected to cool the refrigeration-facility unit 30, and is subjected to heat exchange in the refrigeration-facility heat exchanger 31 is returned to the low-stage compressor 11 through the outlet-side refrigeration-facility pressure adjustment mechanism 33. Furthermore, by absorbing heat through the outdoor heat exchanger 15, the outdoor heat exchanger 15 is heated, and thus frost adhering to the outdoor heat exchanger 15 can be removed.
In the present embodiment, the gas refrigerant return pipe 60 is provided to send the gas refrigerant from the gas-liquid separator 16 to the suction side of the accumulator 13. Then, the return amount of the gas refrigerant from the gas-liquid separator 16 is controlled by control of the opening degree of the gas refrigerant flow-rate control valve 61, whereby a differential pressure of the refrigerant sent to the indoor heat exchanger 22 can be generated.
Thus, it is possible to control the pressure by adding a specified value to the evaporation temperature of the indoor heat exchanger 22 having a high evaporation temperature. Thus, it is possible to improve efficiency of an air conditioning temperature zone, which is a weak point, using carbon dioxide (R744), a natural refrigerant with high environmental preservation characteristics, and to improve the efficiency of the entire refrigeration system.

[1-2-2. Series of Operations during defrosting Operation]

Next, a series of operations will be described when the refrigeration system 1 performs a defrosting operation of the outdoor heat exchanger 15 and the refrigeration-facility heat exchanger 31. FIG. 6 is a flowchart of the refrigeration system 1 and shows a series of operations of the control unit 91 in a case of performing defrost of the outdoor heat exchanger 15 during the heating operation of the indoor heat exchanger 22.
During the heating operation of the indoor unit 20, normally, as shown in FIG. 3, the refrigerant does not flow into the outdoor unit 10, and only the refrigeration-facility heat exchanger 31 is used as an evaporator. Therefore, the heat amount for the heating operation of the indoor unit 20 may be insufficient.
In step SA1, the determination unit 91a determines whether the heat amount for the heating operation of the indoor unit 20 is insufficient. Specifically, the determination unit 91a receives the detection value of the blowout air temperature from the indoor unit 20 by the blowout air temperature sensor 27 at a predetermined time interval. Every time the determination unit 91a receives the detection value of the blowout air temperature, it determines whether the received detection value of the blowout air temperature reaches a temperature required for the heating operation of the indoor unit 20. At this time, when the received detection value of the blowout air temperature is lower than the temperature required for the heating operation of the indoor unit 20, the determination unit 91a determines that the heat amount for the heating operation is insufficient (step SA1: YES), and the process proceeds to step SA2.
In step SA2, the operation control unit 91b controls the first switching mechanism 50 and the second switching mechanism 54, and operates the outdoor heat exchanger 15 as an evaporator. Specifically, the operation control unit 91b opens the outdoor refrigerant return valve 53 of the first switching mechanism 50 and the refrigerant return expansion mechanism 58 of the second switching mechanism 54 from the state shown in FIG. 3, and sets the refrigeration cycle circuit in the state shown in FIG. 4. Thus, the heat amount for the heating operation of the indoor unit 20 is secured. Further, the temperature of the outdoor heat exchanger 15 lowers.
In step SA3, the determination unit 91a determines whether a defrost start condition is satisfied. The defrost start condition is determined by a relationship between a detection value of a lower refrigerant temperature Ta, out of the liquid temperature or the gas temperature of the refrigerant in the outdoor heat exchanger 15, detected by the outdoor defrost detection sensor 19, and the detection value of the outside air temperature T detected by the outside air temperature sensor 17. The determination unit 91a monitors the detection values of the outside air temperature T and the refrigerant temperature Ta. In addition, the determination unit 91a reads out the first outdoor defrost line L1 and the second outdoor defrost line L2 of the setting data 93a from the storage unit 93.
FIG. 7 is a graph showing the first outdoor defrost line L1 and the second outdoor defrost line L2. In FIG. 7, a horizontal axis represents an outside temperature T, and a vertical axis represents a refrigerant temperature Ta, a first condition temperature TH, and a second condition temperature TL. Both the first outdoor defrost line L1 and the second outdoor defrost line L2 are functions of the outside air temperature T, and the first condition temperature TH and the second condition temperature TL can be read by substituting the outside air temperature T. For example, when the outside temperature T is 10°C, the first condition temperature TH is -1°C, and the second condition temperature TL is -3°C.
In step SA3, the determination unit 91a applies the outside air temperature T to the read first outdoor defrost line L1 and second outdoor defrost line L2, and reads the first condition temperature TH and the second condition temperature TL. For example the determination unit 91a determines that the defrost start condition is satisfied (step SA3: YES) when a cumulative time is 60 minutes or more during which the refrigerant temperature Ta is equal to or lower than the first condition temperature TH, or an event occurs two or more times during which the refrigerant temperature Ta is equal to or lower than the second condition temperature TL for four minutes or more. In this case, the process proceeds to step SA4.
In step SA4, the operation control unit 91b fully closes the inlet-side refrigeration-facility expansion mechanism 32 to block the inflow of the refrigerant to the refrigeration-facility heat exchanger 31. In step SA4, the operation control unit 91b stops the refrigeration-facility fan 38 of the refrigeration-facility unit 30.
FIG. 8 is a diagram showing the refrigeration cycle circuit of the refrigeration system 1 immediately after step SA4. In FIG. 8, the flow of the refrigerant is indicated by arrows, and pipes not forming the flow path of the refrigerant are indicated by dashed lines to distinguish from each other. As shown in FIG. 8, when the inlet-side refrigeration-facility expansion mechanism 32 is fully closed, the refrigeration-facility heat exchanger 31 is no longer cooled, and the interior temperature Tb rises. At this time, in the refrigeration cycle circuit, the indoor heat exchanger 22 functions as a gas cooler or a radiator, and the outdoor heat exchanger 15 functions as an evaporator. For this reason, the heating operation continues in step SA4.
In step SA5, the determination unit 91a determines whether the interior temperature Tb exceeds the control upper-limit temperature T1. The determination unit 91a receives the detection value of the interior temperature Tb detected by the interior temperature sensor 37 at a predetermined time interval. The determination unit 91a reads out the control upper-limit temperature T1 of the setting data 93a from the storage unit 93. Every time receiving the detection value of the interior temperature Tb, the determination unit 91a compares the received detection value of the interior temperature Tb with the read control upper-limit temperature T1. At this time, when the interior temperature Tb exceeds the control upper-limit temperature T1 (step SA5: YES), the process proceeds to step SA6. The control upper-limit temperature T1 is an upper-limit temperature of the temperature range at which a deterioration (spoilage or the like) of contents contained in the refrigeration-facility unit 30 can be prevented. For example, when the setting temperature T5 is 5°C, if a differential, which is an allowable range of variation in the interior temperature Tb is 3K, the control upper-limit temperature T1 is 8°C.
In step SA6, the operation control unit 91b fully closes the first heating valve 52 and the indoor expansion mechanism 21 to block the inflow of the refrigerant to the indoor heat exchanger 22. In step SA7, the operation control unit 91b controls the first switching mechanism 50, the second switching mechanism 54, and the inlet-side refrigeration-facility expansion mechanism 32 to resume the inflow of the refrigerant to the refrigeration-facility heat exchanger 31. In step SA7, specifically, the operation control unit 91b opens the first cooling valve 51 of the first switching mechanism 50, and closes the outdoor refrigerant return valve 53. In step SA7, the operation control unit 91b opens the second cooling valve 55 of the second switching mechanism 54, and closes the refrigerant return expansion mechanism 58. Furthermore, in step SA7, the operation control unit 91b opens the inlet-side refrigeration-facility expansion mechanism 32, and resumes the operation of the refrigeration-facility fan 38.
FIG. 9 shows the refrigeration cycle circuit of the refrigeration system 1 after step SA7. In FIG. 9, the flow of the refrigerant is indicated by arrows, and pipes not forming the flow path of the refrigerant are indicated by dashed lines to distinguish from each other. As shown in FIG. 9, by steps SA6 and SA7, the refrigeration cycle circuit operates the refrigeration-facility heat exchanger 31 as an evaporator, operates the outdoor heat exchanger 15 as a gas cooler or a radiator, and no refrigerant flows into the indoor heat exchanger 22. Steps SA6 and SA7 are executed almost simultaneously, and the order in which steps SA6 and SA7 are executed may be reversed.
In step SA8, the operation control unit 91b executes an outdoor defrosting operation, which is a defrosting operation of the outdoor heat exchanger 15, in a state shown in FIG. 9. At the start of the outdoor defrosting operation, the interior temperature TB is a temperature exceeding the control upper-limit temperature T1. In step SA8, the operation control unit 91b executes a pull-down operation to lower the interior temperature Tb from a temperature exceeding the control upper-limit temperature T1 up to the setting temperature T5. During the pull-down operation, the rotation speeds of the low-stage compressor 11 and the high-stage compressor 12 are higher than during a normal operation in which the interior temperature Tb is kept steady, and the temperature of the refrigerant discharged from the low-stage compressor 11 and the high-stage compressor 12 rises. At this time, since the temperature of the refrigeration-facility heat exchanger 31 is higher compared to the normal operation, the temperature of the refrigerant evaporating in the refrigeration-facility heat exchanger 31 becomes higher. Thus, during the outdoor defrosting operation, the pull-down operation is executed, and the temperature of the outdoor heat exchanger 15 is more likely to rise, compared to the normal operation in which the interior temperature Tb is kept steady.
As shown in FIG. 9, during the outdoor defrosting operation, since the refrigerant does not flow into the indoor heat exchanger 22, the indoor heat exchanger 22 does not function as an evaporator, and the heating capacity is unlikely to decrease. During the outdoor defrosting operation, since the indoor heat exchanger 22 does not function as a gas cooler or a radiator, the high-temperature refrigerant releases heat mainly in the outdoor heat exchanger 15, and the temperature of the outdoor heat exchanger 15 is likely to rise.
In step SA9, the determination unit 91a determines whether the defrost end condition is satisfied. The detection value of the lower refrigerant temperature Ta out of the liquid temperature or the gas temperature of the refrigerant of the outdoor heat exchanger 15 is monitored. In addition, the determination unit 91a reads out the outdoor defrost end temperature T2 and the defrost time D of the setting data 93a from the storage unit 93. When the refrigerant temperature Ta is equal to or higher than the outdoor defrost end temperature T2, or when the duration of the outdoor defrosting operation exceeds the defrost time D, the determination unit 91a determines that the defrost end condition is satisfied (step SA9: YES), and the process proceeds to step SA10. The defrost time D is, for example, 12 minutes. The outdoor defrost end temperature T2 is, for example, 15°C.
In step SA10, the operation control unit 91b opens the first heating valve 52 and the indoor expansion mechanism 21 to resume the inflow of the refrigerant toward the indoor heat exchanger 22. Thus, the refrigeration cycle circuit is in the state shown in FIG. 5, in which the refrigeration-facility heat exchanger 31 operates as an evaporator, and the outdoor heat exchanger 15 and the indoor heat exchanger 22 operate as gas coolers or radiators.
In step SA11, the operation control unit 91b executes a water draining operation to remove defrost water generated by the outdoor defrosting operation in step SA8 from the outdoor heat exchanger 15 in the state in FIG. 5. At the start of step SA11, defrost water generated by melting frost may adhere to the outdoor heat exchanger 15. In the water draining operation, the operation control unit 91b operates the outdoor heat exchanger 15 as a gas cooler or a radiator to raise the temperature of the outdoor heat exchanger 15 and evaporate the defrost water. The operation control unit 91b drives the outdoor fan 18 of the outdoor unit 10 to blow air to the outdoor heat exchanger 15, thereby blowing off the defrost water adhering to the outdoor heat exchanger 15. Thus, the defrost water adhering to the outdoor heat exchanger 15 can be removed, and the defrost water can be prevented from refreezing in the outdoor heat exchanger 15. The operation control unit 91b ends the water draining operation when a predetermined time has elapsed after the start of the water draining operation, and returns to the operation during the normal heating operation.

[1-2-3. Operation during Defrosting of Refrigeration-facility Heat Exchanger]

Next, a description will be given with respect to an operation for defrosting the refrigeration-facility heat exchanger 31. The control unit 91 executes a defrosting operation (refrigeration-facility unit defrosting operation) of the refrigeration-facility heat exchanger 31 at a predetermined time interval. In hot and humid conditions such as summer, frost is likely to form on the refrigeration-facility heat exchanger 31. The refrigeration system 1 can perform the defrosting operation of the refrigeration-facility heat exchanger 31 while preventing a decrease in the capacity of the cooling operation during the summer in which frost is likely to form on the refrigeration-facility heat exchanger 31. In other words, the control unit 91 can execute the defrosting operation of the refrigeration-facility heat exchanger 31 by operating the refrigeration cycle circuit in which the indoor heat exchanger 22 operates as an evaporator and the refrigeration-facility heat exchanger 31 operates as a gas cooler or a radiator.

[1-3. Effects of Invention]

As described above, in the present embodiment, the refrigeration system 1 includes: the refrigeration cycle circuit that connects the outdoor unit 10 including the low-stage compressor 11, the high-stage compressor 12, and the outdoor heat exchanger 15, the indoor unit 20 including the indoor heat exchanger 22, and the refrigeration-facility unit 30 including the refrigeration-facility heat exchanger 31; and the control unit 91, the refrigeration cycle circuit includes the first switching mechanism 50 and the second switching mechanism 54 that switch the flow path of the refrigerant according to the control of the control unit 91, and the control unit 91 blocks the inflow of the refrigerant to the indoor heat exchanger 22 during the outdoor defrosting operation for defrosting the outdoor heat exchanger 15, and operates the refrigeration cycle circuit using the refrigeration-facility heat exchanger 31 as an evaporator and the outdoor heat exchanger 15 as a gas cooler or a radiator.
Thus, the refrigeration system 1 can operate the outdoor heat exchanger 15 as a gas cooler or a radiator without flowing the refrigerant into the indoor heat exchanger 22. In addition, the heat amount can be concentrically used to raise the temperature of the outdoor heat exchanger 15, and the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently execute the defrosting operation of the outdoor heat exchanger 15 while preventing a decrease in the heating capacity.
In the present embodiment, the refrigeration system 1 includes the interior temperature sensor 37 that detects the interior temperature Tb of the refrigeration-facility unit 30, and the control unit 91 stops the inflow of the refrigerant to the refrigeration-facility heat exchanger 31 before the start of the outdoor defrosting operation, and raises the interior temperature Tb of the refrigeration-facility unit 30 up to the control upper-limit temperature T1 that is higher than the setting temperature T5 of the interior temperature Tb.
Thus, during the outdoor defrosting operation, the refrigerant evaporates at a high temperature using the refrigeration-facility heat exchanger 31 of which temperature rises, whereby the temperature of the refrigerant supplied to the outdoor heat exchanger 15 rises, and the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently execute the defrosting operation of the outdoor heat exchanger 15 while preventing a decrease in the heating capacity.
In the present embodiment, the control unit 91 executes, during the outdoor defrosting operation, the pull-down operation to lower the interior temperature Tb from the control upper-limit temperature T1 to the setting temperature T5 of the interior temperature Tb.
Thus, the low-stage compressor 11 and the high-stage compressor 12 are operated at a high rotation speed, and the high-temperature refrigerant is supplied to the outdoor heat exchanger 15, whereby the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently execute the defrosting operation of the outdoor heat exchanger 15 while preventing a decrease in the heating capacity.
In the present embodiment, the control unit 91 operates the refrigeration cycle circuit after the end of the outdoor defrosting operation, using the indoor heat exchanger 22 and the outdoor heat exchanger 15 as a gas cooler or a radiator, and the refrigeration-facility heat exchanger 31 as an evaporator.
Thus, it is possible to remove the defrost water adhering to the outdoor heat exchanger 15 in parallel with the heating operation by the indoor unit 20. Therefore, it is possible to prevent refreezing of the defrost water in the outdoor heat exchanger 15 while preventing a decrease in the heating capacity.
In the present embodiment, the control unit 91 operates the refrigeration cycle circuit during the refrigeration-facility unit defrosting operation that performs defrosting of the refrigeration-facility heat exchanger 31, using the indoor heat exchanger 22 as an evaporator, and the refrigeration-facility heat exchanger 31 as a gas cooler or a radiator.
Thus, the refrigeration system 1 can use the indoor heat exchanger 22 as an evaporator to operate the refrigeration-facility heat exchanger 31 as a gas cooler or a radiator. Therefore, it is possible to defrost the refrigeration-facility heat exchanger 31 while preventing a decrease in the heating capacity.

(Other Embodiments)

As described above, the first embodiment has been described as examples of techniques disclosed in the present application. However, the techniques of the present disclosure are not limited thereto, and are also applicable to embodiments where changes, replacements, additions, omissions, etc., are appropriately made. In addition, it is also possible to combine the components described in the first embodiment to create new embodiments.
Hereinafter, other embodiments will be described as examples.
In step SA1 described in the first embodiment, the determination unit 91a determines, based on the detection value of the blowout air temperature sensor 27, whether the heat amount for the heating operation is insufficient, but this is merely one example. The determination unit 91a may determine, based on the detection value of the temperature of the refrigerant flowing in and out of the indoor heat exchanger 22 by the indoor refrigerant temperature sensor 26, whether the heat amount for the heating operation is insufficient.
The defrost start condition in step SA3 and the defrost end condition in step SA9 described in the first embodiment are examples, respectively, and are not limited to the conditions described in the first embodiment.
In the first embodiment, the determination unit 91a performs the determination by comparing the interior temperature Tb with the control upper-limit temperature T1 in step SA5, but this is merely an example. The determination unit 91a may compare the interior temperature Tb with a temperature that is lower than the control upper-limit temperature T1 and higher than the setting temperature T5 in step SA5. Thus, the deterioration of the contents contained in the refrigeration-facility unit 30 is easily prevented.
The configurations of the outdoor unit 10, the indoor unit 20, and the refrigeration-facility unit 30 shown in FIG. 2 are merely examples, and specific implementations are not particularly limited. Thus, hardware individually corresponding to each component does not necessarily need to be implemented, and functions of each component may be achieved by one processor executing a computer program. Some functions achieved by software in the above-described embodiments may be achieved by hardware, or some functions achieved by hardware may be achieved by software. Specific detailed components of other units of the refrigeration system 1 are optionally changeable without departing from the spirit of the present disclosure.
Step units of the operation shown in FIG. 6 are divisions according to main processing contents to facilitate understanding of operation of each unit, and the operation is not limited by a division scheme of processing units and their names. The division into a larger number of step units may be made in accordance with processing contents. The division may be made such that each step unit includes a larger number of processes. Moreover, orders of steps may be interchanged as appropriate without interference with the spirit of the present invention.

