WO2024079852A1 - Refrigeration cycle device - Google Patents

Abstract

A refrigerant circuit (1) includes a compressor (11), a four-way valve (12), a first heat exchanger (13), a first expansion valve (14), a second expansion valve (24), a second heat exchanger (25), and internal heat exchangers (15) and (16). The internal heat exchangers (15) and (16) exchange heat between a first flow path through which refrigerant flows between the first expansion valve (14) and the second expansion valve (24), and a second flow path through which the refrigerant flows between the four-way valve (12) and the compressor (11). The second flow path is configured such that the refrigerant branches, exchanges heat, and then merges. The number of branches in the second flow path is greater than the number of branches in the first flow path.

Description

Refrigeration Cycle Equipment

This disclosure relates to a refrigeration cycle device.

　Conventionally, a refrigeration cycle device is known that increases the efficiency of heat exchange by using an internal heat exchanger that exchanges heat between the refrigerant flowing through a first flow path and the refrigerant flowing through a second flow path in a refrigerant circuit.

The refrigeration cycle device of JP 2003-130483 A (Patent Document 1) uses one of the two internal heat exchangers during cooling operation and the other during heating operation by controlling the opening and closing of two solenoid valves. In this way, the refrigeration cycle device of JP 2003-130483 A (Patent Document 1) selectively uses one of the two internal heat exchangers during cooling operation and the other during heating operation.

JP 2003-130483 A

In light of refrigerant regulations, attempts are being made to switch to natural refrigerants such as R290. However, because R290 has the characteristic of having a low discharge temperature, in order to increase the efficiency of the refrigeration cycle equipment, it is necessary to raise the temperature of the refrigerant before it is sucked into the compressor. For this reason, it is considered to increase the length of the internal heat exchanger in the refrigeration cycle equipment, but increasing the length of the internal heat exchanger increases pressure loss and there is a risk of the coefficient of performance (COP) deteriorating.

Increasing the number of branches in the refrigerant flow path is one possible configuration to suppress the increase in pressure loss. However, simply increasing the number of branches will result in a decrease in the refrigerant velocity in the high-pressure refrigerant flow path, reducing the heat transfer performance in the internal heat exchanger.

The refrigeration cycle device in JP 2003-130483 A (Patent Document 1) has two internal heat exchangers that are used separately during cooling and heating operation, so although pressure loss does not increase, the efficiency of the refrigeration cycle device cannot be sufficiently improved.

The objective of this disclosure is to provide a refrigeration cycle device capable of highly efficient heat exchange in an internal heat exchanger.

The present disclosure relates to a refrigeration cycle device including a refrigerant circuit through which a refrigerant circulates. The refrigerant circuit includes a compressor, a flow path switching device that switches the flow path of the refrigerant, a first heat exchanger, a first expansion valve, a second expansion valve, a second heat exchanger, and an internal heat exchanger. The refrigerant circuit is configured such that during heating operation, the refrigerant flows in the following order: compressor, flow path switching device, first heat exchanger, first expansion valve, internal heat exchanger, second expansion valve, second heat exchanger, flow path switching device, internal heat exchanger, and compressor. The internal heat exchanger exchanges heat between a first flow path through which the refrigerant flows between the first expansion valve and the second expansion valve, and a second flow path through which the refrigerant flows between the flow path switching device and the compressor. The second flow path is configured such that the refrigerant branches and merges after heat exchange. The number of branches in the second flow path is greater than the number of branches in the first flow path.

The refrigeration cycle device disclosed herein has a second flow path between the four-way valve and the compressor, which has a greater number of branches than the first flow path and into which the flowing refrigerant branches and merges after heat exchange. According to the present disclosure, by branching the refrigerant, it is possible to prevent an increase in pressure loss, and by making the second flow path more branches than the first flow path, it is possible to prevent a decrease in the refrigerant speed in the first flow path, and heat exchange can be performed with high efficiency in the internal heat exchanger.

1 is a diagram showing a circuit configuration of a refrigeration cycle device in a first embodiment. This is a PH diagram for heating. This is a PH diagram for cooling. FIG. 13 is a diagram showing the temperature distribution of the internal heat exchanger in the case of heating. FIG. 13 is a diagram showing the temperature distribution of the internal heat exchanger in the case of cooling. 5 is a flowchart showing control of a compressor in the case of heating. 5 is a flowchart showing control of a first expansion valve in the case of heating. 10 is a flowchart showing control of a second expansion valve in the case of heating. 10 is a flowchart showing fan control in the case of heating. 5 is a flowchart showing control of a compressor in the case of cooling. 5 is a flowchart showing control of a second expansion valve in the case of cooling. 5 is a flowchart showing control of a first expansion valve in the case of cooling. 10 is a flowchart showing fan control in the case of cooling. FIG. 11 is a diagram showing a circuit configuration of a refrigeration cycle device in a second embodiment. FIG. 11 is a diagram showing a circuit configuration of a refrigeration cycle device in a third embodiment. FIG. 13 is a diagram showing a circuit configuration of a refrigeration cycle device in a fourth embodiment. FIG. 1 illustrates a multi-lobular tube configuration.

Below, the embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments described below, when numbers, quantities, etc. are mentioned, the scope of the present disclosure is not necessarily limited to those numbers, quantities, etc., unless otherwise specified. The same reference numbers will be used for the same parts or equivalent parts, and duplicate descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiments will be used in appropriate combinations.

Embodiment 1.
<Circuit configuration of refrigeration cycle device 10>
1 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 10 in a first embodiment. The refrigeration cycle apparatus 10 includes a refrigerant circuit 1 and a heat medium circuit 2. A refrigerant flowing through the refrigerant circuit 1 and a heat medium flowing through the heat medium circuit 2 are heat exchanged via a first heat exchanger 13. The refrigerant is, for example, a natural refrigerant such as R290. The heat medium is, for example, water, brine, or the like.

