WO2008013105A1 - Air conditioner - Google Patents

Abstract

A separate type air conditioner using carbon dioxide as the refrigerant sealed in the refrigerant circuit, in which an increase in the amount of consumption of sealed gas used for an air-tightness test performed in site installation work is kept to a minimum and workability of the site installation is less likely to be impaired. For refrigerant connection tubes (6, 7) forming the air conditioner (1), tubes having an outer diameter of not more than 12.7 mm are used when the rated cooling capacity of the air conditioner is not less than 11.2 kW and not more than 14.0 kW, tubes having an outer diameter of not more than 15.9 mm are used when the rated cooling capacity is greater than 14.0 kW and not more than 22.4 kW, tubes having an outer diameter of not more than 19.1 mm are used when the rated cooling capacity is greater than 22.4 kW and not more than 35.5 kW, tubes having an outer diameter of not more than 22.2 mm are used when the rated cooling capacity is greater than 35.5 kW and not more than 45.0 kW, and tubes having an outer diameter of not more than 25.4 mm are used when the rated cooling capacity is greater than 45.0 kW and not more than 56.0 kW.

Description

 Specification

 Air conditioner

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to an air conditioner, and more particularly, to a separate type air conditioner configured by connecting a heat source unit and a utilization unit via a refrigerant communication pipe.

 Background art

 Conventionally, there is a separate type air conditioner configured by connecting a heat source unit and a utilization unit via a refrigerant communication pipe. In such a separate type air conditioner, on-site construction is carried out according to the following procedure.

 First, a heat source unit and a utilization unit are installed, and a refrigerant communication pipe is constructed to construct a refrigerant circuit. Then, after the refrigerant circuit is configured, an airtight test is performed on a portion (hereinafter, referred to as an airtight test target portion) that is an object of an airtight test of the refrigerant circuit including the refrigerant communication pipe using nitrogen gas. After the airtight test is completed, the nitrogen gas sealed in the airtight test target part is discharged to the outside. Then, after exhausting the nitrogen gas, at least the airtight test target part is evacuated. Then, after the evacuation is completed, a predetermined amount of refrigerant is filled in the refrigerant circuit by additionally filling the refrigerant in accordance with the volume of the refrigerant communication tube or by filling the refrigerant circuit with the refrigerant preliminarily sealed in the heat source unit. Refrigerant will be charged.

 [0003] The nitrogen gas used in the above-described airtight test is usually supplied from the nitrogen cylinder to the airtight test target part and boosted to the airtight test pressure. For this reason, in the separate type air conditioner, a nitrogen cylinder is prepared according to the volume of the airtight test target portion of the refrigerant circuit including the refrigerant communication pipe.

 Patent Document 1: JP-A-10-197112

 Disclosure of the invention

[0004] In the separate air conditioner as described above, an HCFC refrigerant such as R22 or an HFC refrigerant such as R407C is often used as the refrigerant enclosed in the refrigerant circuit. However, from the viewpoint of environmental issues, even in a separate type air conditioner, The use of natural refrigerants that have little impact on the environment is being studied, and in particular, nonflammable and non-toxic! / Carbon dioxide is considered promising!

 However, in a force-separated air conditioner, if carbon dioxide is used as the refrigerant enclosed in the refrigerant circuit, the pressure on the high-pressure side in the refrigeration cycle will be about lOMPa, so when using R22 or R407C In comparison, the design pressure of the equipment and piping that make up the refrigerant circuit is very high. If this happens, the pressure of the airtight test in the airtight test performed during the on-site construction of the air conditioner will also increase, so the consumption of nitrogen gas used in the airtight test will increase, and the nitrogen to the target part of the airtight test will increase. The work of supplying gas will take time, and the workability of the local construction will be impaired. In particular, an air conditioner with a large capacity, such as a multi-type air conditioner in which a plurality of utilization units are connected to one or more heat source units, requires a larger amount of nitrogen gas. However, since a large number of nitrogen cylinders are required, and it takes time to replace these nitrogen cylinders, the tendency for the workability of the local construction to be impaired becomes remarkable.

[0005] An object of the present invention is to use a separate type air conditioner that uses carbon dioxide as a refrigerant sealed in a refrigerant circuit, and consumption of an airtight gas used in an airtight test performed during field work. Is to reduce the increase in the amount of work and make the workability of local construction difficult

Yes

 [0006] The air conditioner which is the power of the first invention comprises a refrigerant circuit by connecting one or more heat source units, one or more utilization units, and the heat source units and utilization units. If the refrigerant circuit contains carbon dioxide as a refrigerant and the rated cooling capacity is 11.2 kW or more and 14. OkW or less, the refrigerant connection pipe is A diameter of 12.7 mm or less is used.

 [0007] The air conditioner according to the second aspect of the invention provides a refrigerant circuit in which a refrigerant circuit is configured by connecting one or more heat source units, one or more utilization units, and the heat source units and utilization units. If the refrigerant circuit contains carbon dioxide as the refrigerant and the rated cooling capacity is greater than 14. OkW and less than 22.4 kW, the refrigerant connection tube An outer diameter of 15.9 mm or less is used.