(Second Embodiment)

(Findings on which present disclosure is based)

At the time when the inventors have conceived of a refrigeration system according to a second aspect of the present disclosure, there has been a refrigeration system, in which refrigeration and freezing equipment and air conditioning equipment are combined into a single refrigeration circuit to use the exhaust heat from the refrigeration and freezing equipment for heating in the winter, in stores such as convenience stores, thereby saving energy.
In such a related art, generally, during defrosting of the refrigeration-facility unit, a thermo-off defrost system is often used in a refrigeration case, and an electric heater defrost system is often used in a freezing case.
However, the inventors have found a problem with the electric heater defrost system used for defrosting of the refrigeration case in that the electric heater requires power consumption, reducing system efficiency and making it impossible to achieve energy savings, and have come up with the subject matter of the present disclosure in order to solve this problem.
A second aspect of the present disclosure provides a refrigeration system in which defrosting of the refrigeration-facility unit is performed by flowing a warm refrigerant, thereby saving energy.
Hereinafter, the second embodiment corresponding to a second aspect of the present disclosure will be described with reference to the drawings.

[2-1-1. Configuration of Refrigeration System]

FIG. 10 is a diagram showing a refrigeration cycle circuit of a refrigeration system 101 according to the second embodiment. As shown in FIG. 10, the refrigeration cycle circuit of the refrigeration system 101 includes a defrosting pipe 162, a defrosting on-off valve 163, and a defrost sensor 164 in addition to the refrigeration cycle circuit of the refrigeration system 1 according to the first embodiment.
The refrigerant return expansion mechanism 58 in the present embodiment is provided as an outdoor expansion mechanism.
Pipes between the refrigeration-facility heat exchanger 31 and the low-stage compressor 11, and pipes between the indoor heat exchanger 22, the indoor expansion mechanism 21, and the second switching mechanism 54 are connected by a defrosting pipe 162. The defrosting on-off valve 163 is provided in the middle of the defrosting pipe 162.
The defrosting on-off valve 163 is closed during the cooling operation and the heating operation, and is opened during the defrosting operation.
In the present embodiment, the defrost sensor 164 (see FIG. 11) is provided near the refrigeration-facility heat exchanger.

[2-1-2. Control Configuration]

Next, a control configuration of the refrigeration system 101 will be described.
FIG. 11 is a block diagram showing a control configuration according to the second embodiment.
As shown in FIG. 11, the refrigeration system includes a control unit 70. The control unit 70 may be provided in the outdoor unit 10 or may be provided in the indoor unit 20.
The control unit 70 includes a processor such as a CPU or an MPU, and a storage unit. The storage unit of the control unit 70 includes a volatile memory and a nonvolatile storage unit. The volatile memory is, for example, a RAM. The nonvolatile storage unit is configured with a ROM, a hard disk, a flash memory, or the like. The control unit 70 is communicably connected to various devices of the refrigeration system 101 via wired communication means such as a signal line, or wireless communication means such as a wireless communication circuit.
The control unit 70 performs programs stored in the storage unit to control operations of the low-stage compressor 11, the high-stage compressor 12, the outdoor fan 18, the indoor fan 28, the refrigeration-facility fan 38, various expansion mechanisms 21, 32, and 58, and various valves 23, 51, 52, 53, 55, 56, and 57.

[2-2. Operation]

Next, an operation of the present embodiment will be described.
As shown in FIG. 10, the operation of the cooling operation of the refrigeration system 101 is similar to the operation of the cooling operation of the refrigeration system 1 described in the first embodiment.
Next, the operation of the defrosting operation during the cooling operation will be described.
FIG. 12 is a circuit diagram of the refrigeration system 101 showing the operation of the defrosting operation during the cooling operation. The flow of the refrigerant is indicated by arrows in the drawing.
As shown in FIG. 12, in a case of defrosting of the refrigeration-facility unit during the cooling operation, first, the defrosting on-off valve 163 is opened, and the outlet-side refrigeration-facility pressure adjustment mechanism 33 is closed.
When the refrigeration system is operated, as indicated by the arrows in the drawing, the refrigerant compressed and discharged by the low-stage compressor 11 and the high-stage compressor 12 is sent to the refrigeration-facility heat exchanger 31 through the oil separator 14, the outdoor heat exchanger 15, and the refrigerant return expansion mechanism 58.
Such a refrigerant is a relatively warm refrigerant sent from the outdoor heat exchanger 15, and can be used for defrosting of the refrigeration-facility heat exchanger 31.
Then, the refrigerant discharged from the refrigeration-facility heat exchanger 31 flows into the indoor heat exchanger 22 through the defrosting pipe 162. The refrigerant is gasified using the indoor heat exchanger 22 as an evaporator, and is returned to the accumulator 13.
Thus, the indoor heat exchanger 22 functions as an evaporator, whereby the refrigerant is completely gasified, and a liquid return of the high-stage compressor 12 can be prevented.
FIG. 13 is a flowchart showing an operation of the defrosting operation.
As shown in FIG. 13, when the defrosting operation ends, the control unit 70 sets timer counter to measure a time from the end of the defrosting operation (SA101). The control unit 70 determines whether a predetermined time D0 has elapsed from the end of the defrosting operation (SA102). The predetermined time D0 from the end of the defrosting operation is a time when frost is considered to be formed on the refrigeration-facility heat exchanger 31, and is six hours, for example.
When it is determined that the predetermined time has elapsed from the end of the defrosting operation (SA102: YES), the control unit 70 determines whether to perform a defrost extension mode (SA103). The defrost extension mode is, for example, a mode performed when frost is considered not to be formed within a predetermined time based on conditions such as the outside air temperature.
When it is determined that the defrost extension mode is performed (SA103: YES), the control unit 70 sets an extension timer counter and starts measuring a defrost extension time (SA104). On the other hand, when it is determined that the extension mode is not performed (SA103: NO), the defrosting operation immediately starts (SA109).
Subsequently, the control unit 70 determines whether a thermo-off operation has been performed within a predetermined time DA (for example, within 30 minutes) (SA105).
When it is determined that the thermo-off operation has been performed (SA105: YES), the control unit 70 determines that heat exchange is normally performed by the refrigeration-facility heat exchanger 31, and continues the defrost extension mode. On the other hand, when it is determined that the thermo-off operation has not been performed within the predetermined time DA (SA105: NO), the control unit 70 resets an operation extension timer counter of the refrigeration-facility unit 30 (SA108), and starts the defrosting operation (SA109).
When the defrost extension mode is continued, the control unit 70 determines whether the interior temperature of the refrigeration-facility unit 30 is below a predetermined temperature DB (for example, -15°C) (SA106). When it is determined that the interior temperature of the refrigeration-facility unit 30 is below the predetermined temperature DB (SA106: YES), the control unit 70 continues the defrost extension mode. On the other hand, when it is determined that the interior temperature of the refrigeration-facility unit 30 is equal to or higher than the predetermined temperature DB (SA106: NO), the control unit 70 resets the operation extension timer counter of the refrigeration-facility unit 30 (SA108), and starts a defrosting operation (SA109).
Subsequently, the control unit 70 determines whether a predetermined time DC (for example, 4 hours) has elapsed from the start of the extension mode (SA107), and when it is determined that the predetermined time DC has elapsed (SA107: YES), the control unit resets the operation extension timer counter of the refrigeration-facility unit 30 (SA108) and starts a defrosting operation (SA109).
When the defrosting operation is started (SA109), as described above, the defrosting on-off valve 163 is opened, the outlet-side refrigeration-facility pressure adjustment mechanism 33 is closed, and the operation of the refrigeration-facility fan 38 is stopped (SA110).
Then, the control unit 70 determines whether the temperature detected by the defrost sensor 164 is equal to higher than a predetermined temperature DD (for example, 10°C) (SA111). When it is determined that the temperature detected by the defrost sensor 164 is equal to higher than the predetermined temperature DD (SA111: YES), the control unit 70 ends the defrosting operation (SA112).
When the defrosting operation ends, a water draining operation is started (SA113). In the water draining operation, the operation of the refrigeration-facility fan 38 is stopped to drop the condensed water adhering to a cooling fin of the refrigeration-facility heat exchanger 31.
Then, the control unit 70 determines whether a predetermined time DE (for example, 5 minutes) has elapsed from the end of the defrosting operation (SA114). When it is determined that the predetermined time DE has elapsed (SA114: YES), the control unit 70 closes the defrosting on-off valve 163 and opens the outlet-side refrigeration-facility pressure adjustment mechanism 33, thereby starting the cooling operation (SA115).
In the case, the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31 may be adjusted when the heat amount required for defrosting is large (for example, at the start of defrosting which is a latent heat change) and when the heat amount required for defrosting is small (for example, at the end of defrosting which is a sensible heat change, or during the water draining operation).
For example, the air flow rate by the outdoor fan 18 changes, and thus the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31 is adjusted. In this case, when the heat amount required for defrosting is large, the air flow rate by the outdoor fan 18 is reduced and a refrigerant having a relatively high temperature is sent to the refrigeration-facility heat exchanger, and when the heat amount required for defrosting is small, the air flow rate by the outdoor fan 18 is increased and a refrigerant having a relatively low temperature is sent to the refrigeration-facility heat exchanger 31.
In addition, the amount of expansion of the refrigerant by the inlet-side refrigeration-facility expansion mechanism 32 and the refrigerant return expansion mechanism 58 is adjusted, and thus the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31 may be adjusted.
For example, when the heat amount required for defrosting is large, the amount of expansion of the refrigerant by the inlet-side refrigeration-facility expansion mechanism 32 and the refrigerant return expansion mechanism 58 is reduced and a refrigerant having a relatively high temperature is sent to the refrigeration-facility heat exchanger, and when the heat amount required for defrosting is small, the amount of expansion of the refrigerant by the inlet-side refrigeration-facility expansion mechanism 32 and the refrigerant return expansion mechanism 58 is increased and a refrigerant having a relatively low temperature is sent to the refrigeration-facility heat exchanger 31.
The temperature of the refrigerant is adjusted according to the heat amount required for defrosting as described above, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger 31, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
Furthermore, during the defrosting operation, the refrigerant flow path may be switched depending on whether the heat amount required for defrosting is large or small.
Specifically, the second cooling valve 55 is opened to be switched such that the refrigerant from the outdoor heat exchanger 15 is sent to the refrigeration-facility heat exchanger 31 through the gas-liquid separator 16.
The refrigerant from the outdoor heat exchanger 15 is circulated through the gas-liquid separator 16 in this way, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger 31, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
Next, the operation during the heating operation will be described.
FIG. 14 is a circuit diagram of the refrigeration system 101 showing the operation of the heating operation. The flow of the refrigerant is indicated by arrows in the drawing.
As shown in FIG. 14, the operation of the heating operation of the refrigeration system 101 is similar to the operation of the heating operation of the refrigeration system 1 described in the first embodiment.
In the present embodiment, a gas refrigerant return pipe 60 is provided to send a gas refrigerant from the gas-liquid separator 16 to a suction side of the accumulator 13. During the cooling operation, the return amount of the gas refrigerant from the gas-liquid separator 16 is controlled by control of the opening degree of the gas refrigerant flow-rate control valve 61, whereby a differential pressure of the refrigerant sent to the indoor heat exchanger 22 can be generated.
Thus, it is possible to control the pressure by adding a specified value to the evaporation temperature of the indoor heat exchanger 22 having a high evaporation temperature. Therefore, it is possible to improve efficiency of an air conditioning temperature zone, which is a weak point, using carbon dioxide (R744), a natural refrigerant with high environmental preservation characteristics, and to improve the efficiency of the entire refrigeration system.
Next, the operation of the defrosting operation during the heating operation will be described.
FIG. 15 is a circuit diagram of the refrigeration system 101 showing the operation of the defrosting operation during the heating operation. The flow of the refrigerant is indicated by arrows in the drawing.
As shown in FIG. 15, when defrosting of the refrigeration-facility unit 30 is performed during the heating operation, first, the defrosting on-off valve 163 is opened, and the outlet-side refrigeration-facility pressure adjustment mechanism 33 is closed.
When the refrigeration system 101 is operated, as indicated by the arrows in the drawing, the refrigerant compressed and discharged by the low-stage compressor 11 and the high-stage compressor 12 is sent to the refrigeration-facility heat exchanger 31 through the oil separator 14, the indoor heat exchanger 22, and the defrosting pipe 162.
Thus, a relatively warm refrigerant sent from the indoor heat exchanger 22 can be used for defrosting of the refrigeration-facility heat exchanger 31.
Then, the refrigerant discharged from the refrigeration-facility heat exchanger 31 is sent to the outdoor heat exchanger 15, and the refrigerant is gasified using the outdoor heat exchanger 15 as an evaporator, and is returned to the low-stage compressor 11.
Thus, the outdoor heat exchanger 15 functions as an evaporator, whereby the refrigerant is completely gasified, and a liquid return of the low-stage compressor 11 can be prevented.
In this case, similarly to the cooling operation, during the heating operation, the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31 may also be adjusted depending on whether the heat amount required for defrosting is large or small.
In this case, however, although the air flow rate by the indoor fan 28 can be changed, since the heating efficiency of the indoor fan 28 needs to be given priority to a certain extent, there is a certain limit to change the air flow rate by the indoor fan 28.

[2-3. Effects]

As described above, according to the present embodiment, the refrigeration system includes the refrigeration cycle circuit that connects the outdoor unit 10 including the low-stage compressor 11 and high-stage compressor 12 (compressor), the outdoor heat exchanger 15, the refrigerant return expansion mechanism 58 (outdoor expansion mechanism), and the outdoor fan 18, the indoor unit 20 including the indoor heat exchanger 22, the indoor expansion mechanism 21, and the indoor fan 28, and the refrigeration-facility unit 30 including the refrigeration-facility heat exchanger 31, and the inlet-side refrigeration-facility expansion mechanism 32 (refrigeration-facility expansion mechanism). The defrosting pipe 162 is provided to connect the pipe between the refrigeration-facility heat exchanger 31 and the low-stage compressor 11 and the pipe between the indoor expansion mechanism 21 and the refrigerant return expansion mechanism 58, and the defrosting on-off valve 163 is provided in the middle of the defrosting pipe 162 to be opened during the defrosting operation.
Thus, in the defrosting operation during the cooling operation, the relatively warm refrigerant sent from the outdoor heat exchanger 15 can be used for defrosting of the refrigeration-facility heat exchanger 31, and the liquid return to the high-stage compressor 12 can be prevented using the indoor heat exchanger 22 as an evaporator. On the other hand, in the defrosting operation during the heating operation, the relatively warm refrigerant sent from the indoor heat exchanger 22 can be used for defrosting of the refrigeration-facility heat exchanger 31, and the liquid return to the low-stage compressor 11 can be prevented using the outdoor heat exchanger 15 as an evaporator.
Therefore, an electric heater is no longer necessary unlike the related art, energy efficiency can be improved, and the reliability of the low-stage compressor 11 or the high-stage compressor 12 can be improved by preventing the liquid return of the refrigerant.
In the present embodiment, the air flow rate by the outdoor fan 18 or the indoor fan 28 is changed depending on whether the heat amount required for defrosting of the refrigeration-facility heat exchanger 31 is large or small, thereby adjusting the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31.
Thus, the air flow rate by the outdoor fan 18 or the indoor fan 18 is changed, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger 31, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
In the present embodiment, during the defrosting of the refrigeration-facility heat exchanger 31, the amount of expansion of the refrigerant by any one of the refrigerant return expansion mechanism 58 (outdoor expansion mechanism), the indoor expansion mechanism 21, and the inlet-side refrigeration-facility expansion mechanism 32 (refrigeration-facility expansion mechanism) is changed depending on whether the heat amount required for the defrosting is large or small, whereby the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31 is adjusted.
Thus, the amount of expansion of the refrigerant by any one of the refrigerant return expansion mechanism 58, the indoor expansion mechanism 21, and the inlet-side refrigeration-facility expansion mechanism 32 is changed, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger 31, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
In the present embodiment, the gas-liquid separator 16 is provided between the outdoor heat exchanger 15, and the indoor heat exchanger and the refrigeration-facility heat exchanger, and during the defrosting of the refrigeration-facility heat exchanger, the refrigerant flow path through which the refrigerant is directly sent from the outdoor heat exchanger 15 to the refrigeration-facility heat exchanger 31 and the refrigerant flow path through which the refrigerant is sent from the outdoor heat exchanger 15 through the gas-liquid separator 16 to the refrigeration-facility heat exchanger 31 are switched depending on whether the heat amount required for the defrosting is large or small, whereby the temperature of the refrigerant flowing into the refrigeration-facility heat exchanger 31 is adjusted.
Thus, when the heat amount required for defrosting is large, the refrigerant from the outdoor heat exchanger 15 is circulated through the gas-liquid separator 16, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger 31, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.

(Other Embodiments)

As described above, the second embodiment has been described as an example of techniques disclosed in the present application. However, the techniques of the present disclosure are not limited thereto, and are also applicable to embodiments where changes, replacements, additions, omissions, etc., are appropriately made. In addition, it is also possible to combine the components described in the first and second embodiments to create new embodiments.