The refrigerant circuit 1 includes a compressor 11, a four-way valve 12, a first heat exchanger 13, a first expansion valve 14, internal heat exchangers 15 and 16 included in the internal heat exchanger IHX, a second expansion valve 24, a second heat exchanger 25, and a control device 100.

The compressor 11 draws in refrigerant and compresses it to a high-pressure, high-temperature state. The compressor 11 is configured to change its operating frequency according to a control signal received from the control device 100. Specifically, the compressor 11 incorporates a drive motor with a variable rotation speed that is inverter-controlled, and when the operating frequency is changed, the rotation speed of the drive motor changes. The output of the compressor 11 is adjusted by changing the operating frequency of the compressor 11. Various types of compressors 11 can be used, such as a rotary type, a reciprocating type, a scroll type, and a screw type.

The four-way valve 12 is controlled to be in either a heating operation state or a cooling operation state by a control signal received from the control device 100. In the heating operation state, the ports are connected as shown by the solid lines. In the cooling operation state, the ports are connected as shown by the dashed lines. By operating the compressor 11 in the heating operation state, the refrigerant circulates through the refrigerant circuit 1 in the direction shown by the solid arrow. By operating the compressor 11 in the cooling operation state, the refrigerant circulates through the refrigerant circuit 1 in the direction shown by the dashed arrow.

The first heat exchanger 13 exchanges heat between the refrigerant and the heat medium. The first heat exchanger 13 is a plate heat exchanger. As the first heat exchanger 13, a heat exchanger other than a plate heat exchanger, such as a shell-and-tube heat exchanger, may also be used.

The second heat exchanger 25 is an air-cooled heat exchanger that exchanges heat between the refrigerant and air supplied from a fan 26 as a blower. The second heat exchanger 25 evaporates and gasifies the refrigerant or condenses and liquefies the refrigerant by exchanging heat with the air. The first heat exchanger 13 and the second heat exchanger 25 may both be heat exchangers that exchange heat with a heat medium. The first heat exchanger 13 and the second heat exchanger 25 may both be air-cooled heat exchangers. The first heat exchanger 13 and the second heat exchanger 25 may be such that the first heat exchanger 13 is air-cooled and the second heat exchanger 25 exchanges heat with a heat medium.

The first expansion valve 14 and the second expansion valve 24 expand the refrigerant and reduce its pressure. The first expansion valve 14 and the second expansion valve 24 are, for example, electronic expansion valves (LEV: Linear Expansion Valves) whose opening can be controlled as desired.

The internal heat exchanger 15 includes flow paths 15a and 15b. In the case of heating, medium-pressure medium-temperature refrigerant that has passed through the first heat exchanger 13 functioning as a condenser and has been decompressed by the first expansion valve 14 flows through flow path 15a of the internal heat exchanger 15. In the case of heating, low-pressure low-temperature refrigerant that has passed through the second heat exchanger 25 functioning as an evaporator flows through flow path 15b of the internal heat exchanger 15. In the case of heating, the internal heat exchanger 15 exchanges heat between the medium-pressure medium-temperature refrigerant and the low-pressure low-temperature refrigerant. In the case of heating, the refrigerants flowing through flow paths 15a and 15b flow in opposite directions.

The internal heat exchanger 16 includes flow paths 16a and 16b. In the case of heating, the medium-pressure and medium-temperature refrigerant that has passed through flow path 15a flows through flow path 16a of the internal heat exchanger 16. In the case of heating, the low-pressure and low-temperature refrigerant that has passed through the second heat exchanger 25, which functions as an evaporator, flows through flow path 16b of the internal heat exchanger 16. In the case of heating, the internal heat exchanger 16 exchanges heat between the medium-pressure and medium-temperature refrigerant and the low-pressure and low-temperature refrigerant. In the case of heating, the refrigerants flowing through flow paths 16a and 16b are counterflows flowing in different directions. The internal heat exchangers 15 and 16 may be configured with solder tubes connecting two tubes, or with double tubes in which one tube is placed inside the other tube.

Next, the cooling operation will be described. In the cooling operation, medium-pressure and medium-temperature refrigerant that has passed through the second heat exchanger 25 functioning as a condenser and has been decompressed by the second expansion valve 24 flows through the flow path 16a of the internal heat exchanger 16. In the cooling operation, low-pressure and low-temperature refrigerant that has passed through the first heat exchanger 13 functioning as an evaporator flows through the flow path 16b of the internal heat exchanger 16. In the cooling operation, the internal heat exchanger 16 exchanges heat between the medium-pressure and medium-temperature refrigerant and the low-pressure and low-temperature refrigerant. In the cooling operation, the refrigerants flowing through the flow paths 16a and 16b are parallel flows flowing in the same direction.

In the case of cooling, medium-pressure, medium-temperature refrigerant that has passed through flow path 16a flows through flow path 15a of the internal heat exchanger 15. In the case of cooling, low-pressure, low-temperature refrigerant that has passed through the first heat exchanger 13, which functions as an evaporator, flows through flow path 15b of the internal heat exchanger 15. In the case of cooling, the internal heat exchanger 15 exchanges heat between the medium-pressure, medium-temperature refrigerant and the low-pressure, low-temperature refrigerant. In the case of cooling, the refrigerants flowing through flow paths 15a and 15b are parallel flows flowing in the same direction.

Here, the refrigerant flowing through the low-pressure side of the internal heat exchangers 15, 16 is a gas refrigerant with a high dryness, which has a low density and a high flow rate, resulting in a large pressure loss. On the other hand, the refrigerant flowing through the medium-pressure side of the internal heat exchangers 15, 16 is a refrigerant with a low dryness, which has a high density and a low flow rate, resulting in a small pressure loss. For this reason, when considering pressure loss, it is desirable to make the number of branches in the flow path of the refrigerant on the medium-pressure side smaller than the number of branches in the flow path of the refrigerant on the low-pressure side.