[0008] The air conditioner that is the power of the third invention has one or more heat source units and one or more uses. A refrigerant communication pipe that constitutes a refrigerant circuit by connecting the unit, a heat source unit, and a utilization unit. Carbon dioxide is sealed as refrigerant in the refrigerant circuit, and the rated cooling capacity is 22. If it is greater than 4kW and less than 35.5kW, a refrigerant connection tube with an outer diameter of 19.1mm or less is used.

 [0009] The air conditioner according to the fourth aspect of the present invention provides a refrigerant circuit comprising a refrigerant circuit by connecting one or more heat source units, one or more utilization units, and the heat source units and utilization units. If the refrigerant circuit contains carbon dioxide as the refrigerant and the rated cooling capacity is greater than 35.5 kW and less than 45. OkW, the refrigerant circuit tube An outer diameter of 22.2 mm or less is used.

 [0010] The air conditioner according to the fifth aspect of the present invention provides a refrigerant circuit comprising a refrigerant circuit by connecting at least one heat source unit, at least one utilization unit, and the heat source unit and the utilization unit. When the refrigerant circuit contains carbon dioxide as the refrigerant and the rated cooling capacity is greater than 45. OkW and less than 56. OkW, the refrigerant circuit tube is used as the refrigerant connection tube. An outer diameter of 25.4 mm or less is used.

In this air conditioner, carbon dioxide is used as the refrigerant enclosed in the refrigerant circuit, and the pressure on the high pressure side in the refrigeration cycle is about lOMPa, so the refrigerant has a lower pressure than carbon dioxide such as R22. Compared to the case of using a refrigerant having a saturation pressure characteristic (that is, a characteristic having a high boiling point), it is possible to suppress the performance degradation due to the pressure loss of the refrigerant circulating in the refrigerant circuit. Therefore, in this air conditioner, the volume of the refrigerant communication pipe can be made as small as possible by reducing the diameter of the refrigerant communication pipe within a range where the performance degradation due to pressure loss does not become excessive. Specifically, as described above, when the rated cooling capacity of this air conditioner is 11.2 kW or more and 14. OkW or less, use a refrigerant connection tube with an outer diameter of 12.7 mm or less. Therefore, if the rated cooling capacity of this air conditioner is 14. OkW or more and 22.4 kW or less, use a refrigerant communication pipe with an outer diameter of 15.9 mm or less. When the rated cooling capacity of the air conditioner is 22.4 kW or more and 35.5 kW or less, the rated cooling capacity of this air conditioner can be obtained by using a refrigerant communication pipe with an outer diameter of 19. lmm or less. 35.5 kW or more 4 5. If it is less than OkW, use a refrigerant communication tube with a tube outer diameter of 22.2 mm or less. Therefore, if the rated cooling capacity of this air conditioner is 45. OkW or more and 56. OkW or less, use a refrigerant communication tube with a pipe outer diameter of 25.4mm or less. Compare the volume of the tube to about 1/3 to 1/4 compared to when using R22 as the refrigerant.

 [0011] Thereby, in this air conditioner, the consumption of air-tight gas such as nitrogen gas used in the air-tightness test is increased even though the design pressure of the refrigerant communication pipe is increased by using carbon dioxide as the refrigerant. It is possible to suppress the increase in the amount of work and make it difficult to impair the workability of the local construction.

 Here, the rated cooling capacity is the cooling capacity called under the condition of a rated frequency of 60 Hz in an air conditioner equipped with a compressor driven by a constant speed motor, and is a compression driven by an inverter motor. In an air conditioner equipped with an air conditioner, it refers to the cooling capacity referred to under the condition of the maximum frequency during cooling operation.

 [0012] The air conditioner according to the sixth invention is the air conditioner according to any one of the first to fifth inventions, wherein the heat source unit cools the compressor and the refrigerant compressed in the compressor. A heat source side heat exchanger that can be rejected, and an auxiliary cooler that can further cool the refrigerant cooled in the heat source side heat exchanger.

 In this air conditioner, the heat source side heat exchanger has an auxiliary cooler that can further cool the refrigerant that has been cooled, so performance can be reduced by cooling the refrigerant sent to the use unit. As a result, it is possible to further reduce the performance degradation caused by reducing the diameter of the refrigerant communication pipe.

 [0013] The air conditioner according to the seventh aspect of the invention is the same as the air conditioner according to the sixth aspect of the invention. The refrigerant communication pipe sends the refrigerant cooled in the auxiliary cooler to the utilization unit. And a second refrigerant communication pipe capable of sending refrigerant from the use unit to the heat source unit. The heat source unit is capable of returning to the suction side of the compressor after decompressing a part of the refrigerant flowing from the compressor to the first refrigerant communication pipe through the heat source side heat exchanger and the auxiliary cooler. It has a refrigerant circuit. The auxiliary cooler is a heat exchanger that uses the refrigerant flowing through the auxiliary refrigerant circuit as a cooling source.

In this air conditioner, the refrigerant flowing in the auxiliary refrigerant circuit is used as a cooling source for the auxiliary cooler. Therefore, the flow rate of the refrigerant flowing through the first and second refrigerant communication pipes can be reduced, and the pressure loss of the refrigerant circulating in the refrigerant circuit can be reduced, thereby reducing the diameter of the refrigerant communication pipe. It is possible to further reduce the performance caused by the reduction.