(Third Embodiment)

(Findings on which present disclosure is based)

At the time when the inventors have conceived of a refrigeration system according to a third aspect of the present disclosure, there has been a refrigeration system including one refrigeration circuit that is provided with a low-stage compressor, a high-stage compressor, a plurality of utilization-side heat exchangers, and a heat source-side heat exchanger shared with these utilization-side heat exchangers, the utilization-side heat exchangers being operated in different evaporation temperature zones. Thus, the refrigeration system performs, for example, air conditioning of an air-conditioned space and cooling of the interior of the refrigeration-facility unit at the same time.
There has been known that such a refrigeration system includes a gas-liquid separator. In such a refrigeration system, the refrigerant discharged from the compressor flows into the utilization-side heat exchanger through the gas-liquid separator, thereby improving a refrigeration capacity.
In the above-described refrigeration system, the utilization-side heat exchanger is switched between a cooling operation and a heating operation. In such a refrigeration system, the inventors have found a problem that the configuration of the refrigeration circuit provided in the refrigeration system is complicated in order to flow the refrigerant, which is sent from the compressor, through the gas-liquid separator to the utilization-side heat exchanger in any of these operations, and have come to form the subject of the present disclosure to solve such a problem.
In view of the above, the present disclosure provides a refrigeration system including a refrigeration circuit with a simple configuration and capable of improving a refrigeration capacity.
Hereinafter, a third embodiment corresponding to a third aspect of the present disclosure will be described with reference to the drawings.

[3-1-1. Configuration of Refrigeration System]

FIG. 16 is a circuit diagram showing a refrigeration system 201 according to a third embodiment. In FIG. 16, for the convenience of description, an opening/closing device in an open state is shown in white, and an opening/closing device in a closed state and expansion mechanism are shown in black. In FIG. 16, for the convenience of description, pipes through which a refrigerant flows are shown in thick lines, and pipes through which no refrigerant flows are shown in thin lines. In subsequent circuit diagrams, opening/closing devices and pipes are shown in the same manner as in FIG. 16.
As shown in FIG. 16, the refrigeration system 201 includes an outdoor unit 210, an indoor unit 220, and a refrigeration-facility unit 230, and these units are connected to each other by refrigerant pipes to form a refrigeration circuit 202 that functions as a flow path through which a refrigerant flows.
In the present embodiment, the refrigerant used in the refrigeration circuit 202 is, for example, refrigerant carbon dioxide (R744), a natural refrigerant that is non-flammable and non-toxic.
The indoor unit 220 includes an indoor heat exchanger 222 which is a utilization-side heat exchanger. The indoor unit 220 performs air conditioning on the interior of a store, which is an air-conditioned space, based on a setting temperature set by a user in a store such as a convenience store or a supermarket.
The refrigeration-facility unit 230 includes a refrigeration-facility heat exchanger 232 which is a utilization-side heat exchanger. The refrigeration-facility unit 230 performs cooling on an interior of a refrigerating display showcase or a freezing display showcase that serves as a cooling storage facility installed in the store, based on a setting temperature set by the user.
In the refrigeration system 201, when the setting temperature of the indoor unit 220 is set, a rotational frequency of each of the compressors and an air flow rate of blowers 218 and 228 are determined based on a temperature difference between the setting temperature and a temperature in the air-conditioned space in which the indoor unit 220 is installed. Furthermore, in the refrigeration system 201, when the setting temperature of the indoor unit 220 is set, an opening degree of a throttle valve provided in the indoor unit 220 is determined such that the degree of superheat of the refrigerant at each of an inlet side and an outlet side of the indoor heat exchanger 222 becomes a specified value. Thus, the refrigeration system 201 operates such that the air-conditioned space becomes the setting temperature.
Similarly, in the refrigeration system 201, when the setting temperature of the refrigeration-facility unit 230 is set, the rotational frequency of each of the compressors and the air flow rate of blowers 218 and 238 are determined based on a temperature difference between the setting temperature and a temperature in the interior of the showcase. Furthermore, in the refrigeration system 201, when the setting temperature of the refrigeration-facility unit 230 is set, an opening degree of a throttle valve provided in the refrigeration-facility unit 230 is determined such that the degree of superheat of the refrigerant at each of an inlet side and an outlet side of the refrigeration-facility heat exchanger 232 becomes a specified value. Thus, the refrigeration system 201 operates such that the interior of the showcase becomes the setting temperature.
Hereinafter, the operation, in which the refrigeration system 201 performs the air conditioning of the air-conditioned space and the indoor cooling of the showcase, will be referred to as a first operation mode.
The outdoor unit 210 functions as a so-called heat source device. The outdoor unit 210 is formed in such a manner that a plurality of compressors, a first switching mechanism 250, an outdoor heat exchanger 215, a second switching mechanism 254, and a gas-liquid separator 216 are sequentially connected.
The outdoor heat exchanger 215 corresponds to the "heat source-side heat exchanger" in the present disclosure.
In the present embodiment, the outdoor unit 210 is provided with a mechanism in which a low-stage compressor 211 and two high-stage compressors 212 and 212 are configured as a two-stage compressor. The two high-stage compressors 212 and 212 are both connected in series to the low-stage compressor 211. The two high-stage compressors 212 and 212 are connected in parallel to each other on a downstream side of the low-stage compressor 211.
Each of the compressors is a rotary compressor in which a compression mechanism is driven by a motor, for example. Each of the high-stage compressors 212 is driven to discharge the refrigerant at a higher discharge pressure than the low-stage compressor 211.
An accumulator 213 is disposed between the low-stage compressor 211 and the high-stage compressor 212. The accumulator 213 functions as a flow divider that distributes almost evenly oil sent from an oil separator 214 to each of the high-stage compressor 212.
The oil separator 214 is connected to a discharge side of the high-stage compressor 212. The first switching mechanism 250 is connected to the oil separator 214. In other words, the first switching mechanism 250 is connected to a discharge pipe of the high-stage compressor 212 through the oil separator 214.
The first switching mechanism 250 is a mechanism that switches the refrigerant sent from the high-stage compressor 212 in the refrigeration circuit 202 to flow through any one of a plurality of flow paths.
The first switching mechanism 250 includes a pipe 240 that connects the oil separator 214 and the outdoor heat exchanger 215. A first cooling valve 251 is provided in the pipe 240. The first cooling valve 251 is located between the high-stage compressor 212 and the outdoor heat exchanger 215 on the pipe 240. The first cooling valve 251 is an opening/closing device that opens and closes the pipe 240. In the present embodiment, the first cooling valve 251 is an opening/closing device that can be switched between an open state in which a refrigerant can flow through the pipe 240 and a closed state in which a refrigerant does not flow through the pipe 240.
On the pipe 240, one end of a first heating pipe 241 is connected between the oil separator 214 and the first cooling valve 251. A first heating valve 252 is provided in the first pipe 241. The first heating valve 252 is an opening/closing device that opens and closes the first heating pipe 241.
The other end of the first heating pipe 241 is connected to a pipe 271 that connects the indoor heat exchanger 222 of the indoor unit 220 and a suction side of the high-stage compressor 212. Thus, the discharge side of the high-stage compressor 212 is connected to the indoor heat exchanger 222 through the first heating pipe 241.
On the pipe 271, an on-off valve 223 is provided between the point, where the other end of the first heating pipe 241 is connected, and the accumulator 213. The on-off valve 223 is an opening/closing device that opens and closes the pipe 271.
On the pipe 240, one end of a first outdoor return pipe 242 is connected between the first cooling valve 251 and the outdoor heat exchanger 215. An outdoor refrigerant return valve 253 is provided in the first outdoor return pipe 242. The outdoor refrigerant return valve 253 is an opening/closing device that opens and closes the first outdoor return pipe 242. The other end of the first outdoor return pipe 242 is connected between a refrigeration-facility heat exchanger 232 of the refrigeration-facility unit 230 and a suction side of the low-stage compressor 211.
On the pipe 272, an outlet-side refrigeration-facility pressure regulation mechanism 233 is provided between the point, where the other end of the first outdoor return pipe 242 is connected, and the refrigeration-facility heat exchanger 232. The outlet-side refrigeration-facility pressure regulation mechanism 233 is an opening/closing device that can change the opening degree from a fully closed state to a fully open state. The outlet-side refrigeration-facility pressure regulation mechanism 233 functions as a so-called throttle valve that can change the pressure of the refrigerant flowing through the pipe 272 by regulating the opening degree.
As described above, the outdoor heat exchanger 215, the indoor heat exchanger 222, the refrigeration-facility heat exchanger 232, and the low-stage compressor 211 are connected to the first switching mechanism 250.
The first switching mechanism 250 switches the flow path of the refrigerant in the refrigeration circuit 202 by opening and closing the first cooling valve 251, the first heating valve 252, and the outdoor refrigerant return valve 253, and causes the refrigerant discharged from the high-stage compressor 212 to flow into either of the outdoor heat exchanger 215 and the indoor heat exchanger 222.
For example, when the refrigeration system 201 performs a cooling operation, the refrigerant discharged from the high-stage compressor 212 flows into the outdoor heat exchanger 215.
When the refrigeration system 201 performs a heating operation, the refrigerant discharged from the high-stage compressor 212 flows into the indoor heat exchanger 222. When the refrigeration system 201 performs a heating operation and the heat quantity for heating becomes excessive, the refrigerant discharged from the high-stage compressor 212 flows into each of the outdoor heat exchanger 215 and the indoor heat exchanger 222.
As described above, the first switching mechanism 250 includes the first cooling valve 251, the first heating valve 252, and the outdoor refrigerant return valve 253.
In the present embodiment, the first cooling valve 251, the first heating valve 252, and the outdoor refrigerant return valve 253 are motor-operated on-off valves that are opened and closed by an actuator or the like.
Therefore, the first switching mechanism 250 can switch the flow path of the refrigerant in the refrigeration circuit 202 without stopping the low-stage compressor 211 and the high-stage compressor 212. In other words, the refrigeration system 201 can switch operations related to air conditioning and cooling of the interior of the showcase without stopping the low-stage compressor 211 and the high-stage compressor 212.
In the first switching mechanism 250, the first cooling valve 251, the first heating valve 252, and the outdoor refrigerant return valve 253 may be opening/closing devices capable of regulating the opening degree from a fully closed state to a fully open state.
The first switching mechanism 250 corresponds to the "other switching mechanism" in the present disclosure.
On the pipe 240, the second switching mechanism 254 is provided on an opposite side of the first switching mechanism 250 with the outdoor heat exchanger 215 sandwiched therebetween. In other words, the second switching mechanism 254 is connected to the outdoor heat exchanger 215 through the pipe 240.
The second switching mechanism 254 connects the outdoor heat exchanger 215, the indoor heat exchanger 222, the refrigeration-facility heat exchanger 232, and the gas-liquid separator 216 to one another. The second switching mechanism 254 is a mechanism that switches the refrigerant to flow through any one of a plurality of flow paths that connect the outdoor heat exchanger 215, the indoor heat exchanger 222, the refrigeration-facility heat exchanger 232, and the gas-liquid separator 216 to one another.
The second switching mechanism 254 is formed in such a manner that end portions of first to fourth pipes 273, 274, 275, and 276 are connected at connection portions A, B, C, and D in a ring shape.
A throttling mechanism 255 is disposed in the first pipe 273. A refrigerant return expansion mechanism 258 is disposed in the second pipe 274 to control the flow rate.
A check valve 259 is disposed in the third pipe 275. A check valve 259 is disposed in the fourth pipe 276. In the present embodiment, the check valve 259 is a so-called self-acting automatic valve that is opened and closed by the flow of the refrigerant.
The throttling mechanism 255 and the refrigerant return expansion mechanism 258 are flow-rate control valves capable of changing the opening degree from a fully closed state to a fully open state. The throttling mechanism 255 can change the pressure of the refrigerant flowing through the first pipe 273 by regulating the opening degree. The refrigerant return expansion mechanism 258 can change the pressure of the refrigerant flowing through the second pipe 274 by regulating the opening degree. In other words, the throttling mechanism 255 and the refrigerant return expansion mechanism 258 are so-called throttle valves.
In the third pipe 275, the check valve 259 is disposed such that the refrigerant flows only toward the connection portion C from the connection portion B. In the fourth pipe 276, the check valve 259 is disposed such that the refrigerant flows only toward the connection portion D from the connection portion C.
Each of the throttling mechanism 255, the refrigerant return expansion mechanism 258, and the check valve 259 corresponds to a "valve body" in this disclosure.
The pipe 240, in which the outdoor heat exchanger 215 is provided, is connected to the connection portion A between the throttling mechanism 255 and the refrigerant return expansion mechanism 258.
The connection portion B between the refrigerant return expansion mechanism 258 and the check valve 259 provided in the third pipe 275 is connected to a middle part of the pipe 277 connecting the gas-liquid separator 216 and the refrigeration-facility heat exchanger 232. On the pipe 277, an inlet-side refrigeration-facility expansion mechanism 231 is provided between the point, where the connection portion B is connected, and the refrigeration-facility heat exchanger 232.
The connection portion C between the check valve 259 provided in the third pipe 275 and the check valve 259 provided in the fourth pipe 276 is connected to the indoor heat exchanger 222 through the pipe 278. In the pipe 278, an indoor expansion mechanism 221 of the indoor unit 220 is provided between one end to which the connection portion C is connected and the indoor heat exchanger 222. The indoor expansion mechanism 221 is an opening/closing device capable of changing the opening degree from a fully closed state to a fully open state. The indoor expansion mechanism 221 functions as a so-called throttle valve that can change the pressure of the refrigerant flowing through the pipe 278 by regulating the opening degree. Each of the indoor expansion mechanism 221 and the throttling mechanism 255 corresponds to a "throttling mechanism" in this disclosure.
The connection portion D between the check valve 259 provided in the fourth pipe 276 and the throttling mechanism 255 is connected to the gas-liquid separator 216 through the pipe 279.
As described above, the gas-liquid separator 216 is connected to the outdoor heat exchanger 215, the indoor heat exchanger 222, and the refrigeration-facility heat exchanger 232 through the second switching mechanism 254. Thus, when the refrigeration system 201 performs the first operation mode, the refrigerant flows into the gas-liquid separator 216 from the pipe 279, and flows out from the pipe 277. In other words, the pipe 279 functions as an inlet-side pipe of the gas-liquid separator 216, and the pipe 277 functions as an outlet-side pipe of the gas-liquid separator 216.
The second switching mechanism 254 corresponds to a "switching mechanism" in the present disclosure.
Next, the utilization-side heat exchanger provided in the refrigeration system 201 will be described.
When the indoor unit 220 performs a cooling operation, the indoor heat exchanger 222 functions as an evaporator. In the refrigeration system 201, the rotational frequency of each of the compressors and the air flow rate of blowers 218 and 228 are determined based on a temperature difference between the setting temperature of the indoor unit 220 and a temperature in the air-conditioned space in which the indoor unit 220 is installed. Furthermore, an opening degree of the indoor expansion mechanism 221 is determined such that the degree of superheat of the refrigerant at each of an inlet side and an outlet side of the indoor heat exchanger 222 becomes a specified value. Thus, the refrigeration system 201 operates such that the air-conditioned space becomes the setting temperature. In the present embodiment, an evaporation temperature zone of the indoor heat exchanger 222 is, for example, 3°C to 6°C.
The refrigeration-facility heat exchanger 232 functions as an evaporator. In the refrigeration system 201, the rotational frequency of each of the compressors and the air flow rate of blowers 218 and 238 are determined based on a temperature difference between the setting temperature of the refrigeration-facility unit 230 and a temperature of the interior of the showcase. Furthermore, an opening degree of the inlet-side refrigeration-facility expansion mechanism 231 is determined such that the degree of superheat of the refrigerant at each of an inlet side and an outlet side of the refrigeration-facility heat exchanger 232 becomes a specified value. Thus, the refrigeration system 201 operates such that the interior of the showcase becomes the setting temperature.
The refrigeration-facility unit 230 of the present embodiment can select and set, as an interior temperature zone, any one temperature zone from, for example, a refrigeration temperature zone (3°C to 6°C), a temperature zone (3°C to 8°C) slightly higher than the refrigeration temperature zone, a partial temperature zone (- 3°C to - 1°C), and a freezing temperature zone (- 20°C to - 18°C). For this reason, the evaporation temperature zone of the refrigeration-facility heat exchanger 232 is set lower than the interior temperature zone.
When the refrigeration-facility unit 230 is set to the refrigeration temperature zone, the evaporation temperature zone of the refrigeration-facility heat exchanger 232 is, for example, - 5°C to 0°C.
When the refrigeration-facility unit 230 is set to the partial temperature zone, the evaporation temperature zone of the refrigeration-facility heat exchanger 232 is, for example, - 12°C to - 8°C.
When the refrigeration-facility unit 230 is set to the freezing temperature zone, the evaporation temperature zone of the refrigeration-facility heat exchanger 232 is, for example, - 40°C to - 20°C.
In this way, the refrigeration system 201 is provided with two utilization-side heat exchangers with different evaporation temperature zones. Out of the two utilization-side heat exchangers with different evaporation temperature zones, the indoor heat exchanger 222 is connected to the inlet side of the high-stage compressor 212, and the refrigeration-facility heat exchanger 232 having a lower evaporation temperature zone than the indoor heat exchanger 222 is connected to the inlet side of the low-stage compressor 211.
The indoor heat exchanger 222 corresponds to a "first utilization-side heat exchanger" in the present disclosure, and the refrigeration-facility heat exchanger 232 corresponds to a "second utilization-side heat exchanger" in the present disclosure.
Next, the gas-liquid separator 216 will be described.
The gas-liquid separator 216 is a so-called flash tank that separates a gas-liquid two-phase refrigerant flown in into a gas refrigerant and a liquid refrigerant.
In the present embodiment, when the refrigeration system 201 performs a cooling operation, the refrigerant flowing from the outdoor heat exchanger 215 flows in the gas-liquid separator 216 through the second switching mechanism 254. During the cooling operation of the refrigeration system 201, the refrigerant flowing from the second switching mechanism 254 into the gas-liquid separator 216 is depressurized by the throttling mechanism 255.
When the refrigeration system 201 performs a heating operation, the refrigerant flowing from the indoor heat exchanger 222 flows in the gas-liquid separator 216 through the second switching mechanism 254. During the heating operation of the refrigeration system 201, the refrigerant flowing from the second switching mechanism 254 into the gas-liquid separator 216 is depressurized by the indoor expansion mechanism 221.
In this way, when the refrigeration system 201 performs the first operation mode, the refrigerant flows into the gas-liquid separator 216 through the second switching mechanism 254 in a state where the pressure is regulated by the throttling mechanism 255 or the indoor expansion mechanism 221. In other words, during the first operation mode, the refrigeration system 201 is provided with the second switching mechanism 254, and thus the pressure of the refrigerant flowing into the gas-liquid separator 216 can be regulated with a simple circuit configuration.
A gas refrigerant return pipe 260 is connected to the gas-liquid separator 216, and the gas refrigerant return pipe 260 is connected to the pipe 271 and then to the accumulator 213. A gas refrigerant flow-rate control valve 261 is connected to the gas refrigerant return pipe 260. The gas refrigerant flow-rate control valve 261 is an opening/closing device capable of changing the opening degree from a fully closed state to a fully open state. In the refrigeration system 201, flow rate of the gas refrigerant flowing through the gas refrigerant return pipe 260 is regulated by the opening degree of the gas refrigerant flow-rate control valve 261.
In the present embodiment, some of the gas refrigerant separated by the gas-liquid separator 216 are regulated in flow rate by the gas refrigerant flow-rate control valve 261, are sent to accumulator 213, and are returned to the suction side of the high-stage compressor 212.
In this way, in the gas-liquid separator 216, some of the gas refrigerant separated by the gas-liquid separator 216 are separated from the liquid refrigerant and flows out of the gas-liquid separator 216, whereby the liquid refrigerant is cooled to a saturation temperature corresponding to the pressure of the gas-liquid separator 216. In other words, the gas-liquid separator 216 in the refrigeration system 201 functions as a heat exchanger that cools the liquid refrigerant, and a refrigeration capacity of the refrigeration system 201 can be increased.
In addition, according to the refrigeration system 201, the opening degree of the gas refrigerant flow-rate control valve 261 is controlled, and the return amount of the gas refrigerant is regulated, whereby a pressure difference is generated between the front and the rear of the indoor expansion mechanism 221. In other words, it is possible to generate a differential pressure of the refrigerant between the inlet and the outlet of the indoor unit 220 in the refrigeration circuit 202 of the refrigeration system 201.
Thus, when the refrigeration system 201 performs the cooling operation in particular, the flow of the refrigerant is prevented from being stagnate. Then, in the indoor heat exchanger 222 of the refrigeration system 201 having a higher evaporation temperature of the refrigerant, it is possible to control the refrigerant flowing through the indoor heat exchanger 222 at a pressure value obtained by adding a specified pressure value to the pressure value serving as the evaporation temperature of the refrigerant.
An internal heat exchanger 264 is provided in a middle of each of the gas refrigerant return pipe 260 and the pipe 277. The internal heat exchanger 264 is a so-called economizer heat exchanger. The internal heat exchanger 264 is disposed, on the pipe 277, between the gas-liquid separator 216 and the connection portion B, and is disposed, on the gas refrigerant return pipe 260, between the gas refrigerant flow-rate control valve 261 and the accumulator 213.
The internal heat exchanger 264 houses the pipe 277 and the gas refrigerant return pipe 260 therein at the above-described position, and exchanges heat between the liquid refrigerant flowing through the pipe 277 and the gas refrigerant flowing through the gas refrigerant return pipe 260.
Therefore, in the refrigeration system 201, in the internal heat exchanger 264 the liquid refrigerant is cooled with the gas refrigerant. Then, the liquid refrigerant is more reliably brought into a supercooled state, and increases in the degree of supercooling. Thus, even when the temperature of the liquid refrigerant in the gas-liquid separator 216 does not drop to the saturation temperature in the gas-liquid separator 216, the liquid refrigerant is cooled in the internal heat exchanger 264, and thus the temperature thereof is reduced to the saturation temperature or lower. Then, the refrigeration system 201 can secure the degree of supercooling of the liquid refrigerant, and can improve the operating efficiency.
A connection pipe 266 is provided in the refrigeration circuit 202. The connection pipe 266 connects, on the pipe 277, between the internal heat exchanger 264 and the connection portion B, and connects, on the gas refrigerant return pipe 260, between the gas refrigerant flow-rate control valve 261 and the internal heat exchanger 264. Some of the liquid refrigerant, which is subjected to heat exchange with the gas refrigerant in the internal heat exchanger 264, flows through the connection pipe 266. The liquid refrigerant flowing through the connection pipe 266 is mixed with the gas refrigerant before the heat exchange with the liquid refrigerant in the internal heat exchanger 264.
In other words, the internal heat exchanger 264 exchanges heat between the liquid refrigerant and the mixed refrigerant of the liquid refrigerant, which is cooled by heat exchange with the gas refrigerant in the internal heat exchanger 264, and the gas refrigerant.
Thus, the internal heat exchanger 264 can increase the degree of supercooling of the liquid refrigerant. Therefore, the refrigeration system 201 can improve the operating efficiency.
A liquid refrigerant flow-rate control valve 265 is provided in the connection pipe 266. The liquid refrigerant flow-rate control valve 265 is an opening/closing device capable of changing the opening degree from a fully closed state to a fully open state. In the refrigeration system 201, the flow rate of the liquid refrigerant flowing through the connection pipe 266 is regulated by the opening degree of the liquid refrigerant flow-rate control valve 265.
Next, a service valve 290 will be described.
In the refrigeration system 201, a service valve 290 is provided in the pipe 272. On the pipe 272, the service valve 290 is provided between an outlet side of the refrigeration-facility heat exchanger 232 and the outlet-side refrigeration-facility pressure regulation mechanism 233. In the present embodiment, the service valve 290 is provided in the refrigeration-facility unit 230.
The service valve 290 includes three connection ports, for example, including pipe connection ports 292 and 294 and an external connection port 296. Each of the pipe connection ports 292 and 294 and the external connection port 296 is a valve body that can be opened and closed.
The pipe connection port 292 is connected to the pipe 272 located closer to the outlet-side refrigeration-facility pressure regulation mechanism 233. The pipe connection port 294 is connected to the pipe 272 located on the outlet side of the refrigeration-facility heat exchanger 232. In the present embodiment, the pipe connection ports 292 and 294 are normally opened.
The external connection port 296 is provided to allow the pipe 272 to be communicable with the outside, and is formed to allow connection of an external device. In the present embodiment, for example, a manifold gauge, a refrigerant recovery device 350, a vacuuming unit 352, and a refrigerant filling unit 354 are connected (see FIGS. 23 and 9). The external connection port 296 is closed when no external device is connected. The external connection port 296 may be manually opened and closed by a worker.
In the refrigeration system 201, since the service valve 290 is provided between the outlet side of the refrigeration-facility heat exchanger 232 and the outlet-side refrigeration-facility pressure regulation mechanism 233, connection ports for external devices can be provided without significantly changing the layout structure of the refrigeration circuit 202. In addition, since the service valve 290 is provided at a location close to the connection point between the outdoor unit 210 and the refrigeration-facility unit 230, the refrigeration system 201 can improve workability when the external device is connected to the refrigeration system 201.
The service valve 290 corresponds to a "connection port" in the present disclosure.