The refrigeration cycle device 10 further includes temperature sensors 111 to 116. The temperature sensor 111 is disposed on the discharge side of the compressor 11 and measures the temperature of the refrigerant discharged from the compressor 11. The temperature sensor 112 measures the temperature of the refrigerant flowing through the second heat exchanger 25. The temperature sensor 113 measures the temperature of the refrigerant flowing between the second expansion valve 24 and the second heat exchanger 25. The temperature sensor 114 measures the temperature of the refrigerant flowing between the first expansion valve 14 and the first heat exchanger 13. The temperature sensor 115 measures the temperature of the heat medium flowing through the heat medium circuit 2. The temperature sensor 116 measures the outside air temperature.

The refrigeration cycle device 10 further includes a pressure sensor 121. When the first heat exchanger 13 functions as a condenser, the pressure sensor 121 measures the pressure of the refrigerant discharged from the compressor 11.

The control device 100 is composed of a CPU (Central Processing Unit) 101, memory 102 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown), etc. The CPU 101 deploys a program stored in the ROM into the RAM etc. and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 100 are written. The control device 100 controls each device in the refrigeration cycle device 10 in accordance with these programs. This control is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuits).

The control device 100 controls the frequency of the compressor 11, the opening of the first expansion valve 14 and the second expansion valve 24, and the rotation speed of the fan 26 based on information from the various sensors described above. The control device 100 controls the four-way valve 12 to switch between heating and cooling operations.

The heat medium circuit 2 includes a radiator 31 and a pump 32. The radiator 31 exchanges heat between the indoor air and the heat medium. The pump 32 circulates the heat medium flowing through the heat medium circuit 2.

The flow of refrigerant during heating and cooling operations will be explained. During heating operation, the refrigerant circuit 1 is configured so that the refrigerant flows in the following order: compressor 11, four-way valve 12, first heat exchanger 13, first expansion valve 14, internal heat exchangers 15 and 16, second expansion valve 24, second heat exchanger 25, four-way valve 12, internal heat exchangers 16 and 15, and compressor 11.

During heating operation, the flow path through which the refrigerant flows from the first expansion valve 14 to the second expansion valve 24 is defined as the first flow path. The refrigerant passes through the first flow path, in which flow paths 15a and 16a are connected in series. During heating operation, the flow path through which the refrigerant flows from the four-way valve 12 to the compressor 11 is defined as the second flow path. The refrigerant passes through the second flow path, in which flow paths 16b and 15b are arranged in parallel. Here, the first flow path does not branch, and in this case the number of branches of the first flow path is set to 0. In contrast, the second flow path branches into two, so the number of branches is 2. In other words, the number of branches of the second flow path is greater than the number of branches of the first flow path.

During heating operation, the internal heat exchangers 15 and 16 exchange heat between the first flow path and the second flow path, which has more branches than the first flow path. The second flow path is configured so that the refrigerant branches and merges after heat exchange.

The refrigerant circuit 1 is configured so that during cooling operation, the refrigerant flows in the following order: compressor 11, four-way valve 12, second heat exchanger 25, second expansion valve 24, internal heat exchangers 16 and 15, first expansion valve 14, first heat exchanger 13, four-way valve 12, internal heat exchangers 16 and 15, and compressor 11.

During cooling operation, the flow path through which the refrigerant flows from the second expansion valve 24 to the first expansion valve 14 is defined as the first flow path. The refrigerant passes through the first flow path, in which flow path 16a and flow path 15a are connected in series. During cooling operation, the flow path through which the refrigerant flows from the four-way valve 12 to the compressor 11 is defined as the second flow path. The refrigerant passes through the second flow path, in which flow path 16b and flow path 15b are arranged in parallel. Here, the first flow path does not branch, and in this case the number of branches of the first flow path is set to 0. In contrast, the second flow path branches into two, so the number of branches is 2. In other words, the number of branches of the second flow path is greater than the number of branches of the first flow path.

During cooling operation, the internal heat exchangers 15, 16 exchange heat between the first flow path and the second flow path, which has more branches than the first flow path. The second flow path is configured so that the refrigerant branches and exchanges heat before merging. This allows for highly efficient heat exchange in the internal heat exchangers 15, 16, and reduces the pressure loss of the refrigerant passing through the low-pressure second flow path.

Next, we will explain how the ph diagram changes in the case of heating and cooling. Figure 2 is the ph diagram in the case of heating. Figure 3 is the ph diagram in the case of cooling.

As shown in FIG. 2, during heating operation, the high-pressure refrigerant is heat-exchanged with the heat medium by the first heat exchanger 13 from A1 to A2. The refrigerant is then depressurized by the first expansion valve 14 from A2 to A3 to become medium pressure. The refrigerant is then heat-exchanged with the low-pressure refrigerant by the internal heat exchangers 15 and 16 from A3 to A4. During heating operation, the refrigerant is supercooled as it passes through the internal heat exchangers 15 and 16. The refrigerant is then depressurized by the second expansion valve 24 from A4 to A5 to become low pressure. The refrigerant is then heat-exchanged with the air in the second heat exchanger 25 from A5 to A6, and is heat-exchanged with the medium-pressure refrigerant by the internal heat exchangers 15 and 16. The refrigerant is then compressed by the compressor 11 from A6 to A1 to become high pressure.

As shown in FIG. 3, during cooling operation, the high-pressure, high-temperature refrigerant exchanges heat with air from B1 to B2 by the second heat exchanger 25. The refrigerant is then depressurized by the second expansion valve 24 from B2 to B3 to medium pressure. The refrigerant then exchanges heat with the low-pressure refrigerant by the internal heat exchangers 15 and 16 from B3 to B4. During cooling operation, the refrigerant does not become supercooled when passing through the internal heat exchangers 15 and 16. The refrigerant is then depressurized by the first expansion valve 14 from B4 to B5 to low pressure. The refrigerant then exchanges heat with the heat medium by the first heat exchanger 13 from B5 to B6, and exchanges heat with the medium-pressure refrigerant by the internal heat exchangers 15 and 16. The refrigerant is then compressed by the compressor 11 from B6 to B1 to high pressure.