[0014] The air conditioner according to the eighth invention is the same as the air conditioner according to the seventh invention! / The refrigerant cooled by the heat source side heat exchanger is supplied to the auxiliary cooler. Cool further at 20 ° C or more.

 In this air conditioner, the refrigerant cooled by the heat source side heat exchanger is further cooled by 20 ° C or more in the auxiliary cooler, so the effect of improving performance and reducing pressure loss is achieved. You can definitely get it.

 Brief Description of Drawings

 [0015] FIG. 1 is a schematic refrigerant circuit diagram of an air conditioner according to an embodiment of the present invention.

 FIG. 2 is a table showing the relationship between the rated cooling capacity and the diameter of the refrigerant communication pipe in the present invention.

 FIG. 3 is a control block diagram of the air conditioner.

 FIG. 4 is a refrigerant circuit diagram showing a state where a nitrogen cylinder is connected in an airtight test.

 FIG. 5 is a table showing the relationship between the rated cooling capacity and the diameter of the refrigerant communication pipe when R22 is used as the refrigerant.

 FIG. 6 is a table comparing the case where the refrigerant communication pipe according to the present invention is used and the case where the refrigerant pipe having the same pipe inner diameter is used as the refrigerant communication pipe when R22 is used as the refrigerant.

 [Fig. 7] Fig. 7 is a schematic refrigerant circuit diagram of an air-conditioning apparatus according to a modification of the present invention.

 FIG. 8 is a schematic refrigerant circuit diagram of an air-conditioning apparatus according to a modification of the present invention.

 [Fig. 9] Fig. 9 is a schematic refrigerant circuit diagram of an air-conditioning apparatus according to a modification of the present invention.

 Explanation of symbols

[0016] 1 Air conditioner

 2 Heat source unit

 4, 5 Usage unit

 6, 7 Refrigerant communication pipe

 10 Refrigerant circuit

21 Compressor 23 Heat source side heat exchanger

 25 Auxiliary cooler

 61 Auxiliary refrigerant circuit

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of an air conditioner according to the present invention will be described based on the drawings.

 (1) Configuration of air conditioner

 FIG. 1 is a schematic configuration diagram of an air-conditioning apparatus 1 according to an embodiment of the present invention. The air conditioner 1 is an apparatus used for air conditioning in a room such as a building by performing a vapor compression refrigeration cycle operation. In this embodiment, the air conditioner 1 connects one heat source unit 2, a plurality of (in this embodiment, two) use units 4 and 5, and a heat source unit 2 and use units 4 and 5. The first refrigerant communication pipe 6 and the second refrigerant communication pipe 7 are provided as refrigerant communication pipes. That is, the vapor compression refrigerant circuit 10 and the auxiliary refrigerant circuit 61 (described later) of the air-conditioning apparatus 1 of the present embodiment are connected to the heat source unit 2, the utilization units 4, 5, and the refrigerant communication pipes 6, 7. It is a separate type air conditioner configured by the above. Carbon dioxide is sealed as a refrigerant in the refrigerant circuit 10 and the auxiliary refrigerant circuit 61, and is compressed, cooled, depressurized, and evaporated to a pressure exceeding the critical pressure of the refrigerant, as will be described later. Later, the refrigeration cycle operation of being compressed again is started.

[0018] <Usage unit>

 Usage units 4 and 5 are installed in the ceiling of the room, suspended, etc., or installed on the wall surface of the room by wall hanging, etc., installed in the space behind the ceiling or wall, etc. Connected to the indoor space. The utilization units 4 and 5 are connected to the heat source unit 2 via the refrigerant communication pipes 6 and 7 and constitute a part of the refrigerant circuit 10.

Next, the configuration of the usage units 4 and 5 will be described. Since the usage unit 4 and the usage unit 5 have the same configuration, only the configuration of the usage unit 4 will be described here, and the configuration of the usage unit 5 indicates each part of the usage unit 4. Instead of the 40's code, the 50's code is used, and the description of each part is omitted. The usage unit 4 mainly has a usage-side refrigerant circuit 10a (in the usage unit 5, the usage-side refrigerant circuit 10b) that constitutes a part of the refrigerant circuit 10. The utilization side refrigerant circuit 10a mainly includes a utilization side expansion mechanism 41 and a utilization heat exchanger 42.

The use side expansion mechanism 41 is a mechanism for decompressing the refrigerant. In the present embodiment, the use side heat exchanger 42 is used to adjust the flow rate of the refrigerant flowing in the use side refrigerant circuit 10a. It is an electric expansion valve connected to one end. One end of the use side expansion mechanism 41 is connected to the use side heat exchanger 42, and the other end is connected to the first refrigerant communication pipe 6. Note that the use-side expansion mechanism 41 is not limited to an electric expansion valve, but can be any one that has a function of decompressing refrigerant.

 The use side heat exchanger 42 is a heat exchanger that functions as a refrigerant heater or cooler. The utilization heat exchanger 42 has one end connected to the utilization side expansion mechanism 41 and the other end connected to the second refrigerant communication pipe 7.

 In the present embodiment, the usage unit 4 includes a usage-side fan 43 for sucking indoor air into the unit and supplying it to the room again. The usage unit 4 includes a refrigerant flowing through the usage-side heat exchanger 42 and the indoor air. It is possible to exchange heat. The use side fan 43 is a fan motor 4

It is designed to be rotated by 3a.