[3-1-2. Configuration related to Control of Refrigeration System]

FIG. 17 is a block diagram of the refrigeration system 201.
As shown in FIGS. 16 and 17, the refrigeration system 201 is provided with a plurality of refrigerant pressure sensors 280. The refrigerant pressure sensors 280 are provided at predetermined locations of the refrigeration circuit 202 including the outdoor unit 210, the indoor unit 220, and the refrigeration-facility unit 230. The refrigerant pressure sensors 280 detect the pressure of the refrigerant flowing through those locations.
As shown in FIG. 16, the refrigerant pressure sensor 280 is provided, on the pipe 277, between the gas-liquid separator 216 and the internal heat exchanger 264. The refrigerant pressure sensor 280 is provided, on the gas refrigerant return pipe 260, between the gas refrigerant flow-rate control valve 261 and the accumulator 213.
Furthermore, the refrigerant pressure sensor 280 is provided, on the pipe 271, between the connection point of the pipe 271 and the first heating pipe 241, and the indoor heat exchanger 222. Furthermore, the refrigerant pressure sensor 280 is provided, on the pipe 272, between the outlet-side refrigeration-facility pressure regulation mechanism 233 and the suction side of the low-stage compressor 211.
The refrigerant pressure sensor 280 is provided on the refrigerant pipe that connects the discharge side of the high-stage compressor 212 and the oil separator 214.
As shown in FIGS. 16 and 17, the refrigeration system 201 is provided with a plurality of refrigerant temperature sensors 282. The refrigerant temperature sensors 282 are provided at predetermined locations of the refrigeration circuit 202 including the outdoor unit 210, the indoor unit 220, and the refrigeration-facility unit 230. The refrigerant temperature sensors 282 detect the temperature of the refrigerant flowing through these locations.
As shown in FIG. 16, the refrigerant temperature sensors 282 are provided on the refrigerant pipe located on the suction side and the refrigerant pipe located on the discharge side in each of the high-stage compressors 212. In addition, the refrigerant temperature sensor 282 is provided, on the pipe 272 located on the suction side of the low-stage compressor 211, between the outlet-side refrigeration-facility pressure regulation mechanism 233 and the suction side of the low-stage compressor 211.
Furthermore, the refrigerant temperature sensors 282 are provided on the refrigerant pipes connected to the inlet side and the outlet side of each of the indoor heat exchanger 222 and the refrigeration-facility heat exchanger 232.
As shown in FIG. 17, the refrigeration system 201 includes a space temperature sensor 227. The space temperature sensor 227 is disposed in the air-conditioned space of the indoor unit 220, and detects the temperature of the air-conditioned space.
The refrigeration system 201 includes an interior temperature sensor 237. The interior temperature sensor 237 is disposed inside a refrigerating display showcase or a freezing display showcase provided in the refrigeration-facility unit 230, and detects the interior temperature.
The blowers 218, 228, and 238 are provided in the outdoor unit 210, the indoor unit 220, and the refrigeration-facility unit 230, respectively. The blowers 218, 228, and 238 flow air to the outdoor heat exchanger 215, the indoor heat exchanger 222, and the refrigeration-facility heat exchanger 232, respectively, and facilitate heat exchange between the refrigerant and the air flowing through each of the outdoor heat exchanger 215, the indoor heat exchanger 222, and the refrigeration-facility heat exchanger 232.
The outdoor unit 210 includes an outdoor-unit communication portion 306 that communicates with the indoor unit 220 through a control wiring. The outdoor-unit communication portion 306 is configured with communication hardware, for example, a connector and a communication circuit that conform to a predetermined communication standard.
The outdoor unit 210 includes a control device 300. An outdoor unit I/F 305 is configured with communication hardware, for example, a connector and a communication circuit that conform to a predetermined communication standard. The outdoor unit I/F 305 communicates with the low-stage compressor 211, the high-stage compressor 212, the blower 218, the refrigerant pressure sensor 280, the refrigerant temperature sensor 282, and the outdoor-unit communication portion 306. The outdoor unit I/F 305 communicates with the first cooling valve 251, the first heating valve 252, the outdoor refrigerant return valve 253, the throttling mechanism 255, the refrigerant return expansion mechanism 258, the on-off valve 223, the gas refrigerant flow-rate control valve 261, the liquid refrigerant flow-rate control valve 265, and the service valve 290.
Furthermore, the outdoor unit I/F 305 communicates with an indoor unit I/F 315, a space temperature sensor 227, and a refrigeration-facility unit I/F 325.
The outdoor unit 210 includes the control device 300. The control device 300 includes a control unit 301 and a storage unit 303.
The control unit 301 is a processor such as a CPU or an MPU that operates based on a program stored in advance in the storage unit 303. The control unit 301 may be configured with a single processor or may be configured with a plurality of processors. A DSP or the like may be used as the control unit 301. Furthermore, the control circuit such as an LSI, an ASIC, or an FPGA can be used as the control unit 301.
The control unit 301 is capable of receiving various signals from each of portions provided in the outdoor unit 210, the indoor unit 220, and the refrigeration-facility unit 230 through the outdoor unit I/F 305.
The control unit 301 is connected, through the outdoor unit I/F 305, to each portion of the outdoor unit 210, for example, the storage unit 303 or the low-stage compressor 211, the indoor unit 220, and the refrigeration-facility unit 230 in a wired or wireless manner, and controls each portion.
The control unit 301 reads the computer program stored in the storage unit 303 and operates according to the read computer program, thereby functioning as an operation control unit 301a and a determination unit 301b.
The operation control unit 301a controls various devices such as each of the low-stage compressor 211, the high-stage compressor 212, and the opening/closing device provided in the outdoor unit 210. In addition, the operation control unit 301a transmits control signals to the indoor unit 220 and the refrigeration-facility unit 230 through the outdoor unit I/F 305 to cooperatively operate the refrigeration system 201.
The operation control unit 301a can change the rotation speed of the compression mechanism provided in each of the compressors, and can also change the discharge pressure of the refrigerant.
The operation control unit 301a can regulate the opening degree of the gas refrigerant flow-rate control valve 261, the throttling mechanism 255, the indoor expansion mechanism 221, the inlet-side refrigeration-facility expansion mechanism 231, the outlet-side refrigeration-facility pressure regulation mechanism 233, and the refrigerant return expansion mechanism 258. The operation control unit 301a can switch the opening/closing devices provided in each of the first switching mechanism 250 and the second switching mechanism 254, and the on-off valve 223 to either an open state or a closed state.
The determination unit 301b compares detection values of the refrigerant pressure sensors 280 or detection values of the refrigerant temperature sensors 282 with data such as a reference temperature or a reference pressure value included in setting data 303a stored in the storage unit 303.
The operation control unit 301a controls each unit of the refrigeration system 201 based on the determination from the determination unit 301b.
The storage unit 303 includes a memory device such as a RAM or a ROM, a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. In addition, the storage unit 303 stores computer programs, databases, tables, and the like used for various operations of the refrigeration system 201. These computer programs may be installed in the storage unit 303 from a computer-readable portable recording medium using a known setup program, for example. The portable recording medium may be, for example, a semiconductor storage device including a CD-ROM, a DVD-ROM, a USB memory, or an SSD. The computer programs may be installed from a predetermined server, for example.
Furthermore, the storage unit 303 may include a volatile storage region and may form a work area for the control unit 301.
The storage unit 303 stores the setting data 303a. The setting data 303a includes data on the setting temperature of the indoor unit 220 and data on the setting temperature of the refrigeration-facility unit 230.
The setting data 303a includes data, for example, the rotation speed that is a specified value for each compressor and a reference pressure value that is a specified value indicating a differential pressure at a predetermined location in the refrigeration circuit 202.
The setting data 303a includes data related to the first operation mode. Specifically, the setting data 303a includes information on the opening/closing or the opening degree of each of the valve bodies provided in the refrigeration circuit 202 when the first operation mode is performed. The control unit 301 controls each of the units in the refrigeration circuit 202 according to the data related to the first operation mode. Thus, the refrigeration system 201 performs the first operation mode.
The setting data 303a includes a second operation mode. The second operation mode is an operation mode of the refrigeration system 201 that is performed in conjunction with the operation of an external device connected to the external connection port 296. The setting data 303a includes information on the opening/closing or the opening degree of each of the valve bodies provided in the refrigeration circuit 202 when the second operation mode is performed. The control unit 301 controls each of the units in the refrigeration circuit 202 according to the data related to the second operation mode. Thus, the refrigeration system 201 performs the second operation mode.
In the present embodiment, the setting data 303a includes, as the second operation mode, three operation modes of a refrigerant recovery/vacuuming mode, a refrigerant charging mode, and a regulation operation mode.
The outdoor unit I/F 305 includes communication hardware such as a communication interface circuit or a connector for the outdoor unit 210 to communicate with each device according to a predetermined communication protocol via a cable and the like. The outdoor unit I/F 305 sends data received from each device to the control device 300, and transmits data received from the control device 300 to each device.
The control device 300 includes an operation panel 332. Operating elements are provided on the operation panel 332. When the operating elements are operated, the control device 300 transmits a signal to the outdoor unit 210 to switch the operation mode of the refrigeration system 201 from the first operation mode to the second operation mode. In the present embodiment, according to the operation of the operation panel 332, the control device 300 switches to any one of three second operation modes of the refrigerant recovery/vacuuming mode, the refrigerant charging mode, and the regulation operation mode, and executes the switched mode.
The control device 300 is provided with a display panel 334. The display panel 334 performs a predetermined screen display according to the signal transmitted from the outdoor unit 210. In the present embodiment, the display panel 334 can display, for example, an operating status when the first operation mode or the second operation mode is executed, or the presence or absence of malfunction in each unit of the refrigeration system 201, and notify a worker of the operating status or the malfunction.
The control device 300 corresponds to a "control unit" in the present disclosure. The operation panel 332 corresponds to an "operation unit" in the present disclosure. The display panel 334 corresponds to a "display unit" in the present disclosure.
The indoor unit 220 includes an indoor-unit control device 310 and the indoor unit I/F 315. The indoor-unit control device 310 includes an indoor-unit control unit 311 and an indoor-unit storage unit 313.
Similarly to the control unit 301, the indoor-unit control unit 311 is a processor such as a CPU or an MPU. The indoor-unit control unit 311 operates according to a computer program stored in the indoor-unit storage unit 313 to control various devices such as the blower 228 mounted in the indoor unit 220. In addition, the indoor-unit control unit 311 receives signals output from various sensors such as the space temperature sensor 227 mounted in the indoor unit 220.
Similarly to the storage unit 303, the indoor-unit storage unit 313 includes a storage device such as a RAM or a ROM, and stores computer programs and the like used for various operations of the indoor unit 220.
The indoor unit I/F 315 includes communication hardware such as a communication interface circuit or a connector for the indoor unit 220 to communicate with each device. The indoor unit I/F 315 sends data received from the space temperature sensor 227 and each device to the indoor-unit control device 310, and transmits data received from the indoor-unit control device 310 to each device.
The refrigeration-facility unit 230 includes a refrigeration-facility-unit control device 320 and a refrigeration-facility unit I/F 325. The refrigeration-facility-unit control device 320 includes a refrigeration-facility-unit control unit 321 and a refrigeration-facility-unit storage unit 323.
Similarly to the control unit 301, the refrigeration-facility-unit control unit 321 is a processor such as a CPU or an MPU. The refrigeration-facility-unit control unit 321 operates according to a computer program stored in the refrigeration-facility-unit storage unit 323 to control various devices such as the blower 238 mounted in the refrigeration-facility unit 230. In addition, the refrigeration-facility-unit control unit 321 receives signals output from various sensors such as the interior temperature sensor 237 mounted in the refrigeration-facility unit 230.
Similarly to the storage unit 303, the refrigeration-facility-unit storage unit 323 includes a storage device such as a RAM or a ROM, and stores computer programs and the like used for various operations of the refrigeration-facility unit 230.
The refrigeration-facility unit I/F 325 includes communication hardware such as a communication interface circuit or a connector for the refrigeration-facility unit 230 to communicate with each device. The refrigeration-facility unit I/F 325 sends data received from the interior temperature sensor 237 and each device to the refrigeration-facility-unit control device 320, and transmits data received from the refrigeration-facility-unit control device 320 to each device.
The operation control unit 301a and the determination unit 301b may be provided not only in the control unit 301 but also in the indoor-unit control unit 311 or the refrigeration-facility-unit control unit 321. For example, the operation control unit 301a and the determination unit 301b may be provided in a processor provided in another location of the refrigeration system 201. For example, the operation control unit 301a and the determination unit 301b may be provided in a processor provided in a server device or the like provided outside the refrigeration system 201. Such a server device may be capable of controlling each unit of the refrigeration system 201 via a network constituted of, for example, a public line network, a dedicated line, other communication lines, and various communication facilities.