The internal volume of the first heat exchanger 13 is configured to be different from the internal volume of the second heat exchanger 25. Specifically, the internal volume of the first heat exchanger 13 is configured to be smaller than the internal volume of the second heat exchanger 25. Here, the value obtained by multiplying the internal volume by the density of the refrigerant is the amount of refrigerant that fills the heat exchanger. In the refrigerant circuit 1, the amount of refrigerant in the first heat exchanger 13 that functions as a condenser during heating operation is the reference for the total amount of refrigerant. In the refrigerant circuit 1, the internal volume of the first heat exchanger 13 that functions as a condenser during heating operation is smaller than the internal volume of the second heat exchanger 25 that functions as a condenser during cooling operation, so that the heating operation requires less refrigerant than the cooling operation. If the refrigerant amount is charged based on the cooling operation standard, the refrigerant amount will be excessive during heating operation, so it is necessary to install a refrigerant amount adjustment container such as a receiver or accumulator. On the other hand, in the refrigerant circuit 1 in which the refrigerant amount is determined based on the heating operation standard, the refrigerant amount will not be excessive during heating operation, so there is no need to install a refrigerant container such as a receiver.

The capacity of the first heat exchanger 13 may be configured to be greater than the capacity of the second heat exchanger 25. In this case, the refrigeration cycle device may use an air-cooled first heat exchanger 13 and a plate heat exchanger as the second heat exchanger 25.

Next, the temperature distribution of the refrigerant passing through the internal heat exchangers 15, 16 in the case of heating and cooling will be explained. Figure 4 is a diagram showing the temperature distribution of the internal heat exchangers 15, 16 in the case of heating. Figure 5 is a diagram showing the temperature distribution of the internal heat exchangers 15, 16 in the case of cooling. P1 to P7 shown in Figures 4 and 5 indicate the positions of the piping around the internal heat exchangers 15, 16 in the refrigerant circuit 1 of Figure 1.

As shown in FIG. 4, in the case of heating, the refrigerant on the medium pressure side passes through flow path 15a in a two-phase gas-liquid state from position P1 to position P2. At the same time, the refrigerant on the low pressure side passes through flow path 15b in a gas state from position P6 to position P7. In the case of heating, the refrigerant passing through flow path 15a and the refrigerant passing through flow path 15b flow in opposite directions and exchange heat. The refrigerant passing through flow path 15a is in a two-phase gas-liquid state and there is little change in temperature due to the latent heat that changes the state. The refrigerant passing through flow path 15b is in a gas state and the temperature rises from position P6 to position P7 due to the sensible heat that changes the temperature.

As shown in FIG. 4, in the case of heating, the refrigerant on the medium pressure side passes through flow path 16a in a liquid state from position P2 to position P3. At the same time, the refrigerant on the low pressure side passes through flow path 16b in a gaseous state from position P4 to position P5. In the case of heating, the refrigerant passing through flow path 16a and the refrigerant passing through flow path 16b flow in opposite directions and exchange heat. The refrigerant passing through flow path 16a is in a liquid state, and the temperature decreases from position P2 to position P3 due to sensible heat that changes the temperature. The refrigerant passing through flow path 16b is in a gaseous state, and the temperature increases from position P4 to position P5 due to sensible heat that changes the temperature.

As shown in FIG. 5, in the case of cooling, the refrigerant on the medium pressure side passes through flow path 16a in a two-phase gas-liquid state from position P3 to position P2. At the same time, the refrigerant on the low pressure side passes through flow path 16b in a gas state from position P4 to position P5. In the case of cooling, the refrigerant passing through flow path 16a and the refrigerant passing through flow path 16b flow in parallel and exchange heat. The refrigerant passing through flow path 16a is in a two-phase gas-liquid state and there is little change in temperature due to latent heat that changes the state. The refrigerant passing through flow path 16b is in a gas state and the temperature rises from position P4 to position P5 due to sensible heat that changes the temperature.

As shown in FIG. 5, in the case of cooling, the refrigerant on the medium pressure side passes through flow path 15a in a two-phase gas-liquid state from position P2 to position P1. At the same time, the refrigerant on the low pressure side passes through flow path 15b in a gas state from position P6 to position P7. In the case of cooling, the refrigerant passing through flow path 15a and the refrigerant passing through flow path 15b flow in parallel and exchange heat. The refrigerant passing through flow path 15a is in a two-phase gas-liquid state and there is little change in temperature due to latent heat that changes the state. The refrigerant passing through flow path 15b is in a gas state and the temperature rises from position P6 to position P7 due to sensible heat that changes the temperature.

In the case of heating, as shown in FIG. 4, the refrigerant flowing between flow paths 16a and 16b of the internal heat exchanger 16 flows in a counterflow manner and is supercooled to a liquid state. In other words, in the case of heating, the temperature is constant from position P1 to position P2, but the temperature drops from position P2 to position P3, so it is more efficient to have a larger temperature difference at position P3. For this reason, a counterflow flow in which the refrigerant inlet (position P4) exchanges heat with position P3 can ensure a larger temperature difference than a parallel flow in which the refrigerant outlet (position P5) exchanges heat with position P3. As a result, compared to the parallel flow, the temperature difference can be maintained between the low-pressure side and the medium-pressure side even if the state changes, and heat exchange can be performed with high efficiency.

In the case of cooling, as shown in FIG. 5, the refrigerant flowing in flow paths 16a and 15a of the internal heat exchanger 16 is in a gas-liquid two-phase state without being supercooled. The refrigerant flowing between flow paths 16a and 16b is in a parallel flow, and the refrigerant flowing between flow paths 15a and 15b is in a parallel flow. As a result, in the case of cooling, even if the medium pressure side is always in a gas-liquid two-phase state, the parallel flow ensures a temperature difference between the low pressure side and the medium pressure side, and the efficiency of the heat exchange does not decrease too much. In this way, parallel flow is necessary for cooling or heating, but parallel flow in the case of cooling, where supercooling does not occur, is more efficient than parallel flow in the case of heating, where supercooling occurs.