 The usage unit 4 includes a usage-side control unit 44 that controls the operation of each unit constituting the usage unit 4. The usage-side control unit 44 includes a microcomputer, a memory, and the like provided for controlling the usage unit 4, and a remote controller (not shown) for operating the usage unit 4 individually. Control signals etc. can be exchanged between them, and control signals etc. can be exchanged with the heat source unit 2 via the transmission line 8a.

 <Heat source unit>

 The heat source unit 2 is installed outside and is connected to the usage units 4 and 5 through the refrigerant communication pipes 6 and 7, and the refrigerant circuit 10 is configured between the usage units 4 and 5.

Next, the configuration of the heat source unit 2 will be described. The heat source unit 2 mainly has a heat source side refrigerant circuit 10c constituting a part of the refrigerant circuit 10! /. The heat source side refrigerant circuit 10c mainly includes a compressor 21, a switching mechanism 22, a heat source side heat exchanger 23, and a heat source side expander. The structure 24, the auxiliary cooler 25, the first closing valve 26, and the second closing valve 27 are included.

In the present embodiment, the compressor 21 is a hermetic compressor driven by a compressor drive motor 21a. In the present embodiment, only one compressor 21 is provided. However, the present invention is not limited to this, and two or more compressors 21 may be connected in parallel depending on the number of connected units. Good. The heat source side refrigerant circuit 10c is provided with an accumulator 28 on the suction side of the compressor 21. The accumulator 28 is connected between the switching mechanism 22 and the compressor 21, and is a container capable of accumulating excess refrigerant generated in the refrigerant circuit 10 in accordance with fluctuations in the operating load of the usage units 4 and 5. It is.

 The switching mechanism 22 is a mechanism for switching the direction of the refrigerant flow in the refrigerant circuit 10. During the cooling operation, the heat source side heat exchanger 23 serves as a cooler for the refrigerant compressed by the compressor 21, and In order for the use side heat exchangers 42 and 52 to function as heaters for the refrigerant cooled in the heat source side heat exchanger 23 and the auxiliary cooler 25, the discharge side of the compressor 21 and the heat source side heat exchanger 23 Is connected to the suction side of the compressor 21 and the second shut-off valve 27 (see the solid line of the switching mechanism 22 in Fig. 1). During the heating operation, the use side heat exchangers 42 and 52 are connected. In order to function as a refrigerant cooler to be compressed by the compressor 21 and the heat source side heat exchanger 23 as a refrigerant heater cooled by the use side heat exchangers 42 and 52, Connects the discharge side of the compressor 21 and the second closing valve 27 and heats the suction side of the compressor 21 and heat. It is possible to connect the one end side heat exchanger 23 (see dashed switching mechanism 22 in FIG. 1). In the present embodiment, the switching mechanism 22 is a four-way switching valve connected to the suction side of the compressor 21, the discharge side of the compressor 21, the heat source side heat exchanger 23, and the second closing valve 27. Note that the switching mechanism 22 is not limited to a four-way switching valve, and is configured to have a function of switching the refrigerant flow direction similar to that described above, for example, by combining a plurality of solenoid valves. May be.

The heat source side heat exchanger 23 is a heat exchanger that functions as a refrigerant cooler or heater.

 One end of the heat source side heat exchanger 23 is connected to the switching mechanism 22, and the other end is connected to the heat source side expansion mechanism 24! /.

The heat source unit 2 has a heat source side fan 29 for sucking outdoor air into the unit and discharging it outside the room again. The heat source side fan 29 is composed of outdoor air and a heat source side heat exchanger. It is possible to exchange heat with the refrigerant flowing through 23. The heat source side fan 29 is rotationally driven by a fan motor 29a. Note that the heat source of the heat source side heat exchanger 23 may be another heat medium such as water, which is not limited to outdoor air. The heat source side expansion mechanism 24 is a mechanism for decompressing the refrigerant. In this embodiment, the other end of the heat source side heat exchanger 23 is used to adjust the flow rate of the refrigerant flowing in the heat source side refrigerant circuit 10c. It is an electric expansion valve connected to. One end of the heat source side expansion mechanism 24 is connected to the heat source side heat exchanger 23, and the other end is connected to the auxiliary cooler 25. It should be noted that the heat source side expansion mechanism 24 is not limited to the electric expansion valve, but may have any function that depressurizes the refrigerant. The heat source side refrigerant circuit 10c is provided with a check mechanism 30 so as to bypass the heat source side expansion mechanism 24. The check mechanism 30 is a mechanism that allows a refrigerant flow in one direction and blocks a refrigerant flow in the reverse direction. In this embodiment, the heat source side heat exchanger 23 This is a check valve provided to block the flow of refrigerant from the auxiliary cooler 25 to the heat source side heat exchanger 23. is there.