[3-2. Operation of Refrigeration System]

Next, an operation of the present embodiment will be described.

[3-2-1. Cooling Operation]

First, an operation of the refrigeration system 201 during a cooling operation will be described.
During the cooling operation, as shown in FIG. 16, the outdoor heat exchanger 215 is used as a gas cooler or a radiator, and the indoor heat exchanger 222 and the refrigeration-facility heat exchanger 232 are used as evaporators.
During the cooling operation, the control device 300 opens the first cooling valve 251 and closes the first heating valve 252 and the outdoor refrigerant return valve 253 in the first switching mechanism 250. In addition, the control device 300 opens the throttling mechanism 255 and closes the refrigerant return expansion mechanism 258 in the second switching mechanism 254.
In this state, the low-stage compressor 211 and each of the high-stage compressors 212 are driven, whereby the refrigerant compressed by the low-stage compressor 211 is sent to each of the high-stage compressors 212, further compressed by each of the high-stage compressor 212, and discharged toward the oil separator 214.
The refrigerant passing through the oil separator 214 is sent to the outdoor heat exchanger 215 through the first cooling valve 251 of the first switching mechanism 250, and exchanges heat with outside air in the outdoor heat exchanger 215.
The refrigerant after heat exchange is sent from the connection portion A of the second switching mechanism 254 through the throttling mechanism 255 to the gas-liquid separator 216. The liquid refrigerant separated in the gas-liquid separator 216 reaches the connection portion B of the second switching mechanism 254 after passing through the pipe 277 and being subjected to heat exchange with the gas refrigerant in the internal heat exchanger 264. One refrigerant branched at the connection portion B passes through the pipe 278 and is sent to the indoor heat exchanger 222 through the check valve 259 provided in the pipe 275 and the indoor expansion mechanism 221 of the indoor unit 220.
In the indoor heat exchanger 222, the refrigerant exchanges heat with the indoor air to cool the indoor air. The refrigerant subjected to heat exchange with the indoor air passes through the pipe 271, and is returned to the suction side of each of the high-stage compressors 212 through the on-off valve 223 and the accumulator 213.
The other refrigerant branched at the connection portion B is sent to the refrigeration-facility heat exchanger 232 through the inlet-side refrigeration-facility expansion mechanism 231 of the refrigeration-facility unit 230, and is subjected to heat exchange in the refrigeration-facility heat exchanger 232 to cool the refrigeration-facility unit 230. The refrigerant subjected to heat exchange in the refrigeration-facility heat exchanger 232 is returned to the low-stage compressor 211 through the outlet-side refrigeration-facility pressure regulation mechanism 233.
In the cooling operation of the above-described refrigeration system 201, the refrigerant discharged from the high-stage compressor 212 and radiating heat while maintaining the pressure at a high pressure in the outdoor heat exchanger 215 is reduced in pressure by the throttling mechanism 255 to become an intermediate pressure, and is sent to the gas-liquid separator 216.

[3-2-2. Heating Operation]

Next, an operation of the refrigeration system 201 during a heating operation will be described.
FIG. 18 is a circuit diagram of the refrigeration system 201 showing a heating operation. In FIG. 18, a flow of the refrigerant is indicated by arrows in the drawing, and the refrigerant pipes through which the refrigerant flows are indicated by thick lines.
In the refrigeration system 201, the heating operation is performed, using the indoor heat exchanger 222 as a gas cooler or a radiator and the refrigeration-facility heat exchanger 232 as an evaporator.
As shown in FIG. 18, during the heating operation, the control device 300 opens the first heating valve 252 and closes the first cooling valve 251 and the outdoor refrigerant return valve 253 in the first switching mechanism 250. In addition, the control device 300 closes the throttling mechanism 255 and the refrigerant return expansion mechanism 258 in the second switching mechanism 254.
In this state, the low-stage compressor 211 and each of the high-stage compressors 212 are driven, whereby the refrigerant compressed by the low-stage compressor 211 is sent to each of the high-stage compressors 212, further compressed by each of the high-stage compressor 212, and discharged toward the oil separator 214.
The refrigerant passing through the oil separator 214 is sent to the indoor heat exchanger 222 through the first heating valve 252 of the first switching mechanism 250, and exchanges heat with indoor air in the indoor heat exchanger 222 to heat the indoor air.
The refrigerant subjected to heat exchange in the indoor heat exchanger 222 passes through the indoor expansion mechanism 221, reaches the connection portion C of the second switching mechanism 254, and is sent to the gas-liquid separator 216 through the check valve 259 and the throttling mechanism 255 provided in the pipe 276. The refrigerant separated in the gas-liquid separator 216 passes through the pipe 277, reaches the connection portion B of the second switching mechanism 254, and is sent to the refrigeration-facility heat exchanger 232 through the inlet-side refrigeration-facility expansion mechanism 231. The refrigerant exchange heat in the refrigeration-facility heat exchanger 232, and cools the refrigeration-facility unit 230.
The refrigerant subjected to heat exchange in the refrigeration-facility heat exchanger 232 passes through the pipe 272 and is returned to the suction side of the low-stage compressor 211 through the outlet-side refrigeration-facility pressure regulation mechanism 233.
In the refrigeration system 201 of the present disclosure, during the heating operation, the indoor heat exchanger 222 functions as a gas cooler or a radiator, and the outdoor heat exchanger 215 is not used. In other words, the refrigeration system 201 can perform heat exchange in the refrigeration-facility heat exchanger 232 using the refrigerant whose heat is radiated in the indoor heat exchanger 222, and thus can be operated without using the outdoor heat exchanger 215.
In the refrigeration system 201 of the present disclosure, during the heating operation, since the liquid refrigerant flows only through the refrigeration-facility unit 230, the opening degree of the gas refrigerant flow-rate control valve 261 is smaller compared to during cooling operation.

[3-2-3. Heating operation when amount of heat exhausted from refrigeration-facility unit is insufficient]

Next, an operation will be described in a case where a heating operation is performed when the amount of heat exhausted from the refrigeration-facility unit 230 is insufficient.
FIG. 19 is a circuit diagram of the refrigeration system 201 showing a heating operation when the amount of heat exhausted from the refrigeration-facility unit 230 is insufficient.
As shown in FIG. 19, during a heating operation at full capacity, the control device 300 opens the first heating valve 252, the outdoor refrigerant return valve 253, and the refrigerant return expansion mechanism 258, and closes the first cooling valve 251 and the throttling mechanism 255.
In this state, the low-stage compressor 211 and each of the high-stage compressors 212 are driven, whereby the refrigerant compressed by the low-stage compressor 211 is sent to each of the high-stage compressors 212, further compressed by each of the high-stage compressor 212, and discharged toward the oil separator 214.
The refrigerant passing through the oil separator 214 is sent to the indoor heat exchanger 222 through the first heating valve 252, and exchanges heat with indoor air in the indoor heat exchanger 222 to heat the indoor air.
The refrigerant subjected to heat exchange in the indoor heat exchanger 222 is sent to the gas-liquid separator 216 through the check valve 259 provided in the pipe 276, and then sent to the refrigeration-facility heat exchanger 232 through the inlet-side refrigeration-facility expansion mechanism 231. The refrigerant, which is subjected to cool the refrigeration-facility unit 230, and is subjected to heat exchange in the refrigeration-facility heat exchanger 232 is regulated through the outlet-side refrigeration-facility pressure regulation mechanism 233 to have the same pressure as that of the refrigerant which is sent from the first outdoor return pipe 242, and is returned to the low-stage compressor 211. This is an operation when the outside air temperature is lower than the interior temperature of the refrigeration-facility unit 230.
On the other hand, some of the refrigerant from the gas-liquid separator 216 are sent to the outdoor heat exchanger 215 through the refrigerant return expansion mechanism 258, and are returned to the low-stage compressor 211 after heat exchange in the outdoor heat exchanger 215.
Thus, exhaust heat from the refrigeration-facility heat exchanger 232 and heat pumped up by the outdoor heat exchanger 215 can be used as heat for the indoor heat exchanger 222, thereby increasing the heating capacity when the amount of heat exhausted from the refrigeration-facility unit 230 is insufficient.
Conventionally, when the outside air temperature is lower than the interior temperature of the refrigeration-facility unit 230, it is necessary to lower the evaporation temperature of the refrigeration-facility unit 230 in order to pump heat from the outdoor heat exchanger 215. However, when the evaporation temperature of the refrigeration-facility unit 230 is lowered, there is a concern that the temperature will be lower than the setting temperature of the refrigeration-facility unit 230.
Therefore, according to the present embodiment, the opening degree of the outlet-side refrigeration-facility pressure regulation mechanism 233 is controlled, whereby it is possible to achieve the balance of the pressure with the refrigerant sent from the outdoor heat exchanger 215, and to prevent a drop in the evaporation temperature of the refrigeration-facility unit 230.

[3-2-4. Heating operation when large capacity is required in refrigeration-facility unit but heat quantity for heating is not required]

Next, an operation will be described in a case where a large capacity is required in the refrigeration-facility unit 230 but a heat quantity for heating is not required.
FIG. 20 is a circuit diagram of the refrigeration system 201 showing an operation when a large capacity is required in the refrigeration-facility unit 230 but a heat quantity for heating is not required.
As shown in FIG. 20, when a large capacity is required in the refrigeration-facility unit 230 but a heat quantity for heating is not required, the control device 300 opens the first cooling valve 251, the throttling mechanism 255, the first heating valve 252, and the check valve 259 provided in the pipe 276, and closes the refrigerant return valve and the check valve 259 provided in the pipe 275.
In this state, the low-stage compressor 211 and each of the high-stage compressors 212 are driven, whereby the refrigerant compressed by the low-stage compressor 211 is sent to each of the high-stage compressors 212, further compressed by each of the high-stage compressor 212, and discharged toward the oil separator 214.
The refrigerant passing through the oil separator 214 is sent to the outdoor heat exchanger 215 through the first cooling valve 251, and exchanges heat with outside air in the outdoor heat exchanger 215.
The refrigerant after heat exchange is sent to the gas-liquid separator 216 through the throttling mechanism 255.
The refrigerant passing through the oil separator 214 is sent to the indoor heat exchanger 222 through the first heating valve 252, exchanges heat with indoor air in the indoor heat exchanger 222 to heat the indoor air.
The refrigerant subjected to heat exchange in the indoor heat exchanger 222 interflows with the refrigerant sent from the outdoor heat exchanger 215 through the check valve 259 provided in the pipe 276, and is sent to the gas-liquid separator 216.
The refrigerant from the gas-liquid separator 216 is sent to the refrigeration-facility heat exchanger 232 through the inlet-side expansion mechanism for the refrigeration-facility unit 230. The refrigerant, which is subjected to cool the refrigeration-facility unit 230, and is subjected to heat exchange in the refrigeration-facility heat exchanger 232 is returned to the low-stage compressor 211 through the outlet-side refrigeration-facility pressure regulation mechanism 233.
On the other hand, some of the refrigerant from the gas-liquid separator 216 is sent to the outdoor heat exchanger 215 through the refrigerant return expansion mechanism 258, and is returned to the low-stage compressor 211 after being subjected to heat exchange in the outdoor heat exchanger 215.
Thus, during the heating operation, the exhaust heat from the refrigeration-facility unit 230 can be radiated by the outdoor heat exchanger 215 and the indoor heat exchanger 222, whereby the cooling capacity of the refrigeration-facility unit 230 can be increased, and frost adhering to the outdoor heat exchanger 215 can be removed.
In this way, when the refrigeration system 201 perform the heating operation, the use state of the outdoor heat exchanger 215 can be switched to any one of a state of not being used, a state of being used as an evaporator, and a state of being used as a condenser, depending on the load on the indoor unit 220 and the refrigeration-facility unit 230. Therefore, the refrigeration system 201 can perform a stable heating operation depending on the load on the indoor unit 220 and the refrigeration-facility unit 230.

[3-2-5. State of refrigerant in refrigeration circuit]

FIG. 21 is a p-h chart showing a state of the refrigerant in the refrigeration circuit 202. In FIG. 19, a vertical axis p represents a pressure (MPa), and a horizontal axis h represents enthalpy (kJ/kg).
Here, a refrigerant of the refrigeration system 201 during the cooling operation will be described.
On the suction side of the low-stage compressor 211, the state of the refrigerant is located at point P1 in FIG. 21. The refrigerant is a refrigerant evaporated in the refrigeration-facility heat exchanger 232, and a gas refrigerant at point P1. For the convenience of description, a pressure at point P1 is referred to as a low pressure.
When a low-pressure refrigerant is sucked into the low-stage compressor 211 and adiabatically compressed, the state of the refrigerant is located at point P2 in FIG. 21. Hereinafter, for the convenience of description, a pressure at point P2 is referred to as an intermediated pressure. In the present embodiment, a differential pressure between the low pressure and the intermediate pressure is, for example, 1.0 MPa.
Such a refrigerant is mixed with the refrigerant evaporated in the indoor heat exchanger 222 and the gas refrigerant flowing through the gas refrigerant return pipe 260. The mixed refrigerants are lowered in temperature while being maintained at an intermediate pressure, and becomes a state at point P3 in FIG. 21.
When the refrigerant in the state at point P3 is adiabatically compressed, such a refrigerant is in a state at point P4 in FIG. 21. Hereinafter, for the convenience of description, a pressure at point P4 is referred to as a high pressure.
When such a refrigerant is discharged from the high-stage compressor 212, the refrigerant radiates heat while being maintained at a high pressure in the outdoor heat exchanger 215. Therefore, the refrigerant is in a state at point P5 in FIG. 21.
The refrigerant in the state at point P5 is depressurized by the throttling mechanism 255, and is in a state at point P6 in FIG. 21. At point P6, the refrigerant has a pressure value higher than the intermediate pressure. Hereinafter, for the convenience of description, the pressure at point P2 is referred to as a medium pressure. In the present embodiment, a differential pressure between the intermediate pressure and the medium pressure and the intermediate pressure is, for example, 0.5 MPa.
As described above, even when the refrigeration system 201 performs either the cooling operation or the heating operation, the low-pressure liquid refrigerant depressurized by the throttling mechanism 255 or the indoor expansion mechanism 221 flows into the gas-liquid separator 216. Thus, when the refrigeration system 201 performs the first operation mode, the pressure of the refrigerant entering the gas-liquid separator 216 can be regulated.
The refrigerant in the state at point P6 is separated into a liquid refrigerant and a gas refrigerant by the gas-liquid separator 216. Out of these refrigerants, the gas refrigerant is discharged from the gas-liquid separator 216 through the gas refrigerant return pipe 260.
As the gas refrigerant is separated from discharged from the gas-liquid separator 216, the liquid refrigerant is cooled to a state at point P7 on a saturated liquid line, as shown in FIG. 21.
As described above, the gas refrigerant return pipe 260 is connected to the suction side of the high-stage compressor 212. In other words, the gas refrigerant is sucked by the high-stage compressor 212 and discharged from the gas-liquid separator 216. Thus, in the refrigeration system 201, the liquid refrigerant stored in the gas-liquid separator 216 is cooled to the state at point P7 on the saturated liquid line.
The refrigeration system 201 includes one low-stage compressor 211 and two high-stage compressors 212. In other words, in the refrigeration system 201, the capacity of the high-stage compressor 212 is larger than that of the low-stage compressor 211. The gas refrigerant is sucked by these high-stage compressors 212, and thus the refrigeration system 201 can cool the liquid refrigerant in the gas-liquid separator 216 to the state at point P7 on the saturated liquid line even when the outside air of the air-conditioned space or the refrigeration-facility unit 230 is high, for example, in summer.
In this way, the refrigeration system 201 can perform the first operation mode even when the ambient temperature of the utilization-side heat exchanger is high.
The liquid refrigerant exchanges heat with the gas refrigerant in the internal heat exchanger 264, and is in a state at point P8 in FIG. 21. At point P8, the liquid refrigerant is in a supercooled state. The gas refrigerant, which exchanges heat with the liquid refrigerant in the internal heat exchanger 264, is in a state at point P11 in FIG. 21.
The liquid refrigerant flowing out from the internal heat exchanger 264 branches off at the connection portion B and flows to the indoor unit 220 and the refrigeration-facility unit 230. The liquid refrigerant flowing to the indoor unit 220 is depressurized to an intermediate pressure by the indoor expansion mechanism 221, and is in a state at point P9 in FIG. 21. Thereafter, the liquid refrigerant flowing to the indoor unit 220 evaporates in the indoor heat exchanger 222, and is in the state at point P3 in FIG. 21. The refrigerant flows out from the indoor unit 220, and is sent to the suction side of the high-stage compressor 212. Similarly, the gas refrigerant flowing out from the internal heat exchanger 264 is also sent to the suction side of the high-stage compressor 212.
The liquid refrigerant flowing into the refrigeration-facility unit 230 is depressurized to an intermediate pressure by the inlet-side refrigeration-facility expansion mechanism 231, and is in a state at point P10 in FIG. 21. Thereafter, the liquid refrigerant flowing into the refrigeration-facility unit 230 evaporates in the refrigeration-facility heat exchanger 232, and is in the state at point P1 in FIG. 21. The refrigerant flows out from the refrigeration-facility unit 230 and is sent to the suction side of the low-stage compressor 211.
As shown in FIG. 21, the refrigeration system 201 of the present embodiment is a system including the refrigeration circuit 202 to perform a two-stage compression, two-stage expansion cycle.
As described above, in the refrigeration system 201, the opening degree of the gas refrigerant flow-rate control valve 261 is controlled, and the return amount of the gas refrigerant is regulated, whereby the inlet side of the indoor heat exchanger 222 becomes an intermediate pressure, and the outlet side of the indoor heat exchanger 222 becomes a middle pressure. In other words, it is possible to generate a differential pressure of the refrigerant between the inlet and the outlet of the indoor expansion mechanism 221 in the refrigeration circuit 202 of the refrigeration system 201.
Thus, in the indoor heat exchanger 222 of the refrigeration system 201 having a higher evaporation temperature of the refrigerant, it is possible to control the refrigerant flowing through the indoor heat exchanger 222 at a pressure value obtained by adding a specified pressure value to the pressure value serving as the evaporation temperature of the refrigerant.
Thus, in the refrigeration system 201, it is possible to improve efficiency of an air conditioning temperature zone using carbon dioxide (R744), a natural refrigerant with high environmental preservation characteristics, and to improve the efficiency of the entire refrigeration system.
As described above, the refrigeration system 201 can be stably perform the state change of the refrigerant shown in FIG. 21 by regulating the pressure of the refrigerant using the throttling mechanism 255, the indoor expansion mechanism 221, and the gas refrigerant flow-rate control valve 261, and regulating the temperature of the refrigerant using the gas-liquid separator 216. Therefore, the refrigeration system 201 can perform a stable operation by regulating the pressure and temperature of the refrigerant according to the load on the indoor unit 220 and the refrigeration-facility unit 230 caused by the outside air temperature or the like.
Furthermore, in the refrigeration system 201, the liquid refrigerant and the gas refrigerant separated in the gas-liquid separator 216 exchange heat with each other in the internal heat exchanger 264. Thus, the liquid refrigerant sent to the indoor unit 220 and the refrigeration-facility unit 230 is supercooled. For this reason, even when the temperature of the refrigerant fluctuates due to external heat radiation or heat capacity of the gas-liquid separator 216, or fluctuation in an operating load of the refrigeration system 201, the liquid refrigerant is prevented from rising to a temperature at which flash gas is generated, for example. Then, the refrigeration system 201 can stably evaporate the refrigerant in the indoor heat exchanger 222 and the refrigeration-facility heat exchanger 232.
Additionally, in the refrigeration system 201, some of the liquid refrigerant, which exchanges heat with the gas refrigerant in the internal heat exchanger 264, is mixed with the gas refrigerant before heat exchange with the liquid refrigerant, through the connection pipe 266. Thus, in the internal heat exchanger 264, the liquid refrigerant exchanges heat with the mixed refrigerant of the liquid refrigerant, which is cooled by heat exchange with the gas refrigerant in the internal heat exchanger 264, and the gas refrigerant. Therefore, the internal heat exchanger 264 can increase the degree of supercooling of the liquid refrigerant, and the refrigeration system 201 can improve the operating efficiency.