As shown in Figures 4 and 5, in the internal heat exchangers 15, 16 of the first embodiment, heat exchange can be performed while maintaining the temperature difference between the low-pressure side and the high-pressure side in both heating and cooling operations. This allows for highly efficient heat exchange in the internal heat exchangers 15, 16. Next, a description will be given of a flowchart when the control device 100 controls various devices. Figures 6 to 9 show the processing during heating operation. Figures 10 to 13 show the processing during cooling operation. The processing in Figures 6 to 13 is repeatedly called and executed as a subroutine from the main routine in the control of the control device 100.

FIG. 6 is a flowchart showing the control of the compressor 11 in the case of heating. First, in step S (hereinafter simply referred to as "S") 11, the control device 100 measures T115, which is the temperature of the heat medium obtained from the temperature sensor 115 arranged on the heat medium circuit 2 side of the first heat exchanger 13.

Then, the control device 100 determines whether T115 is higher than a preset target temperature (S12). If the control device 100 determines that T115 is higher than the target temperature (YES in S12), it reduces the frequency of the compressor 11 (S13) and returns the process from the subroutine to the main routine. If the control device 100 determines that T115 is lower than the target temperature (NO in S12), it increases the frequency of the compressor 11 (S14) and returns the process from the subroutine to the main routine.

The control device 100 can control the temperature on the heat medium circuit 2 side to reach the target temperature by the process shown in FIG. 6.

FIG. 7 is a flowchart showing the control of the first expansion valve 14 in the case of heating. First, in step S21, the control device 100 calculates the degree of subcooling (SC) from the refrigerant pressure obtained from the pressure sensor 121 located on the discharge side of the compressor 11 and the refrigerant temperature obtained from the temperature sensor 114 located at a position that detects the temperature of the refrigerant after passing through the first heat exchanger 13 (S21).

Specifically, the control device 100 acquires the pressure P of the refrigerant discharged from the compressor 11 from the pressure sensor 121, and calculates the saturation temperature of the refrigerant from the acquired pressure P. Furthermore, the control device 100 acquires the temperature T114 of the refrigerant that has passed through the first heat exchanger 13 from the temperature sensor 114. The control device 100 calculates the degree of subcooling (SC) of the refrigerant that has passed through the first heat exchanger 13 by subtracting the temperature T114 from the saturation temperature.

Then, the control device 100 determines whether the SC calculated in S21 is higher than a predetermined target SC (S22). If the control device 100 determines that the SC is higher than the target SC (YES in S22), it increases the opening of the first expansion valve 14 (S23), reduces the refrigerant pressure, and returns the process from the subroutine to the main routine. If the control device 100 determines that the SC is lower than the target SC (NO in S22), it decreases the opening of the first expansion valve 14 (S24), increases the refrigerant pressure, and returns the process from the subroutine to the main routine.

The control device 100 can adjust the refrigerant pressure by controlling the opening of the first expansion valve 14 so that the SC in the refrigerant circuit 1 becomes the target SC through the process shown in FIG. 7.

FIG. 8 is a flowchart showing the control of the second expansion valve 24 in the case of heating. First, in step S31, the control device 100 measures T111, which is the refrigerant temperature obtained from the temperature sensor 111 arranged on the discharge side of the compressor 11.

Then, the control device 100 determines whether T111 is higher than a preset target temperature (S32). If the control device 100 determines that T111 is higher than the target temperature (YES in S32), it increases the opening of the second expansion valve 24 (S33), reduces the refrigerant pressure, and returns the process from the subroutine to the main routine. If the control device 100 determines that T111 is lower than the target temperature (NO in S32), it decreases the opening of the second expansion valve 24 (S34), increases the refrigerant pressure, and returns the process from the subroutine to the main routine.

The control device 100 can control the temperature of the refrigerant discharged from the compressor 11 to a target temperature by the process shown in FIG. 8.

FIG. 9 is a flowchart showing the control of the fan 26 in the case of heating. First, in step S41, the control device 100 measures the outside air temperature T116 obtained from the temperature sensor 116. Next, the control device 100 determines the rotation speed of the fan 26 so that it becomes the rotation speed that is preset for each outside air temperature T116 (S42), and returns the process from the subroutine to the main routine.

The control device 100 can control the rotation speed of the fan 26 to change to a rotation speed that corresponds to the outside air temperature by the process shown in FIG. 9.

FIG. 10 is a flowchart showing the control of the compressor 11 in the case of cooling. First, in step S51, the control device 100 measures T115, which is the temperature of the heat medium obtained from the temperature sensor 115 arranged on the heat medium circuit 2 side of the first heat exchanger 13.

Then, the control device 100 determines whether T115 is lower than a preset target temperature (S52). If the control device 100 determines that T115 is lower than the target temperature (YES in S52), it decreases the frequency of the compressor 11 (S53) and returns the process from the subroutine to the main routine. If the control device 100 determines that T115 is higher than the target temperature (NO in S52), it increases the frequency of the compressor 11 (S54) and returns the process from the subroutine to the main routine.

The control device 100 can control the temperature on the heat medium circuit 2 side to reach the target temperature by the process shown in FIG. 10.

FIG. 11 is a flowchart showing the control of the second expansion valve 24 in the case of cooling. First, in step S61, the control device 100 calculates a value obtained by subtracting the refrigerant temperature T112 obtained from the temperature sensor 112 that detects the temperature of the refrigerant in the second heat exchanger 25 from the refrigerant temperature T113 obtained from the temperature sensor 113 that is positioned to detect the temperature of the refrigerant after passing through the second heat exchanger 25 (S61).