The auxiliary cooler 25 is a heat exchanger that can further cool the refrigerant cooled by the heat source side heat exchanger 23. The auxiliary cooler 25 has one end connected to the heat source side heat exchanger 23 and the other end connected to the first closing valve 26. In the present embodiment, the auxiliary cooler 25 is a double-pipe heat exchanger. . Further, in the heat source side refrigerant circuit 10c, a part of the refrigerant flowing from the compressor 21 to the first shutoff valve 26 through the heat source side heat exchanger 23 and the auxiliary cooler 25 is decompressed, and then the suction side of the compressor 21 is An auxiliary refrigerant circuit 61 that can be returned to is provided. In the present embodiment, the auxiliary refrigerant circuit 61 divides a part of the refrigerant flowing between the heat source side expansion mechanism 24 and the auxiliary cooler 25 from the refrigerant circuit 10, and specifically, the suction side beam of the compressor 21. The refrigerant circuit 10 is connected back to the switching mechanism 22 and the accumulator 28. The auxiliary refrigerant circuit 61 includes a branch circuit 6 la branched from a position between the heat source side expansion mechanism 24 and the auxiliary cooler 25 to reach the inlet of the auxiliary cooler 25 on the auxiliary cooling circuit 61 side, and the auxiliary cooler 25, a merging circuit 61b that merges from the outlet on the auxiliary cooling circuit 61 side to a position between the switching mechanism 22 and the accumulator 28 is provided. The branch circuit 61a is provided with an auxiliary expansion mechanism 62. The auxiliary expansion mechanism 62 depressurizes the refrigerant. In the present embodiment, this is an electric expansion valve provided for adjusting the flow rate of the refrigerant flowing through the auxiliary refrigerant circuit 61. Thereby, a part of the refrigerant cooled in the heat source side heat exchanger 23 is bypassed to the suction side of the compressor 21 by the auxiliary refrigerant circuit 61, and the refrigerant flowing through the auxiliary refrigerant circuit 61 in the auxiliary cooler 25. It is further cooled by using as a cooling source.

[0024] The first closing valve 26 is a valve to which the first refrigerant communication pipe 6 for exchanging refrigerant between the heat source unit 2 and the utilization units 4 and 5 is connected, and is connected to the auxiliary cooler 25. ing. The second closing valve 27 is a valve to which a second refrigerant communication pipe 7 for exchanging refrigerant between the heat source unit 2 and the utilization units 4 and 5 is connected, and is connected to the switching mechanism 22. Here, the first and second closing valves 26 and 27 are three-way valves having a service port that can communicate with the outside of the refrigerant circuit 10.

 The heat source unit 2 is provided with various sensors. Specifically, the heat source unit 2 has a heat source that detects the refrigerant temperature Tco at the outlet of the heat source side heat exchanger 23 when the heat source side heat exchanger 23 functions as a refrigerant cooler. A side heat exchanger temperature sensor 31 is provided! When the auxiliary cooler 25 is made to function as a cooler that further cools the refrigerant cooled by the heat source side heat exchanger 23! /, The refrigerant of the refrigerant circuit 10 side of the auxiliary cooler 25 is connected to the outlet of the refrigerant. An auxiliary cooler temperature sensor 32 for detecting the temperature Tsc is provided. In the present embodiment, the heat source side heat exchanger temperature sensor 31 and the auxiliary cooler temperature sensor 32 are thermistors. In addition, the heat source unit 2 includes a heat source side control unit 33 that controls the operation of each unit constituting the heat source unit 2. The heat source side control unit 33 includes a microcomputer, a memory, and the like provided to control the heat source unit 2, and transmits data to and from the usage side control units 44 and 54 of the usage units 4 and 5. Control signals can be exchanged via line 8a.

[0025] <Refrigerant tube>

Refrigerant communication pipes 6 and 7 are refrigerant pipes installed on site when the air conditioner 1 is installed at the installation site. The first refrigerant communication pipe 6 is a junction pipe connecting the branch pipes 6a and 6b connected to each of the usage units 4 and 5 and a portion where the branch pipe 6a and the branch pipe 6b merge with the first closing valve 26. 6c. The second refrigerant communication pipe 7 is a branch pipe 7a connected to each usage unit 4 and 5. 7b, and a junction pipe 7c connecting the portion where the branch pipe 7a and the branch pipe 7b merge with the second closing valve 27. The total amount of refrigerant exchanged between the use units 4 and 5 and the heat source unit 2 flows through the junction pipes 6c and 7c. That is, each of the refrigerant communication tubes 6 and 7 has a plurality of usage units 4 and 5 when a plurality of usage units 4 and 5 are connected to a single heat source unit 2 as in this embodiment. And the heat source unit 2 have the junction pipes 6c and 7c, which are the parts where the total amount of refrigerant exchanged, and the exchange of refrigerant between the plurality of usage units 4 and 5 and the heat source unit 2 Except for the parts close to the usage units 4 and 5, these joint pipes 6c and 7c are generally used. Unlike this embodiment, when one utilization unit is connected to one heat source unit, each refrigerant communication pipe is only in the portion corresponding to the merge pipes 6c and 7c in this embodiment. Therefore, the refrigerant is exchanged between the use mute and the heat source mute. In addition, when one utilization unit is connected to a plurality of heat source units, each refrigerant communication pipe has a portion corresponding to the branch pipes 6a, 6b, 7a, 7b in this embodiment. In addition to being provided for branching between the units, the parts corresponding to the junction pipes 6c and 7c in this embodiment are provided so as to connect the parts corresponding to these branch pipes and the utilization unit. In the present embodiment, the refrigerant is exchanged between the use mute and the heat source mute by the portions corresponding to the junction pipes 6c and 7c. Further, when a plurality of usage units are connected to a plurality of heat source units, each refrigerant communication pipe has a portion corresponding to the branch pipes 6a, 6b, 7a, 7b in this embodiment. Provided for branching between units and for branching between multiple heat source units, a part corresponding to the branch pipe on the heat source unit side and a part corresponding to the branch pipe on the use unit side A portion corresponding to the junction pipes 6c and 7c in the present embodiment is provided so as to connect them, and a portion corresponding to the junction pipes 6c and 7c in the present embodiment is generally provided between the use mut and the heat source mut. The refrigerant will be exchanged.