[3-2-6. Operation of refrigeration system during cooling operation]

FIG. 22 is a flowchart showing an operation of the refrigeration system 201.
Next, an operation related to pressure control of the refrigeration system 201 during the cooling operation will be described.
As shown in FIG. 22, the determination unit 301b acquires a detection value of the refrigerant pressure sensor 280 provided on the discharge side of the indoor heat exchanger 222 and a detection value of the refrigerant pressure sensor 280 provided on the discharge side of the refrigeration-facility heat exchanger 232. The determination unit 301b calculates a differential pressure between an intermediate pressure and a low pressure from these acquired detection values. The determination unit 301b compares the calculated value with data of a reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA201).
When the calculated value is greater than the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA201: YES), the determination unit 301b acquires a detection value of the refrigerant pressure sensor 280 provided in the pipe 277 through which the liquid refrigerant discharged from the gas-liquid separator 216 flows. The determination unit 301b calculates a differential pressure between the intermediate pressure and the medium pressure, from such a detection value and the detection value of the refrigerant pressure sensor 280 provided on the discharge side of the indoor heat exchanger 222. Then, the determination unit 301b compares the calculated value with the data of the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA202).
When the calculated value is greater than the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA202: YES), the operation control unit 301a drives each of the compressors and the blowers 218, 228, and 238 to become the setting temperature of the indoor unit 220 (step SA203).
In step SA201, when the calculated value of the differential pressure between the intermediate pressure and the low pressure is equal to or smaller than the reference pressure value in the setting data 303a stored in the storage unit 303 (step SA201: NO), the operation control unit 301a regulates the opening degree of the gas refrigerant flow-rate control valve 261 and the throttling mechanism 255 to increase the intermediate pressure (step SA204).
In the refrigeration system 201, the intermediate pressure increases when the opening degree of the throttling mechanism 255 increases or the opening degree of the gas refrigerant flow-rate control valve 261 decreases.
Thereafter, the determination unit 301b acquires the detection value of refrigerant pressure sensor 280 provided on the discharge side of the indoor heat exchanger 222 and the detection value of the refrigerant pressure sensor 280 provided on the discharge side of the refrigeration-facility heat exchanger 232. The determination unit 301b calculates the differential pressure between the intermediate pressure and the low pressure from these acquired detection values, and compares the calculated value and the data of the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA205).
When the calculated value of the differential pressure between the intermediate pressure and the low pressure is equal to or smaller than the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA205: NO), the operation control unit 301a performs step SA204 again.
When both the calculated values of the differential pressure between the intermediate pressure and the low pressure are greater than the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA201: YES), the determination unit 301b performs step SA202.
Thus, in the refrigeration system 201, a differential pressure of a predetermined value or more is generated at the low-stage compressor 211, and the suction side and the discharge side of each of the high-stage compressors 212. Therefore, in the refrigeration system 201, the occurrence of poor compression in the low-stage compressor 211 and each of the high-stage compressors 212 is prevented.
As described above, the refrigeration system 201 of the present embodiment is provided with the internal heat exchanger 264 that exchanges heat between the liquid refrigerant flowing from the gas-liquid separator 216 to the indoor heat exchanger 222 and the refrigeration-facility heat exchanger 232 and the gas refrigerant discharged from the gas-liquid separator 216. Furthermore, the gas refrigerant discharged from the gas-liquid separator 216 is mixed with some of the liquid refrigerant that exchanges heat with the gas refrigerant discharged from the gas-liquid separator 216 in the internal heat exchanger 264, through the connection pipe 266. Thus, in the refrigeration system 201, the liquid refrigerant becomes a lower temperature, leading in improving the refrigeration capacity of the indoor unit 220 through which the liquid refrigerant flows.
When the setting temperature of the indoor unit 220 is higher than the temperature of the liquid refrigerant by a predetermined value or greater, the refrigeration system 201 reduces the opening degree of the indoor expansion mechanism 221 to restrict the flow rate of the liquid refrigerant flowing to the indoor unit 220. Thus, in the refrigeration system 201, the medium pressure, which is the pressure of the refrigerant flowing out from the indoor heat exchanger 222, in other words, the refrigerant sucked into each of the high-stage compressor 212, decreases.
In step SA202, when the calculated value of the differential pressure between the intermediate pressure and the medium pressure is smaller than the reference pressure value involved in setting data 303a stored in the storage unit 303 (step SA202: NO), the operation control unit 301a reduces the rotational frequency of the high-stage compressor 212 (step SA206).
Next, the determination unit 301b determines whether the reduced rotational frequency of the high-stage compressor 212 is greater than a specified value involved in the setting data 303a stored in the storage unit 303 (step SA207).
When the rotational frequency is greater than the specified value (step SA207: YES), the determination unit 301b again acquires a detection value of the refrigerant pressure sensor 280 provided in the pipe 277 through which the liquid refrigerant discharged from the gas-liquid separator 216 flows. The determination unit 301b calculates a differential pressure between the intermediate pressure and the medium pressure, from the acquired detection value and the detection value of the refrigerant pressure sensor 280 provided on the discharge side of the indoor heat exchanger 222. The determination unit 301b compares the calculated value with the data of the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA208).
When the calculated value is greater than the reference pressure value involved in the setting data 303a stored in the storage unit 303 (step SA208: YES), the operation control unit 301a drives each of the compressors and the blowers 218, 228, and 238 to become the setting temperature of the indoor unit 220 (step SA203).
when the calculated value of the differential pressure between the intermediate pressure and the medium pressure is equal to or smaller than the reference pressure value involved in setting data 303a stored in the storage unit 303 (step SA208: NO), the operation control unit 301a again reduces the rotational frequency of the high-stage compressor 212 (step SA206).
In step SA207, when the rotational frequency of the high-stage compressor 212 is lower than the specified value (step SA207: YES), the operation control unit 301a reduces the opening degree of the liquid refrigerant flow-rate control valve 265 (step SA209). Thereafter, the operation control unit 301a drives each of the compressors and the blowers 218, 228, and 238 to become the setting temperature of the indoor unit 220 (step SA203).
As described above, the refrigeration system 201 can control the rotational frequency of the high-stage compressor 212 to maintain the differential pressure between the intermediate pressure and the low pressure at a predetermined value or less. Accordingly, the refrigeration system 201 can improve the refrigeration efficiency of the indoor unit 220 while preventing the input to the high-stage compressor 212. Therefore, the refrigeration system 201 can improve the efficiency of the cooling operation while saving energy.
When the rotational frequency becomes smaller than the specified value, the refrigeration system 201 reduces the opening degree of the liquid refrigerant flow-rate control valve 265. Thus, the refrigeration system 201 reduces the flow rate at which the liquid refrigerant subjected to heat exchange with the gas refrigerant discharged from the gas-liquid separator 216 in the internal heat exchanger 264 is mixed with the gas refrigerant discharged from the gas-liquid separator 216. Therefore, the flow rate of the liquid refrigerant sent to the indoor unit 220 is reduced, and the decrease in the medium pressure is prevented. Furthermore, the refrigeration system 201 prevents the driving of each of the high-stage compressors 212 from being stopped.
In the above-described cooling operation of the refrigeration system 201, the refrigerant discharged from the high-stage compressor 212 and radiating heat while maintaining its pressure at a high pressure in the outdoor heat exchanger 215 is depressurized to the medium pressure by the throttling mechanism 255, and is sent to the gas-liquid separator 216.
On the other hand, during the heating operation of the refrigeration system 201, the refrigerant discharged from the high-stage compressor 212 radiates heat while maintaining its pressure at a high pressure in the indoor heat exchanger 222. The refrigerant is depressurized to the medium pressure by the indoor expansion mechanism 221, and is sent to the gas-liquid separator 216.
In the heating operation of the refrigeration system 201 when the amount of heat exhausted from the refrigeration-facility unit 230 is insufficient, the refrigerant discharged from the high-stage compressor 212 and radiating heat while maintaining its pressure at a high pressure in the outdoor heat exchanger 215 is depressurized to the medium pressure by the throttling mechanism 255, and is sent to the gas-liquid separator 216. Similarly, the refrigerant discharged from the high-stage compressor 212 and radiating heat while maintaining its pressure at a high pressure in the indoor heat exchanger 222 is depressurized to the medium pressure by the indoor expansion mechanism 221, and is sent to the gas-liquid separator 216.
In the heating operation of the refrigeration system 201 when a large capacity is required in the refrigeration-facility unit 230 but a heat quantity for heating is not required, the refrigerant discharged from the high-stage compressor 212 and radiating heat while maintaining its pressure at a high pressure in the indoor heat exchanger 222 is depressurized to the medium pressure by the indoor expansion mechanism 221, and is sent to the gas-liquid separator 216. In addition, some of the liquid refrigerant flowing out from the gas-liquid separator 216 is depressurized to the low pressure from the medium pressure by the refrigerant return expansion mechanism 258, and is sent to the outdoor heat exchanger 215.
As described above, the refrigeration system 201 includes the first switching mechanism 250. Thus, the refrigeration system 201 can switch between the cooling operation and the heating operation. In addition, during the heating operation, the refrigeration system 201 includes the first switching mechanism 250, so that the outdoor heat exchanger 215 can be switched between a state of not being used as a condenser and a state of being used as a condenser depending on the surplus or deficiency of the heat quantity.
As described above, the refrigeration system 201 includes the second switching mechanism 254. Thus, in both cases where the indoor heat exchanger 222 functions as an evaporator and where the indoor heat exchanger 222 functions as a condenser, the refrigeration system 201 can send out the refrigerant, which is sent out from each of the high-stage compressors 212, to the heat exchanger functioning as an evaporator through the gas-liquid separator 216. Therefore, the refrigeration system 201 can increase the refrigeration capacity.
Specifically, when the indoor unit 220 performs the cooling operation, the refrigerant discharged from each of the high-stage compressors 212 flows into the gas-liquid separator 216 by the second switching mechanism 254, and then flows into the indoor heat exchanger 222 and the refrigeration-facility heat exchanger 232.
When the indoor unit 220 performs the heating operation, the refrigerant sent out from each of the high-stage compressors 212 flows into the gas-liquid separator 216 by the second switching mechanism 254, and then flows into the refrigeration-facility heat exchanger 232 or the outdoor heat exchanger 215 depending on the surplus or deficiency of the heat quantity for heating.
Furthermore, the refrigeration system 201 includes the first switching mechanism 250 and the second switching mechanism 254, and can switch, during the heating operation, the outdoor heat exchanger 215 among a state of not being used, a state of being used as a condenser, and a state of being used as a evaporator depending on the surplus or deficiency of the heat amount. Thus, during the heating operation, the refrigeration system 201 switches the state of the outdoor heat exchanger, so that cooling exhaust heat from the refrigeration-facility heat exchanger 232 can be used to adjust surplus or deficiency of the heat quantity for heating of the indoor unit 220.
In this way, the refrigeration system 201 includes the first switching mechanism 250 and the second switching mechanism 254, thereby capable of increasing the refrigeration capacity and adjusting the surplus or deficiency of the heat quantity for heating while preventing an increase in the number of valve bodies and opening/closing devices to be controlled. In other words, the refrigeration system 201 can increase the refrigeration capacity and adjust the surplus or deficiency of the heat quantity for heating using the refrigeration circuit 202 with a simple configuration.

[3-2-7. Operation related to refrigerant recovery]

FIG. 23 is a circuit diagram showing a refrigeration circuit 202 of the refrigeration system 201 during refrigerant recovery/vacuuming work.
Next, the operation related to refrigerant recovery will be described.
A shown in FIG. 23, when a worker performs refrigerant recovery/vacuuming work on the refrigeration system 201, first, a refrigerant recovery device 350 or a vacuuming unit 352 is connected to the external connection port 296 of the service valve 290 through the connection pipe 356. The external connection port 296 is released by the worker after the connection pipe 356 is connected.
Next, the worker operates the operation panel 332 to select the refrigerant recovery/vacuuming mode. Thus, a predetermined signal is transmitted to the control device 300 from the operation panel 332. Upon receiving the signal, the control unit 301 controls all of the opening/closing devices provided in the refrigeration system 201 to be fully open. When all of the opening/closing devices are fully open, the control device 300 display, on the display panel 334, a screen indicating that the refrigeration system 201 performs the refrigerant recovery/vacuuming mode. Thereafter, the worker drives the refrigerant recovery device 350 or the vacuuming unit 352 to recover the refrigerant in the refrigeration circuit 202.

[3-2-8. Operation related to refrigerant filling]

FIG. 24 is a circuit diagram showing a refrigeration circuit 202 of the refrigeration system 201 during refrigerant filling work.
Next, the operation related to refrigerant filling will be described.
As shown in FIG. 24, when a worker performs refrigerant filling work on the refrigeration system 201, first, a refrigerant filling unit 354 is connected to the external connection port 296 of the service valve 290 through the connection pipe 356. The external connection port 296 is released by the worker after the connection pipe 356 is connected.
Next, the worker operates the operation panel 332 to select the refrigerant filling mode. Thus, a predetermined signal is transmitted to the control device 300 from the operation panel 332. Upon receiving the signal, the control unit 301 controls each of the first cooling valve 251, the first heating valve 252, the outdoor refrigerant return valve 253, the on-off valve 223, the throttling mechanism 255, the refrigerant return expansion mechanism 258, the gas refrigerant flow-rate control valve 261, the liquid refrigerant flow-rate control valve 265, the indoor expansion mechanism 221, and the outlet-side refrigeration-facility pressure regulation mechanism 233 to be fully closed. Upon receiving the signal, the control unit 301 controls each of the check valves 259, which are provided in the pipes 275 and 276, and the inlet-side refrigeration-facility expansion mechanism 231 to be open. When such control of these opening/closing devices is completed, the control device 300 causes the display panel 334 to display a screen indicating that the refrigeration system 201 performs the refrigerant filling mode. Thereafter, the worker drives the refrigerant filling unit 354 to send out the refrigerant to the refrigeration circuit 202.
Thus, the refrigerant is stored in the refrigeration-facility heat exchanger 232 and the gas-liquid separator 216 in the refrigeration circuit 202.
FIG. 25 is a circuit diagram showing a refrigeration circuit 202 of the refrigeration system 201 during a regulation operation.
When the refrigeration system 201 performs a cooling operation after the refrigerant filling work, the external connection port 296 is closed by the worker as shown in FIG. 25.
Next, the worker operates the operation panel 332 to select the regulation operation mode. Thus, a predetermined signal is transmitted from the operation panel 332 to the control device 300. Upon receiving the signal, the control unit 301 controls each of the first heating valve 252, the outdoor refrigerant return valve 253, the refrigerant return expansion mechanism 258, the check valve 259 provided in the pipe 276, and the outlet-side refrigeration-facility pressure regulation mechanism 233 to be fully closed. Upon receiving the signal, the control unit 301 controls each of the first cooling valve 251, the on-off valve 223, the throttling mechanism 255, the check valve 259 provided in the pipe 276, the gas refrigerant flow-rate control valve 261, the liquid refrigerant flow-rate control valve 265, the indoor expansion mechanism 221, and the inlet-side refrigeration-facility expansion mechanism 231 to be fully open. When the control of these opening/closing devices is completed, the control device 300 causes the display panel 334 to display a screen indicating that the refrigeration system 201 performs the regulation operation mode. Thereafter, the worker drives each of the high-stage compressors 212 and the indoor unit 220 in a state of stopping the refrigeration-facility unit 230 and the low-stage compressor 211. Thus, the refrigerant is sent out to the outdoor heat exchanger 215 and the indoor heat exchanger 222 in the refrigeration circuit 202. In this case, the indoor expansion mechanism 221 opens such that the medium-pressure refrigerant flowing in from the gas-liquid separator 216 becomes a low-pressure refrigerant. Therefore, a high-pressure refrigerant, an intermediate-pressure refrigerant, and a medium-pressure refrigerant are generated in the refrigeration system 201.