Then, the control device 100 determines whether the value of T113-T112 calculated in S61 is higher than a predetermined target value (S62). If the control device 100 determines that the value of T113-T112 is higher than the target value (YES in S62), it increases the opening of the second expansion valve 24 (S63), reduces the refrigerant pressure, and returns the process from the subroutine to the main routine. If the control device 100 determines that the value of T113-T112 is lower than the target value (NO in S62), it decreases the opening of the second expansion valve 24 (S64), increases the refrigerant pressure, and returns the process from the subroutine to the main routine.

By processing the data shown in FIG. 11, the control device 100 can adjust the refrigerant pressure by controlling the opening of the second expansion valve 24 so that the value of T113-T112 in the refrigerant circuit 1 becomes the target value.

FIG. 12 is a flowchart showing the control of the first expansion valve 14 in the case of cooling. First, in step S71, the control device 100 measures T111, which is the refrigerant temperature obtained from the temperature sensor 111 arranged on the discharge side of the compressor 11.

Then, the control device 100 determines whether T111 is higher than a preset target temperature (S72). If the control device 100 determines that T111 is higher than the target temperature (YES in S72), it increases the opening of the first expansion valve 14 (S73), reduces the refrigerant pressure, and returns the process from the subroutine to the main routine. If the control device 100 determines that T111 is lower than the target temperature (NO in S72), it decreases the opening of the first expansion valve 14 (S74), increases the refrigerant pressure, and returns the process from the subroutine to the main routine.

The control device 100 can control the temperature of the refrigerant discharged from the compressor 11 to a target temperature by the process shown in FIG. 12.

FIG. 13 is a flowchart showing the control of the fan 26 in cooling mode. First, in step S81, the control device 100 measures the outside air temperature T116 obtained from the temperature sensor 116. Next, the control device 100 determines the rotation speed of the fan 26 so that it is the rotation speed that is preset for each outside air temperature T116 (S82), and returns the process from the subroutine to the main routine.

The control device 100 can control the rotation speed of the fan 26 to change to a rotation speed that corresponds to the outside air temperature by the process shown in FIG. 13.

The control device 100 controls the various devices of the refrigeration cycle device 10 as shown in the processes of Figures 6 to 13. Specifically, during heating operation, the control device 100 controls the various devices of the refrigeration cycle device 10 so that the refrigerant on the inlet side of the internal heat exchangers 15, 16 is in a two-phase gas-liquid state and the refrigerant on the outlet side of the internal heat exchangers 15, 16 is in a liquid state. During cooling operation, the control device 100 controls the various devices of the refrigeration cycle device 10 so that the refrigerant on the inlet side and outlet side of the internal heat exchangers 15, 16 is in a two-phase gas-liquid state.

As a result, the control device 100 can maintain the temperature difference between the low-pressure side and the high-pressure side in both heating and cooling operations, as described in Figures 4 and 5, and perform heat exchange with high efficiency in the internal heat exchangers 15 and 16.

Embodiment 2.
<Circuit configuration of refrigeration cycle device 10A>
14 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 10A in embodiment 2. The refrigeration cycle apparatus 10A further includes internal heat exchangers 17 and 18 included in the internal heat exchanger IHX, as compared with the refrigeration cycle apparatus 10 in embodiment 1. In the refrigeration cycle apparatus 10A in embodiment 2, the configuration of the heat medium circuit 2 connected to the refrigerant circuit 1A is omitted. In embodiment 2, differences from embodiment 1 will be mainly described.

The internal heat exchanger 17 includes a flow path 17a and a flow path 17b. The internal heat exchanger 18 includes a flow path 18a and a flow path 18b.

During heating operation, the flow path through which the refrigerant flows from the first expansion valve 14 to the second expansion valve 24 is called the first flow path. The refrigerant passes through the first flow path, which is made up of flow paths 15a and 16a connected in series, and flow paths 17a and 18a connected in series. Flow paths 15a and 16a, and flow paths 17a and 18a are configured to branch into two paths in parallel.

During heating operation, the flow path from four-way valve 12 to compressor 11 is the second flow path. The refrigerant passes through the second flow path, in which flow paths 16b and 15b are arranged in parallel, and flow paths 18b and 17b are arranged in parallel. Flow paths 15b, 16b, 17b, and 18b are each configured to branch into four paths in parallel.

During cooling operation, the flow path through which the refrigerant flows from the second expansion valve 24 to the first expansion valve 14 is called the first flow path. The refrigerant passes through the first flow path, which connects flow paths 16a and 15a in series, and also connects flow paths 18a and 17a in series. Flow paths 16a and 15a, and flow paths 18a and 17a are configured to branch into two paths in parallel.

During cooling operation, the flow path from four-way valve 12 to compressor 11 is the second flow path. The refrigerant passes through the second flow path, in which flow paths 16b and 15b are arranged in parallel, and flow paths 18b and 17b are arranged in parallel. Flow paths 15b, 16b, 17b, and 18b are each configured to branch into four paths in parallel.

As shown in FIG. 14, the first flow path includes multiple auxiliary flow paths, ie, flow paths 15a and 16a, and flow paths 17a and 18a, which are branched into two. As shown in FIG. 14, the second flow path includes multiple auxiliary flow paths, ie, flow paths 15b, 16b, 17b, and 18b, which are branched into four in parallel. In this way, since the number of branches in the second flow path is greater than the number of branches in the first flow path, heat can be exchanged with high efficiency using the internal heat exchangers 15-18, and the pressure loss of the refrigerant passing through the low-pressure second flow path can be reduced.

Embodiment 3.
<Circuit configuration of refrigeration cycle device 10B>
15 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 10B in embodiment 3. The refrigeration cycle apparatus 10B further includes an internal heat exchanger 19 included in the internal heat exchanger IHX, as compared with the refrigeration cycle apparatus 10 in embodiment 1. In the refrigeration cycle apparatus 10B in embodiment 3, the configuration of the heat medium circuit 2 connected to the refrigerant circuit 1B is omitted. In embodiment 3, differences from embodiment 1 will be mainly described.