As described above, these refrigerant communication pipes 6 and 7 have various pipe diameters and lengths depending on the conditions of the apparatus capacity determined by the combination of the utilization unit and the heat source unit, the conditions of the installation location, etc. Will be used. In this embodiment, as shown in FIG. 2, the diameters of the refrigerant communication pipes 6 and 7 are selected according to the rated cooling capacity. Here, the rated cooling capacity means the cooling capacity called under the condition of a rated frequency of 60 Hz when the compressor drive motor 21a is a constant speed motor, and the compressor drive motor 21a is an inverter motor. In some cases, it refers to the cooling capacity referred to under the condition of maximum frequency during cooling operation. The value of the diameter of the first refrigerant communication pipe 6 shown in FIG. 2 is the first refrigerant communication pipe excluding members such as pipe joints for connecting the branch pipes 6a, 6b and the merge pipe 6c. 6 (that is, the maximum value of the diameter of the merging pipe 6c), and the branch pipes 6a and 6b are refrigerant pipes having a pipe diameter smaller than that shown in FIG. Is used. Also, the value of the diameter of the second refrigerant communication pipe 7 shown in FIG. 2 is the second refrigerant communication pipe excluding members such as pipe joints for connecting the branch pipes 7a, 7b and the junction pipe 7c. 7 (that is, the maximum value of the diameter of the merging pipe 7c), and the branch pipes 7a and 7b are refrigerant pipes having a pipe diameter smaller than that shown in FIG. Is used. In FIG. 2, the outer diameter D and the inner diameter d are shown as the pipe diameter values. Of these, the inner diameter d takes into consideration the refrigerant pressure (about lOMPa) on the high pressure side in the refrigeration cycle operation. The values of the pipe diameter excluding the pipe thickness when the design pressure of the refrigerant communication pipes 6 and 7 is set to 12 MPa are shown. Note that the value of the diameter of the second refrigerant communication pipe 7 is larger than the value of the diameter of the first refrigerant communication pipe 6! / For the reason during cooling operation! This is due to the low-pressure (about 4MPa) gas state refrigerant flowing in the refrigeration cycle operation. Therefore, the refrigerant communication pipes 6 and 7 of the air conditioner 1 are used as a whole with a refrigerant pipe having a pipe diameter equal to or smaller than the pipe diameter of the second refrigerant communication pipe 7 shown in FIG. . Fig. 2 is a table showing the relationship between the rated cooling capacity and the diameter of the refrigerant communication pipes 6 and 7. Both of the refrigerant communication pipes 6 and 7 are phosphorus-deoxidized copper seamless copper pipes (JI S C1220T—1 / 2H) is used.

As a result, when the rated cooling capacity of the air conditioner 1 is 11.2 kW or less, the outer diameter D of the refrigerant communication pipes 6 and 7 as a whole is 12.7 mm or less (or the inner diameter d of the pipe is 10. More specifically, the first refrigerant communication pipe 6 has a pipe outer diameter D of 6.35 mm (or pipe inner diameter d of 5.15 mm or less). For the second refrigerant communication tube 7, the outer diameter D of the tube is 12.7 mm or less (or the inner diameter d of the tube is 10.4 mm or less). Is used.

 When the rated cooling capacity of the air conditioner 1 is 11.2 kW or more and 14. OkW or less, the refrigerant communication pipes 6 and 7 as a whole have a pipe outer diameter D of 12.7 mm or less (or a pipe inner diameter d of More specifically, the outer diameter D of the first refrigerant communication pipe 6 is 7.94 mm (or the inner diameter d of the pipe is 6.44 mm). The following is used, and for the second refrigerant communication pipe 7, the pipe outer diameter D is 12.7 mm or less (or the pipe inner diameter d is 10.4 mm or less).

[0028] If the rated cooling capacity of the air conditioner 1 is greater than 14. OkW and 16. OkW or less, the refrigerant communication pipes 6 and 7 as a whole have a pipe outer diameter D of 15.9 mm or less (or Tube inner diameter d force Omm or less), and more specifically, for the first refrigerant communication tube 6, the outer diameter D of the tube is 7.94 mm (or the inner diameter d of the tube is 6. 44mm or less) is used, and for the second refrigerant communication pipe 7, a pipe outer diameter D of 15.9 mm or less (or pipe inner diameter d of 13. Omm or less) is used.

 If the rated cooling capacity of the air conditioner 1 is greater than 16. OkW and less than 22.4 kW, the outer diameter D of the refrigerant communication pipes 6 and 7 as a whole is 15.9 mm or less (or the inner diameter of the pipe). More specifically, for the first refrigerant communication pipe 6, the outer diameter D is 9.52 mm (or the inner diameter d is 7.72 mm or less). For the second refrigerant communication pipe 7, the pipe outer diameter D is 15.9 mm or less (or the pipe inner diameter d is 13.3 mm or less).