[3-3. Effects]

As described above, according to the present embodiment, the refrigeration system 201 includes the refrigeration circuit 202 that connects the outdoor unit 210 including the plurality of compressors, the outdoor heat exchanger 215, and the gas-liquid separator 216, the indoor unit 220 including the indoor heat exchanger 222, and the refrigeration-facility unit 230 including the refrigeration-facility heat exchanger 232.
The plurality of compressors are configured by the low-stage compressor 211 and the high-stage compressor 212, the indoor heat exchanger 222 having a high refrigerant evaporation temperature is connected to the high-stage compressor 212, and the refrigeration-facility heat exchanger 232 having a low refrigerant evaporation temperature is connected to the low-stage compressor 211.
The refrigeration circuit 202 includes the second switching mechanism 254 that causes the refrigerant discharged from the high-stage compressor 212 and flowing through at least either of the outdoor heat exchanger 215 or the indoor heat exchanger 222 to flow into the gas-liquid separator 216. The throttling mechanism 255 is provided between the outdoor heat exchanger 215 and the gas-liquid separator 216 to regulate the pressure of the refrigerant, and the indoor expansion mechanism 221 is provided between the indoor heat exchanger 222 and the gas-liquid separator 216.
Thus, the refrigeration system 201 can be formed with the refrigeration circuit 202 with a simple configuration, and can send the refrigerant to the evaporator through the gas-liquid separator 216 in both the case of performing the cooling operation and the case of performing the heating operation. Therefore, the refrigeration system 201 can improve the refrigeration capacity with a simple circuit configuration.
As in the present embodiment, the second switching mechanism 254 includes the pipes 273 to 276 that connect the outdoor heat exchanger 215, the indoor heat exchanger 222, the refrigeration-facility heat exchanger 232, and the gas-liquid separator 216 to one another. Each of the pipes 273 to 276 may be provided with the throttling mechanism 255 that regulates the flow of the refrigerant, the refrigerant return expansion mechanism 258, and the check valve 259.
Thus, in the refrigeration system 201, the refrigerant subjected to heat exchange by the gas-liquid separator 216 can be sent to any one of the outdoor heat exchanger 215, the indoor heat exchanger 222, and the refrigeration-facility heat exchanger 232 depending on the operation of the indoor unit 220 and the refrigeration-facility unit 230. Therefore, the refrigeration system 201 can increase the refrigeration capacity of the indoor unit 220 and the refrigeration-facility unit 230.
As in the present embodiment, the second switching mechanism 254 may include the check valve 259 and the throttling mechanism 255, as valve bodies.
Thus, in the refrigeration system 201, the refrigerant subjected to heat exchange by the gas-liquid separator 216 can be sent to any one of the outdoor heat exchanger 215, the indoor heat exchanger 222, and the refrigeration-facility heat exchanger 232 depending on the operation of the indoor unit 220 and the refrigeration-facility unit 230. Therefore, the refrigeration system 201 can increase the refrigeration capacity of the indoor unit 220 and the refrigeration-facility unit 230.
As in the present embodiment, the first switching mechanism 250 may be a mechanism that switches among any one of a flow path in which the refrigerant discharged from the high-stage compressor 212 flows to the outdoor heat exchanger 215, a flow path in which the refrigerant discharged from the high-stage compressor 212 flows to the indoor heat exchanger 222, and a flow path in which the refrigerant discharged from the high-stage compressor 212 flows to both the outdoor heat exchanger 215 and the indoor heat exchanger 222.
Thus, the refrigeration system 201 can include the refrigeration circuit 202 with simpler configuration. In addition, the refrigeration system 201 can switch the operation without stopping the compressor.
As in the present embodiment, the first switching mechanism 250 may be provided with the first cooling valve 251 located between the discharge side of the high-stage compressor 212 and the outdoor heat exchanger 215 and the outdoor refrigerant return valve 253 located downstream of the first cooling valve 251 and between the discharge side of the high-stage compressor 212 and the suction side of the low-stage compressor 211.
Thus, the refrigeration system 201 can switch among any one of a flow path in which the refrigerant discharged from the high-stage compressor 212 flows to the outdoor heat exchanger 215, a flow path in which the refrigerant discharged from the high-stage compressor 212 flows to the indoor heat exchanger 222, a flow path in which the refrigerant discharged from the high-stage compressor 212 flows to both the outdoor heat exchanger 215 and the indoor heat exchanger 222. Therefore, the refrigeration system 201 can include the refrigeration circuit 202 with a simpler configuration.
As in the present embodiment, the refrigeration system 201 includes the control device 300 that controls each of the units of the refrigeration circuit 202. The control device 300 includes the operation panel 332 that can be operated by the worker. The control device 300 includes, as operation modes of the refrigeration circuit 202, the first operation mode in which the refrigerant flowing through the indoor heat exchanger 222 and the refrigeration-facility heat exchanger 232 is regulated at a predetermined temperature and the second operation mode in which the operation is performed according to the operation of the external device connected to the refrigeration circuit 202. The control device 300 may switch between the first operation mode and the second operation mode according to the operation on the operation panel 332.
Thus, the refrigeration system 201 can switch between the first operation mode and the second operation mode according to the operation on the operation panel 332. Therefore, in the refrigeration system 201, the worker can easily switch between the operation modes.
As in the present embodiment, the control device 300 may include a plurality of second operation modes, and may switch between the second operation modes according to the operation on the operation panel 332.
Thus, in the refrigeration system 201, the worker can perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling according to the operation on the operation panel 332. Therefore, in the refrigeration system 201, the worker can easily perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling.
As in the present embodiment, the control device 300 may include a display panel 334 that displays a status of the refrigeration circuit 202 in each of the operation modes.
Thus, in the refrigeration system 201, the worker can perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling according to the operation on the control device 300 while checking the status of the refrigeration system 201. Therefore, in the refrigeration system 201, the worker can easily perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling.
As in the present embodiment, the service valve 290, to which the external device can be connected, may be provided between the refrigeration-facility heat exchanger 232 and the suction side of the low-stage compressor 211.
Thus, in the refrigeration system 201, the service valve 290 is provided at a location close to the connection point between the outdoor unit 210 and the refrigeration-facility unit 230. Therefore, the refrigeration system 201 can improve workability when the external device is connected to the refrigeration system 201.

(Other Embodiments)

As described above, the third embodiment has been described as examples of techniques disclosed in the present application. However, the techniques of the present disclosure are not limited thereto, and are also applicable to embodiments where changes, replacements, additions, omissions, etc., are appropriately made. In addition, it is also possible to combine the components described in the first to third embodiments to create new embodiments.
Hereinafter, other embodiments will be described as examples.
The connection pipe 266 is provided in the refrigeration system 201 in the embodiments described above, but the 266 may not be provided.
In the above-described embodiments, the outlet-side refrigeration-facility pressure regulation mechanism 233 and the service valve 290 are provided in the refrigeration-facility unit 230. However, the present invention is not limited thereto, and the outlet-side refrigeration-facility pressure regulation mechanism 233 and the service valve 290 may be provided in the outdoor unit 210. For example, the outlet-side refrigeration-facility pressure regulation mechanism 233 and the service valve 290 may be provided in the pipe 272 between the outdoor unit 210 and the refrigeration-facility unit 230.
In the above-described embodiments, the refrigeration system 201 includes one indoor heat exchanger 222 and one refrigeration-facility heat exchanger 232. However, the present invention is not limited thereto, and the refrigeration system 201 may include another refrigeration-facility heat exchanger 232 instead of the indoor heat exchanger 222. In other words, the refrigeration system 201 may include a plurality of refrigeration-facility units 230 without including the indoor unit 220.
In this case, the plurality of refrigeration-facility heat exchangers 232 have different evaporation temperature zones. Out of the plurality of refrigeration-facility heat exchangers 232, the refrigeration-facility heat exchanger 232 having a higher evaporation temperature zone is connected to the inlet side of the high-stage compressor 212, and the refrigeration-facility heat exchanger 232 having a lower evaporation temperature zone is connected to the inlet side of the low-stage compressor 211.
For example, when the refrigeration system 201 includes the refrigeration-facility unit 230 set to the freezing temperature zone and the refrigeration-facility unit 230 set to the refrigeration temperature zone, the refrigeration-facility heat exchanger 232 in the refrigeration-facility unit 230 set to the refrigeration temperature zone is connected to the inlet side of the high-stage compressor 212. On the other hand, the refrigeration-facility heat exchanger 232 in the refrigeration-facility unit 230 set to the freezing temperature zone is connected to the inlet side of the low-stage compressor 211.
In the above-described embodiments, a plurality of utilization-side heat exchangers connected to the inlet side of the high-stage compressor 212 may be provided in parallel in the pipes 278 and 271. Similarly, a plurality of utilization-side heat exchangers connected to the inlet side of the low-stage compressor 211 may be provided in parallel in the pipes 277 and 272.
Furthermore, for example, a plurality of indoor heat exchangers 222 may be provided in parallel to each other in the pipes 278 and 271. In this case, the indoor expansion mechanism 221 may be provided on the inlet side of each of the indoor heat exchangers 222. In this case, the refrigeration system 201 includes a plurality of indoor units 220. In this case, one or a plurality of indoor heat exchanger 222 and one or a plurality of refrigeration-facility heat exchanger 232 may be provided in parallel in the pipes 278 and 271.
A plurality of refrigeration-facility heat exchangers 232 may be provided in parallel to each other in the pipes 277 and 272. In this case, an inlet-side refrigeration-facility expansion mechanism 231 may be provided on the inlet side of each of the refrigeration-facility heat exchangers 232. In this case, at least one of the refrigeration-facility heat exchangers 232 provided in parallel in the pipes 277 and 272 may have an evaporation temperature zone different from that of the other refrigeration-facility heat exchangers 232.
The control device 300 may include a touch panel having integrally the functions of the operation panel 332 and the display panel 334.
Furthermore, for example, the control device 300 may be provided in either the indoor unit 220 or the refrigeration-facility unit 230. For example, either the operation panel 332 or the display panel 334 may be provided integrally in any one of the outdoor unit 210, the indoor unit 220, and the refrigeration-facility unit 230.
Furthermore, for example, the control device 200 may be provided integrally in an operation terminal such as a remote control provided in the indoor unit 220 or the refrigeration-facility unit 230. The remote control is a terminal that controls setting temperature of the indoor unit 220 or the refrigeration-facility unit 230 or starts up the indoor unit 220 or the refrigeration-facility unit 230.
Furthermore, for example, the control device 300 may be a communication terminal such as a smartphone or a tablet in which apps or programs are installed to transmit a predetermined signal to the outdoor unit 210 or each unit of the refrigeration system 201. In this case, the control device 300 may be capable of communicating with the outdoor unit 210 and each unit of the refrigeration system 201 via a network constituted of a public line network, a dedicated line, other communication lines, and various communication facilities. Specific aspects of such a network are not limited. The communication network may include at least one of a wireless communication circuit and a wired communication circuit.
Furthermore, for example, the control device 300 may be a server device in which apps or programs are installed to transmit a predetermined signal to the outdoor unit 210 or each unit of the refrigeration system 201. The server device may be capable of communicating with the outdoor unit 210 and each unit of the refrigeration system 201 via the above-described network.
Each unit shown in FIG. 17 is an example and not particularly limited to a specific implementation. In other words, hardware individually corresponding to each component does not necessarily need to be implemented, and functions of each component may be achieved by one processor executing a computer program. Some functions achieved by software in the above-described embodiments may be achieved by hardware, or some functions achieved by hardware may be achieved by software. Specific detailed components of other units of the outdoor unit 210, the indoor unit 220, and the refrigeration-facility unit 230 are optionally changeable without departing from the spirit of the present invention.
Step units of the operation shown in FIG. 20 are divisions according to main processing contents to facilitate understanding of operation of each unit of the refrigeration system 201, and the operation is not limited by a division scheme of processing units and their names. The division into a larger number of step units may be made in accordance with processing contents. The division may be made such that one step unit includes a larger number of processes. Moreover, orders of steps may be interchanged as appropriate without interference with the spirit of the present invention.
Note that the above-described embodiments are intended to illustrate the technology of the present disclosure, and thus various modifications, substitutions, additions, omissions, and the like can be made within the claims or equivalents thereof.

(Supplementary Note)