The internal heat exchanger 19 includes flow paths 19a and 19b. During heating operation, the flow path through which the refrigerant flows from the first expansion valve 14 to the second expansion valve 24 is defined as the first flow path. The refrigerant passes through the first flow path, which includes flow paths 15a, 16a, and 19a connected in series. During heating operation, the flow path through which the refrigerant flows from the four-way valve 12 to the compressor 11 is defined as the second flow path. The refrigerant passes through the second flow path, which includes flow paths 19b, 16b, and 15b arranged in parallel.

As shown in FIG. 15, flow path 15a, flow path 16a, and flow path 19a as multiple auxiliary flow paths included in the first flow path are configured to be connected in series. As shown in FIG. 15, flow path 19b, flow path 16b, and flow path 15b as multiple auxiliary flow paths included in the second flow path are branched into three in parallel. In this way, since the number of branches in the second flow path is greater than the number of branches in the first flow path, heat can be exchanged with high efficiency using internal heat exchangers 15, 16, and 19, and the pressure loss of the refrigerant passing through the low-pressure second flow path can be reduced.

Embodiment 4.
<Circuit configuration of refrigeration cycle device 10C>
Fig. 16 is a diagram showing a circuit configuration of a refrigeration cycle apparatus 10C in embodiment 4. The refrigeration cycle apparatus 10C is different from the refrigeration cycle apparatus 10 in embodiment 1 in that a multi-leaf tube 20 is used as an internal heat exchanger IHX instead of the internal heat exchangers 15 and 16. The multi-leaf tube 20 functions as an internal heat exchanger. In the refrigeration cycle apparatus 10C in embodiment 4, the configuration of the heat medium circuit 2 connected to the refrigerant circuit 1C is omitted. In embodiment 4, differences from embodiment 1 will be mainly described.

The configuration of the multi-leaf pipe 20 will be described. Figure 17 is a diagram showing the configuration of the multi-leaf pipe 20. A multi-leaf pipe 20 is a double pipe with the inside of the pipe made into a multi-leaf shape. For example, the multi-leaf pipe 20 includes a first flow path through which the medium-pressure refrigerant flows and a second flow path through which the low-pressure refrigerant flows. As shown in Figure 17, the first flow path includes flow paths 20A, 20B, 20C, and 20D. The second flow path includes flow paths 20a, 20b, 20c, 20d, and 20e.

During heating operation, the refrigerant flows from the first expansion valve 14 to the second expansion valve 24 through the first flow path of the multileaf tube 20, which is divided into four parallel flow paths 20A, 20B, 20C, and 20D. During heating operation, the refrigerant flows from the four-way valve 12 to the compressor 11 through the second flow path of the multileaf tube 20, which is divided into five parallel flow paths 20a, 20b, 20c, 20d, and 20e.

During cooling operation, the refrigerant flows from the second expansion valve 24 to the first expansion valve 14 through the first flow path of the multileaf tube 20, which is divided into four parallel flow paths 20A, 20B, 20C, and 20D. During cooling operation, the refrigerant flows from the four-way valve 12 to the compressor 11 through the second flow path of the multileaf tube 20, which is divided into five parallel flow paths 20a, 20b, 20c, 20d, and 20e.

As shown in FIG. 16, the flow paths 20A, 20B, 20C, and 20D as the multiple auxiliary flow paths included in the first flow path are branched into four paths in parallel. As shown in FIG. 16, the flow paths 20a, 20b, 20c, 20d, and 20e as the multiple auxiliary flow paths included in the second flow path are branched into five paths in parallel. In this way, since the number of branches in the second flow path is greater than the number of branches in the first flow path, heat exchange can be performed with high efficiency using the multi-leaf tube 20, and the pressure loss of the refrigerant passing through the low-pressure second flow path can be reduced.

<Summary>
The present disclosure relates to a refrigeration cycle device 10 including a refrigerant circuit 1 through which a refrigerant circulates. The refrigerant circuit 1 includes a compressor 11, a four-way valve 12 as a flow path switching device for switching a flow path of the refrigerant, a first heat exchanger 13, a first expansion valve 14, a second expansion valve 24, a second heat exchanger 25, and internal heat exchangers 15 and 16. The refrigerant circuit 1 is configured such that, during heating operation, the refrigerant flows through the compressor 11, the four-way valve 12, the first heat exchanger 13, the first expansion valve 14, the internal heat exchangers 15 and 16, the second expansion valve 24, the second heat exchanger 25, the four-way valve 12, the internal heat exchangers 15 and 16, and the compressor 11 in that order. The internal heat exchangers 15 and 16 exchange heat between a first flow path through which the refrigerant flows between the first expansion valve 14 and the second expansion valve 24 and a second flow path through which the refrigerant flows between the four-way valve 12 and the compressor 11. The second flow path is configured such that the refrigerant branches and merges after heat exchange. The number of branches in the second flow path is greater than the number of branches in the first flow path.

Preferably, the refrigerant circuit 1 is configured such that, by switching the four-way valve 12, the flow direction of the refrigerant is reversed in the first flow path, but the flow direction of the refrigerant is not reversed in the second flow path. During heating operation, the refrigerant flowing in the first flow path flows countercurrent to the refrigerant flowing in the second flow path. During cooling operation, the refrigerant flowing in the first flow path flows parallel to the refrigerant flowing in the second flow path.

Preferably, the capacity of the first heat exchanger 13 is different from the capacity of the second heat exchanger 25 .
Preferably, the capacity of the first heat exchanger 13 is smaller than the capacity of the second heat exchanger 25 .

Preferably, the system further includes a control device 100 for controlling the refrigerant circuit 1. The four-way valve 12 switches the flow path so that the refrigerant flows differently during heating operation and cooling operation. During heating operation, the control device 100 controls the frequency of the compressor 11, the opening of the first expansion valve 14, and the opening of the second expansion valve 24 so that the refrigerant state on the inlet side of the internal heat exchangers 15, 16 in the first flow path is a gas-liquid two-phase state, and the refrigerant state on the outlet side of the internal heat exchangers 15, 16 is a liquid state.