[0029] When the rated cooling capacity of the air conditioner 1 is greater than 22.4kW and 28. OkW or less, the refrigerant communication pipes 6 and 7 as a whole have a pipe outer diameter D of 19.1mm or less (or Tube inner diameter d force 6mm or less), and more specifically, for the first refrigerant communication tube 6, the outer diameter D is 9.52mm (or the inner diameter d is 7.). 72mm or less) is used, and for the second refrigerant communication pipe 7, the pipe outer diameter D is 19.1 mm or less (or the pipe inner diameter d is 15.6 mm or less).

If the rated cooling capacity of the air conditioner 1 is greater than 28. OkW and 35.5 kW or less, the refrigerant communication pipes 6 and 7 as a whole have a pipe outer diameter D of 19.1 mm or less (or pipe inner diameter). d force 6mm or less), and more specifically, the first refrigerant communication pipe 6 , The pipe outer diameter D is 12.7 mm (or the pipe inner diameter d is 10.4 mm or less), and the second refrigerant communication pipe 7 has a pipe outer diameter D of 19.1 mm or less (or Pipe inner diameter d is 1

5. 6mm or less) is used.

 [0030] When the rated cooling capacity of the air conditioner 1 is greater than 35.5 kW and less than 45. OkW, the refrigerant communication pipes 6 and 7 as a whole have a pipe outer diameter D of 22.2 mm or less (or , And more specifically, for the first refrigerant communication pipe 6, the pipe outer diameter D is 12.7 mm (or the pipe inner diameter d is less than 1 mm). 10.4 mm or less) is used, and for the second refrigerant communication pipe 7, a pipe outer diameter D of 22.2 mm or less (or pipe inner diameter d of 18.2 mm or less) is used.

 If the rated cooling capacity of the air conditioner 1 is greater than 45. OkW and 56. OkW or less, the refrigerant communication pipes 6 and 7 as a whole have a pipe outer diameter D of 25.4 mm or less (or pipe inner diameter). d force ¾0 · 8mm or less) is used. More specifically, for the first refrigerant communication pipe 6, the pipe outer diameter D is 12.7 mm (or the pipe inner diameter d is 10.4 mm). The following are used, and for the second refrigerant communication pipe 7, the pipe outer diameter D is 25.4 mm or less (or the pipe inner diameter d is 20.8 mm or less).

 [0031] As described above, the use side refrigerant circuits 10a and 10b, the heat source side refrigerant circuit 10c, and the refrigerant communication pipe

6 and 7 are connected to form the refrigerant circuit 10 together with the auxiliary refrigerant circuit 61. The air conditioner 1 according to the present embodiment includes the use side control units 44 and 54, the heat source side control unit 33, and the transmission line 8a connecting the control units 33, 44, and 54. A control unit 8 is configured as a control means for performing various operation controls. As shown in FIG. 3, the control unit 8 is connected so as to be able to receive detection signals of various sensors 31 and 32, and based on these detection signals and the like, various devices and valves 21, 22, 24 29, 41, 43, 51, 53, 62 are connected so that they can be controlled. Here, FIG. 3 is a control block diagram of the air conditioner 1.

 (2) Local construction of air conditioner

 Next, the local construction of the air conditioner 1 will be described.

[0032] <Equipment installation (refrigerant circuit configuration)>

First, use units 4, 5 and heat source unit 2 are installed at the installation location, and refrigerant communication pipe 6, 7 is constructed and connected to the use units 4 and 5 and the heat source unit 2 to constitute the refrigerant circuit 10 of the air conditioner 1. Here, the shutoff valves 26 and 27 of the heat source unit 2 are closed, and the heat source side refrigerant circuit 10c and the refrigerant communication pipes 6 and 7 are not in communication with each other. In the heat source side refrigerant circuit 10c of the heat source unit 2, carbon dioxide as a refrigerant is sealed in advance.

 <Airtight test>

 After the refrigerant circuit 10 of the air conditioner 1 is configured, an airtight test of the refrigerant communication pipes 6 and 7 is performed. When the usage units 4 and 5 are in communication with the refrigerant communication tubes 6 and 7, the airtight test of the refrigerant communication tubes 6 and 7 is performed in a state where the usage units 4 and 5 are in communication.

 First, nitrogen gas as an airtight gas is supplied to the airtight test target portion of the refrigerant circuit 10 including the refrigerant communication tubes 6 and 7, and the airtight test target portion is pressurized to the airtight test pressure. In the present embodiment, the nitrogen gas is supplied by connecting a nitrogen cylinder 9 to the service port of the second closing valve 27 as shown in FIG. The place where the nitrogen cylinder 9 is connected is not limited to the service port of the second closing valve 27 but may be the service port of the first closing valve 26, or a separate charge port is provided for the refrigerant communication pipes 6 and 7. If this is the case, a nitrogen cylinder 9 may be connected to this charge port. Then, after the supply of nitrogen gas is stopped, it is confirmed that the airtight test pressure is maintained for a predetermined test time for the target portion of the airtight test. FIG. 4 is a refrigerant circuit diagram showing a state in which a nitrogen cylinder is connected in the airtight test.