The following techniques are disclosed according to the above-described embodiments.
(Technique 1) A refrigeration system including: a refrigeration cycle circuit that connects an outdoor unit including a compressor and an outdoor heat exchanger, an indoor unit including an indoor heat exchanger, and a refrigeration-facility unit including a refrigeration-facility heat exchanger; and a control unit, in which, the refrigeration cycle circuit includes a switching mechanism that switches a flow path of a refrigerant according to control of the control unit, and the control unit blocks an inflow of the refrigerant to the indoor heat exchanger during an outdoor defrosting operation for defrosting the outdoor heat exchanger, and operates the refrigeration cycle circuit using the refrigeration-facility heat exchanger as an evaporator and the outdoor heat exchanger as a gas cooler or a radiator.
According to the above-described configuration, the refrigeration system can operate the outdoor heat exchanger as a gas cooler or a radiator without flowing the refrigerant into the indoor heat exchanger. In addition, the heat amount can be concentrically used to raise the temperature of the outdoor heat exchanger, and the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently execute the defrosting operation of the outdoor heat exchanger while preventing a decrease in the heating capacity.
(Technique 2) The refrigeration system according to Technique 1, in which the refrigeration system further includes an interior temperature sensor that detects an interior temperature of the refrigeration-facility unit, and the control unit stops the inflow of the refrigerant to the refrigeration-facility heat exchanger before a start of the outdoor defrosting operation, and raises the interior temperature of the refrigeration-facility unit up to a first temperature that is higher than a setting value of the interior temperature.
According to the above-described configuration, in the refrigeration system, during the outdoor defrosting operation, the refrigerant evaporates at a high temperature using the refrigeration-facility heat exchanger of which temperature rises, whereby the temperature of the refrigerant supplied to the outdoor heat exchanger rises, and the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently execute the defrosting operation of the outdoor heat exchanger while preventing a decrease in the heating capacity.
(Technique 3) The refrigeration system according to Technique 2, in which the control unit executes, during the outdoor defrosting operation, a pull-down operation to lower the interior temperature from the first temperature to the setting value of the interior temperature.
According to the above-described configuration, the compressors are operated at a high rotation speed, and the high-temperature refrigerant is supplied to the outdoor heat exchanger, whereby the time for the outdoor defrosting operation can be shortened. Therefore, it is possible to efficiently execute the defrosting operation of the outdoor heat exchanger while preventing a decrease in the heating capacity.
(Technique 4) The refrigeration system according to any one of Techniques 1 to 3, in which the control unit operates the refrigeration cycle circuit after an end of the outdoor defrosting operation, using the indoor heat exchanger and the outdoor heat exchanger as a gas cooler or a radiator, and the refrigeration-facility heat exchanger as an evaporator.
According to the above-described configuration, it is possible to remove the defrost water adhering to the outdoor heat exchanger in parallel with the heating operation by the indoor unit. Therefore, it is possible to prevent refreezing of the defrost water in the outdoor heat exchanger while preventing a decrease in the heating capacity.
(Technique 5) The refrigeration system according to any one of Techniques 1 to 4, in which the control unit operates the refrigeration cycle circuit during a refrigeration-facility unit defrosting operation that performs defrosting of the refrigeration-facility heat exchanger, using the indoor heat exchanger as an evaporator, and the refrigeration-facility heat exchanger as a gas cooler or a radiator.
According to the above-described configuration, the refrigeration system can use the indoor heat exchanger as an evaporator to operate the refrigeration-facility heat exchanger as a gas cooler or a radiator. Therefore, it is possible to defrost the refrigeration-facility heat exchanger while preventing a decrease in the cooling capacity.
(Technique 6) A refrigeration system including a refrigeration cycle circuit that connects an outdoor unit including a compressor, an outdoor heat exchanger, an outdoor expansion mechanism, and an outdoor fan, an indoor unit including an indoor heat exchanger, an indoor expansion mechanism, and an indoor fan, and a refrigeration-facility unit including the refrigeration-facility heat exchanger and refrigeration-facility expansion mechanism, in which, a defrosting pipe is provided to connect a pipe between the refrigeration-facility heat exchanger and the compressor and a pipe between the indoor expansion mechanism and the outdoor expansion mechanism, and a defrosting on-off valve is provided in a middle of the defrosting pipe to be opened during a defrosting operation.
According to the above-described configuration, in the defrosting operation during the cooling operation, the relatively warm refrigerant sent from the outdoor heat exchanger can be used for defrosting of the refrigeration-facility heat exchanger, and the liquid return to the compressor can be prevented using the outdoor heat exchanger as an evaporator. On the other hand, in the defrosting operation during the heating operation, the relatively warm refrigerant sent from the indoor heat exchanger can be used for defrosting of the refrigeration-facility heat exchanger, and the liquid return to the compressor can be prevented using the indoor heat exchanger as an evaporator.
Therefore, an electric heater is no longer necessary unlike the related art, energy efficiency can be improved, and the reliability of the compressor can be improved by preventing the liquid return of the refrigerant.
(Technique 7) The refrigeration system according to Technique 6, in which during defrosting of the refrigeration-facility heat exchanger, an air flow rate by the outdoor fan or the indoor fan is changed depending on whether a heat amount required for defrosting of the refrigeration-facility heat exchanger is large or small, thereby adjusting a temperature of a refrigerant flowing into the refrigeration-facility heat exchanger.
According to the above-described configuration, the air flow rate by the outdoor fan or the indoor fan is changed, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
(Technique 8) The refrigeration system according to Technique 6, in which during defrosting of the refrigeration-facility heat exchanger, an amount of expansion of a refrigerant by any one of the outdoor expansion mechanism, the indoor expansion mechanism, and the refrigeration-facility expansion mechanism is changed depending on whether a heat amount required for defrosting is large or small, thereby adjusting a temperature of the refrigerant flowing into the refrigeration-facility heat exchanger.
According to the above-described configuration, the amount of expansion of the refrigerant by any one of the outdoor expansion mechanism, the indoor expansion mechanism, and the refrigeration-facility expansion mechanism is changed, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
(Technique 9) The refrigeration system according to Technique 6, in which a gas-liquid separator is provided between the outdoor heat exchanger, and the indoor heat exchanger and the refrigeration-facility heat exchanger, and during defrosting of the refrigeration-facility heat exchanger, a refrigerant flow path through which a refrigerant is directly sent from the outdoor heat exchanger to the refrigeration-facility heat exchanger and a refrigerant flow path through which the refrigerant is sent from the outdoor heat exchanger through the gas-liquid separator to the refrigeration-facility heat exchanger are switched depending on whether a heat amount required for defrosting is large or small, thereby adjusting a temperature of the refrigerant flowing into the refrigeration-facility heat exchanger.
According to the above-described configuration, when the heat amount required for defrosting is large, the refrigerant from the outdoor heat exchanger is circulated through the gas-liquid separator, whereby the refrigerant having a temperature according to the heat amount required for defrosting can be sent to the refrigeration-facility heat exchanger, and the cooling operation can be resumed using the refrigerant at a low temperature during the completion of defrosting.
(Technique 10) A refrigeration system including a refrigeration circuit including a plurality of compressors, a heat source-side heat exchanger, a plurality of utilization-side heat exchangers, and a gas-liquid separator, the plurality of compressors include a low-stage compressor, and a high-stage compressor, the plurality of utilization-side heat exchangers include a first utilization-side heat exchanger, and a second utilization-side heat exchanger having a refrigerant evaporation temperature lower than that of the first utilization-side heat exchanger, the refrigeration circuit is provided with a switching mechanism that causes a refrigerant, which is discharged from the high-stage compressor and flows through at least one of the heat source-side heat exchanger and the first utilization-side heat exchanger, to flow to the gas-liquid separator, and throttling mechanisms are provided between the heat source-side heat exchanger and the gas-liquid separator and between the first utilization-side heat exchanger and the gas-liquid separator to regulate a pressure of the refrigerant.
Thus, the refrigeration system can be formed with the refrigeration circuit with a simple configuration, and can send the refrigerant to the heat exchanger functioning as an evaporator through the gas-liquid separator in both the case of performing the cooling operation and the case of performing the heating operation. Therefore, the refrigeration system can improve the refrigeration capacity with a simple circuit configuration.
(Technique 11) The refrigeration system according to Technique 10, in which the switching mechanism includes pipes that connect the heat source-side heat exchanger, the first utilization-side heat exchanger, the second utilization-side heat exchanger, and the gas-liquid separator to one another, and a valve body is provided in each of the pipes to regulate a flow of the refrigerant.
Thus, in the refrigeration system, the refrigerant subjected to heat exchange by the gas-liquid separator can be sent to any one of the heat source-side heat exchanger, the first utilization-side heat exchanger, and the second utilization-side heat exchanger. Therefore, the refrigeration system can increase the refrigeration capacity.
(Technique 12) The refrigeration system according to Technique 11, in which the switching mechanism includes, as the valve body, a check valve, and the throttling mechanism.
Thus, in the refrigeration system, the refrigerant subjected to heat exchange by the gas-liquid separator can be sent to any one of the utilization-side heat exchanger, the first utilization-side heat exchanger, and the second utilization-side heat exchanger. Therefore, the refrigeration system can increase the refrigeration capacity.
(Technique 13) The refrigeration system according to any one of Techniques 10 to 12, in which the refrigeration circuit includes another switching mechanism that switches to any one of: a flow path in which the refrigerant discharged from the high-stage compressor flows to the heat source-side heat exchanger, a flow path in which the refrigerant discharged from the high-stage compressor flows to the first utilization-side heat exchanger, and a flow path in which the refrigerant discharged from the high-stage compressor flows to both the heat source-side heat exchanger and the first utilization-side heat exchanger.
Thus, the refrigeration system can include the refrigeration circuit with simpler configuration. In addition, the refrigeration system can switch the operation without stopping the compressor.
(Technique 14) The refrigeration system according to Technique 13, in which the another switching mechanism includes a first cooling valve that is a valve body located between a discharge side of the high-stage compressor and the heat source-side heat exchanger, and an outdoor refrigerant return valve that is a valve body located downstream of the first cooling valve and between the discharge side of the high-stage compressor and a suction side of the low-stage compressor.
Thus, the refrigeration system can switch between any one of a flow path in which the refrigerant discharged from the high-stage compressor flows to the heat source-side heat exchanger, a flow path in which the refrigerant discharged from the high-stage compressor flows to the first utilization-side heat exchanger, a flow path in which the refrigerant discharged from the high-stage compressor flows to both the outdoor heat exchanger and the first utilization-side heat exchanger. Therefore, the refrigeration system can include the refrigeration circuit with a simpler configuration.
(Technique 15) The refrigeration system according to any one of Techniques 10 to 14, in which the refrigeration system further includes a control unit that controls each component of the refrigeration circuit, the control unit includes an operation portion that can be operated by a worker, the control unit includes, as operation modes of the refrigeration circuit, a first operation mode in which a refrigerant flowing through the first utilization-side heat exchanger and the second utilization-side heat exchanger is regulated at a predetermined temperature, and a second operation mode in which an operation is performed according to an operation of an external device connected to the refrigeration circuit, and the control unit switches between the first operation mode and the second operation mode according to an operation on the operation portion.
Thus, the refrigeration system can switch between the first operation mode and the second operation mode according to the operation on the operation portion. Therefore, in the refrigeration system, the worker can easily switch between the operation modes.
(Technique 16) The refrigeration system according to Technique 15, in which the control unit includes a plurality of second operation modes, and switches between the second operation modes according to the operation on the operation portion.
Thus, in the refrigeration system, the worker can perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling according to the operation on the operation portion. Therefore, in the refrigeration system, the worker can easily perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling.
(Technique 17) The refrigeration system according to Technique 15 or 16, in which the control unit includes a display portion that displays a status of the refrigeration circuit in each of the operation modes.
Thus, in the refrigeration system, the worker can perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling according to the operation on the control unit while checking the status of the refrigeration system. Therefore, in the refrigeration system, the worker can easily perform the work related to the refrigerant recovery/vacuuming and the refrigerant filling.
(Technique 18) The refrigeration system according to any one of Techniques 10 to 17, in which a connection port is provided between the second utilization-side heat exchanger and a suction side of the low-stage compressor to be connectable to an external device.
Thus, the refrigeration system can improve workability when the external device is connected to the refrigeration system.

Industrial Applicability

The first aspect of the present disclosure is applicable to a refrigeration system. Specifically, the present disclosure is applicable to a commercial refrigeration system including an outdoor unit, an indoor unit, and a refrigeration-facility unit.
The refrigeration system according to the second aspect of the present disclosure can be suitably used as a refrigeration system in which defrosting of the refrigeration-facility unit is performed by flowing a warm refrigerant, thereby saving energy.
The refrigeration system according to the third aspect of the present disclosure can be suitably used as a refrigeration system capable of improving efficiency of an air conditioning temperature zone using a natural refrigerant, and improving the efficiency of the entire system.

Reference Signs List

1 refrigeration system
10 outdoor unit
11 low-stage compressor (compressor)
12 high-stage compressor (compressor)
13 accumulator
14 oil separator
15 outdoor heat exchanger
16 gas-liquid separator
17 outside air temperature sensor
18 outdoor fan
19 outdoor defrost detection sensor
20 indoor unit
21 indoor expansion mechanism
22 indoor heat exchanger
23 on-off valve
26 indoor refrigerant temperature sensor
27 blowout air temperature sensor
28 indoor fan
30 refrigeration-facility unit
31 refrigeration-facility heat exchanger
32 inlet-side refrigeration-facility expansion mechanism
33 outlet-side refrigeration-facility pressure adjustment mechanism
37 interior temperature sensor
38 refrigeration-facility fan
39 refrigeration-facility-unit defrost detection sensor
40 refrigerant pipe
41 first heating pipe
42 first outdoor return pipe
43 second cooling pipe
44 second heating pipe
45 second outdoor return pipe
50 first switching mechanism (switching mechanism)
51 first cooling valve
52 first heating valve
53 outdoor refrigerant return valve
54 second switching mechanism (switching mechanism)
55 second cooling valve
56 third cooling valve
57 second heating valve
58 refrigerant return expansion mechanism
59 check valve
60 gas refrigerant return pipe
61 gas refrigerant flow-rate control valve
70 refrigeration-facility-unit control device
71 refrigeration-facility-unit control unit
73 refrigeration-facility-unit storage unit
75 refrigeration-facility unit I/F
80 indoor-unit control device
81 indoor-unit control unit
83 indoor-unit storage unit
85 indoor unit I/F
90 control device
91 refrigeration-facility-unit control unit
91 control unit
91a determination unit
91b operation control unit
93 storage unit
93a setting data
95 outdoor unit I/F
L1 first outdoor defrost line
L2 second outdoor defrost line
101 refrigeration system
162 defrosting pipe
163 defrosting on-off valve
164 defrost sensor
170 control unit
201 refrigeration system
202 refrigeration circuit
210 outdoor unit
211 low-stage compressor
212 high-stage compressor
213 accumulator
214 oil separator
215 outdoor heat exchanger (heat source-side heat exchanger)
216 gas-liquid separator
218, 228, 238 blower
220 indoor unit
221 indoor expansion mechanism
222 indoor heat exchanger (first utilization-side heat exchanger)
223 on-off valve
227 space temperature sensor
230 refrigeration-facility unit
231 inlet-side refrigeration-facility expansion mechanism
232 refrigeration-facility heat exchanger (second utilization-side heat exchanger)
233 outlet-side refrigeration-facility pressure regulation mechanism
237 interior temperature sensor
240 pipe
241 first heating pipe
242 first outdoor return pipe
250 first switching mechanism (another switching mechanism)
251 first cooling valve
252 first heating valve
253 outdoor refrigerant return valve
254 second switching mechanism (switching mechanism)
255 throttling mechanism
258 refrigerant return expansion mechanism
259 check valve
260 gas refrigerant return pipe
261 gas refrigerant flow-rate control valve
264 internal heat exchanger
265 liquid refrigerant flow-rate control valve
266 connection pipe
271 pipe
272 pipe
273 first pipe
274 second pipe
275 third pipe
276 fourth pipe
277 pipe
278 pipe
279 pipe
280 refrigerant pressure sensor
282 refrigerant temperature sensor
290 service valve
292 pipe connection port
294 pipe connection port
296 external connection port
300 control device
301 control unit
301a operation control unit
301b determination unit
303 storage unit
303a setting data
305 outdoor unit I/F
306 outdoor-unit communication portion
310 indoor-unit control device
311 indoor-unit control unit
313 indoor-unit storage unit
315 indoor unit I/F
320 refrigeration-facility-unit control device
321 refrigeration-facility-unit control unit
323 refrigeration-facility-unit storage unit
325 refrigeration-facility unit I/F
332 operation panel
334 display panel
350 refrigerant recovery device
352 vacuuming unit
354 refrigerant filling unit
356 connection pipe
A, B, C, D connection portion

Claims

A refrigeration system comprising:
a refrigeration cycle circuit that connects an outdoor unit including a compressor and an outdoor heat exchanger, an indoor unit including an indoor heat exchanger, and a refrigeration-facility unit including a refrigeration-facility heat exchanger; and

a control unit, wherein

the refrigeration cycle circuit includes a switching mechanism that switches a flow path of a refrigerant according to control of the control unit, and

the control unit blocks an inflow of the refrigerant to the indoor heat exchanger during an outdoor defrosting operation for defrosting the outdoor heat exchanger, and operates the refrigeration cycle circuit using the refrigeration-facility heat exchanger as an evaporator and the outdoor heat exchanger as a gas cooler or a radiator.
The refrigeration system according to claim 1, further comprising an interior temperature sensor that detects an interior temperature of the refrigeration-facility unit, wherein
the control unit stops the inflow of the refrigerant to the refrigeration-facility heat exchanger before a start of the outdoor defrosting operation, and raises the interior temperature of the refrigeration-facility unit up to a first temperature that is higher than a setting value of the interior temperature.
The refrigeration system according to claim 2, wherein the control unit executes, during the outdoor defrosting operation, a pull-down operation to lower the interior temperature from the first temperature to the setting value of the interior temperature.
The refrigeration system according to claim 1, wherein the control unit operates the refrigeration cycle circuit after an end of the outdoor defrosting operation, using the indoor heat exchanger and the outdoor heat exchanger as a gas cooler or a radiator, and the refrigeration-facility heat exchanger as an evaporator.
The refrigeration system according to any one of claims 1 to 4, wherein the control unit operates the refrigeration cycle circuit during a refrigeration-facility unit defrosting operation that performs defrosting of the refrigeration-facility heat exchanger, using the indoor heat exchanger as an evaporator, and the refrigeration-facility heat exchanger as a gas cooler or a radiator.
A refrigeration system comprising
a refrigeration cycle circuit that connects an outdoor unit including a compressor, an outdoor heat exchanger, an outdoor expansion mechanism, and an outdoor fan, an indoor unit including an indoor heat exchanger, an indoor expansion mechanism, and an indoor fan, and a refrigeration-facility unit including a refrigeration-facility heat exchanger and a refrigeration-facility expansion mechanism, wherein

a defrosting pipe is provided to connect a pipe between the refrigeration-facility heat exchanger and the compressor and a pipe between the indoor expansion mechanism and the outdoor expansion mechanism, and a defrosting on-off valve is provided in a middle of the defrosting pipe to be opened during a defrosting operation.
The refrigeration system according to claim 6, wherein, during defrosting of the refrigeration-facility heat exchanger, an air flow rate by the outdoor fan or the indoor fan is changed depending on whether a heat amount required for defrosting of the refrigeration-facility heat exchanger is large or small, thereby adjusting a temperature of a refrigerant flowing into the refrigeration-facility heat exchanger.
The refrigeration system according to claim 6, wherein, during defrosting of the refrigeration-facility heat exchanger, an amount of expansion of a refrigerant by any one of the outdoor expansion mechanism, the indoor expansion mechanism, and the refrigeration-facility expansion mechanism is changed depending on whether a heat amount required for defrosting is large or small, thereby adjusting a temperature of the refrigerant flowing into the refrigeration-facility heat exchanger.
The refrigeration system according to claim 6, wherein a gas-liquid separator is provided between the outdoor heat exchanger, and the indoor heat exchanger and the refrigeration-facility heat exchanger, and
during defrosting of the refrigeration-facility heat exchanger, a refrigerant flow path through which a refrigerant is directly sent from the outdoor heat exchanger to the refrigeration-facility heat exchanger and a refrigerant flow path through which the refrigerant is sent from the outdoor heat exchanger through the gas-liquid separator to the refrigeration-facility heat exchanger are switched depending on whether a heat amount required for defrosting is large or small, thereby adjusting a temperature of the refrigerant flowing into the refrigeration-facility heat exchanger.
A refrigeration system comprising
a refrigeration circuit including

a plurality of compressors,

a heat source-side heat exchanger,

a plurality of utilization-side heat exchangers, and

a gas-liquid separator,

the plurality of compressors include

a low-stage compressor, and

a high-stage compressor,

the plurality of utilization-side heat exchangers include

a first utilization-side heat exchanger, and

a second utilization-side heat exchanger having a refrigerant evaporation temperature lower than that of the first utilization-side heat exchanger,

the refrigeration circuit is provided with a switching mechanism that causes a refrigerant, which is discharged from the high-stage compressor and flows through at least one of the heat source-side heat exchanger and the first utilization-side heat exchanger, to flow to the gas-liquid separator, and

throttling mechanisms are provided between the heat source-side heat exchanger and the gas-liquid separator and between the first utilization-side heat exchanger and the gas-liquid separator to regulate a pressure of the refrigerant.
The refrigeration system according to claim 10,
wherein the switching mechanism includes pipes that connect the heat source-side heat exchanger, the first utilization-side heat exchanger, the second utilization-side heat exchanger, and the gas-liquid separator to one another, and
a valve body is provided in each of the pipes to regulate a flow of the refrigerant.
The refrigeration system according to claim 11,
wherein the switching mechanism includes, as the valve body,
a check valve, and

the throttling mechanism.
The refrigeration system according to any one of claims 10 to 12, wherein the refrigeration circuit includes another switching mechanism that switches to any one of:
a flow path in which the refrigerant discharged from the high-stage compressor flows to the heat source-side heat exchanger,

a flow path in which the refrigerant discharged from the high-stage compressor flows to the first utilization-side heat exchanger, and

a flow path in which the refrigerant discharged from the high-stage compressor flows to both the heat source-side heat exchanger and the first utilization-side heat exchanger.
The refrigeration system according to claim 13,
wherein the another switching mechanism includes
a first cooling valve that is a valve body located between a discharge side of the high-stage compressor and the heat source-side heat exchanger, and

an outdoor refrigerant return valve that is a valve body located downstream of the first cooling valve and between the discharge side of the high-stage compressor and a suction side of the low-stage compressor.
The refrigeration system according to any one of claims 10 to 12, further comprising a control unit that controls each component of the refrigeration circuit,
wherein
the control unit includes an operation portion that can be operated by a worker,

the control unit includes, as operation modes of the refrigeration circuit,

a first operation mode in which a refrigerant flowing through the first utilization-side heat exchanger and the second utilization-side heat exchanger is regulated at a predetermined temperature, and

a second operation mode in which an operation is performed according to an operation of an external device connected to the refrigeration circuit, and

the control unit switch between the first operation mode and the second operation mode according to an operation on the operation portion.
The refrigeration system according to claim 15,
wherein the control unit includes a plurality of the second operation modes, and switches between the second operation modes according to an operation of the operation portion.
The refrigeration system according to claim 15,
wherein the control unit includes a display portion that displays a status of the refrigeration circuit in each of the operation modes.
The refrigeration system according to any one of claims 10 to 12, wherein a connection port is provided between the second utilization-side heat exchanger and a suction side of the low-stage compressor to be connectable to an external device.