Preferably, during cooling operation, the control device 100 controls the frequency of the compressor 11, the opening of the first expansion valve 14, and the opening of the second expansion valve 24 so that the state of the refrigerant on the inlet and outlet sides of the internal heat exchangers 15, 16 in the first flow path is a gas-liquid two-phase state.

Preferably, the first flow path includes a plurality of first auxiliary flow paths, and the second flow path includes a plurality of second auxiliary flow paths. The first flow path is configured so that the plurality of first auxiliary flow paths are connected in series. The second flow path is configured so that the plurality of second auxiliary flow paths are arranged in parallel, with two or more branches.

Preferably, the first flow path includes a plurality of first auxiliary flow paths, and the second flow path includes a plurality of second auxiliary flow paths. The first flow path is configured such that the plurality of first auxiliary flow paths are arranged in parallel, with two or more branches. The second flow path is configured such that the plurality of second auxiliary flow paths are arranged in parallel, with the number of branches being greater than the number of first auxiliary flow paths in the first flow path.

The refrigeration cycle devices 10, 10A, 10B, and 10C of this embodiment have a greater number of branches than the first flow path, and a second flow path into which the flowing refrigerant branches, exchanges heat, and then merges is provided between the four-way valve 12 and the compressor 11. According to the present disclosure, by branching the refrigerant, it is possible to prevent an increase in pressure loss, and by making the second flow path more branches than the first flow path, it is possible to prevent a decrease in the refrigerant speed in the first flow path, and heat can be exchanged with high efficiency in the internal heat exchanger.

The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The scope of the present disclosure is indicated by the claims, not by the description of the embodiments above, and is intended to include all modifications within the meaning and scope of the claims.

1, 1A, 1B, 1C refrigerant circuit, 2 heat medium circuit, 10, 10A, 10B, 10C refrigeration cycle device, 11 compressor, 12 four-way valve, 13 first heat exchanger, 14 first expansion valve, 15, 16, 17, 18, 19 internal heat exchanger, 15a, 15b, 16a, 16b, 17a, 17b, 18a, 18b, 19a, 19b, 20A, 20B, 20C, 20D, 20a, 20b, 20c, 20d, 20e flow path, 20 multi-leaf pipe, 24 second expansion valve, 25 second heat exchanger, 26 fan, 31 radiator, 32 pump, 100 control device, 101 CPU, 102 memory, 111, 112, 113, 114, 115, 116 temperature sensor, 121 pressure sensor.

Claims (8)

A refrigeration cycle device having a refrigerant circuit through which a refrigerant circulates,
the refrigerant circuit includes a compressor, a flow path switching device that switches a flow path of the refrigerant, a first heat exchanger, a first expansion valve, a second expansion valve, a second heat exchanger, and an internal heat exchanger;
The refrigerant circuit is configured such that, during a heating operation, a refrigerant flows through the compressor, the flow path switching device, the first heat exchanger, the first expansion valve, the internal heat exchanger, the second expansion valve, the second heat exchanger, the flow path switching device, the internal heat exchanger, and the compressor in this order;
the internal heat exchanger exchanges heat between a first flow path in which a refrigerant flows between the first expansion valve and the second expansion valve and a second flow path in which a refrigerant flows between the flow path switching device and the compressor,
The second flow path is configured such that the refrigerant branches and merges after heat exchange,
A refrigeration cycle apparatus, wherein a number of branches in the second flow path is greater than a number of branches in the first flow path. the refrigerant circuit is configured such that, by switching the flow path switching device, a flow direction of the refrigerant is reversed in the first flow path, while a flow direction of the refrigerant is not reversed in the second flow path,
During a heating operation, the refrigerant flowing through the first flow path flows in a counter flow direction to the refrigerant flowing through the second flow path,
The refrigeration cycle apparatus according to claim 1 , wherein during a cooling operation, the refrigerant flowing through the first flow passage flows in parallel with the refrigerant flowing through the second flow passage. The refrigeration cycle device according to claim 1 or 2, wherein the capacity of the first heat exchanger is different from the capacity of the second heat exchanger. The refrigeration cycle device according to claim 3, wherein the capacity of the first heat exchanger is smaller than the capacity of the second heat exchanger. A control device for controlling the refrigerant circuit is further provided.
the flow path switching device switches the flow path so that the refrigerant flows differently during a heating operation and a cooling operation,
5. The refrigeration cycle device according to claim 1, wherein the control device controls a frequency of the compressor, an opening degree of the first expansion valve, and an opening degree of the second expansion valve so that, during heating operation, the state of the refrigerant on the inlet side of the internal heat exchanger in the first flow path is a gas-liquid two-phase state, and the state of the refrigerant on the outlet side of the internal heat exchanger is a liquid state. The refrigeration cycle device according to claim 5, wherein the control device controls the frequency of the compressor, the opening of the first expansion valve, and the opening of the second expansion valve so that the state of the refrigerant on the inlet side and the outlet side of the internal heat exchanger in the first flow path is a gas-liquid two-phase state during cooling operation. The first flow path includes a plurality of first auxiliary flow paths,
The second flow path includes a plurality of second auxiliary flow paths,
The first flow path is configured such that the plurality of first auxiliary flow paths are connected in series,
The refrigeration cycle apparatus according to claim 1 , wherein the second flow path is configured such that the plurality of second auxiliary flow paths are arranged in parallel and branched into two or more paths. The first flow path includes a plurality of first auxiliary flow paths,
The second flow path includes a plurality of second auxiliary flow paths,
The first flow path is configured such that the plurality of first auxiliary flow paths are arranged in parallel to each other and branch into two or more branches,
7. The refrigeration cycle apparatus according to claim 1, wherein the second flow path is configured such that the number of second auxiliary flow paths is greater than the number of branches of the first auxiliary flow paths in the first flow path.

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