Here, in the air conditioner 1, as described above, carbon dioxide is used as the refrigerant, and the pressure on the high pressure side in the refrigeration cycle becomes a pressure exceeding the critical pressure (about lOMPa). The design pressure of the equipment and piping of the refrigerant circuit 10 and the auxiliary refrigerant circuit 61 in which the refrigerant of the high-pressure side refrigerant flows is set to a higher pressure, and accordingly, the hermetic test pressure increases according to the design pressure. Set to pressure. In the present embodiment, the design pressure on the high pressure side of the refrigerant circuit 10 and the auxiliary refrigerant circuit 61 is set to 12 MPa, and the airtight test target portion including the refrigerant communication pipes 6 and 7 includes the high pressure side in the refrigeration cycle. Therefore, the air tightness test pressure is set to 12MPa, which is the same as the design pressure on the high pressure side. Therefore, when using R22 or R407C as the refrigerant Compared to the above, the consumption of nitrogen gas used in the airtight test tends to increase.

However, in this embodiment, as shown in FIGS. 2 and 5, the diameter of the refrigerant communication pipes 6 and 7 is selected so as to be smaller than when R22 or R407C is used as the refrigerant. Therefore, the use of carbon dioxide as the refrigerant increases the design pressure of the refrigerant communication pipes 6 and 7, but suppresses an increase in nitrogen gas consumption in the airtight test.

 Specifically, for the refrigerant communication pipes 6 and 7, if a refrigerant pipe having the same pipe inner diameter d as the refrigerant used for R22 is used, as shown in FIG. Here, it is assumed that a generally used charging pressure of 14.7 MPa and an internal volume of 471 is used), but the rated cooling capacity is in the range of 11.2 kW to 56. OkW. When the length of 7 is assumed to be 100 m, a large number of 3 to 7 is required, whereas the refrigerant communication pipes 6 and 7 of this embodiment (that is, as shown in FIG. 2) When the pipe diameter is reduced, the volume VI of the refrigerant communication pipes 6 and 7 is used as shown in Fig. 6 and the volume VI of the refrigerant communication pipes 6 and 7 is used as the refrigerant (in this case, the refrigerant communication pipes 6 and 7 The volume can be reduced to about 1/3 to 1/4 compared with the volume V2). As a result, the number of nitrogen cylinders used can be reduced. In rated cooling capacity 11. 2KW～56. Range OKW, it can be reduced to two-three per 100m refrigerant communication pipe. As a result, the increase in the consumption of nitrogen gas in the airtight test can be suppressed, and the increase in the trouble of replacing the nitrogen cylinder can be suppressed as much as possible. In addition, since the weight of the refrigerant communication pipes 6 and 7 themselves can be reduced, the material cost of the refrigerant communication pipes 6 and 7 can be reduced. FIG. 5 is a table showing the relationship between the rated cooling capacity and the diameter of the refrigerant communication pipe when R22 is used as the refrigerant. FIG. 6 is a table comparing the case where the refrigerant communication pipe according to the present invention is used and the case where the refrigerant pipe having the same pipe inner diameter is used as the refrigerant communication pipe when R22 is used as the cooling medium.

[0035] <Airtight gas release>

After the airtight test is completed, in order to reduce the pressure in the airtight test target part, nitrogen gas in the airtight test target part is released into the atmosphere. Here, in the atmospheric discharge work, in order to prevent the intrusion of air from the outside of the refrigerant circuit 10, the airtight test target part including the refrigerant communication pipes 6 and 7 is used. The pressure of the minute is slightly higher than the atmospheric pressure!

 <Evacuation>

 After the release of nitrogen gas, in order to completely remove the nitrogen gas from the target part of the hermetic test, an airtight test is performed by connecting a vacuum pump to the service ports of the shut-off valves 26 and 27 (not shown here). Vacuum the target part.

 <Refrigerant filling>

 After the evacuation is completed, an operation for filling the refrigerant circuit 10 as a whole with the refrigerant previously enclosed in the heat source side refrigerant circuit 10c by opening the closing valves 26 and 27 is performed. In addition, as in the case where the refrigerant communication pipes 6 and 7 are long, etc., the refrigerant amount required for the entire refrigerant circuit 10 can be satisfied only by the amount of refrigerant previously enclosed in the heat source side refrigerant circuit 10c! In some cases, the work of refilling the refrigerant from the outside is carried out by adding a refrigerant cylinder to the service ports of the shut-off valves 26, 27, etc. during or before the opening of the shut-off valves 26, 27. To connect.

 (3) Air conditioner operation

 Next, the operation of the air conditioner 1 of the present embodiment will be described.

 <Cooling operation>

During the cooling operation, the switching mechanism 22 is in the state indicated by the solid line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the heat source side heat exchanger 23, and the suction side of the compressor 21 is the second closing valve 2 7 It is in a connected state. The heat source side expansion mechanism 24 is fully closed. The shut-off valves 26 and 27 are open. The opening degree of each use side expansion mechanism 41, 51 is adjusted according to the load of the use side heat exchangers 42, 52. In addition, the auxiliary expansion mechanism 62 is configured such that the refrigerant temperature Tsc at the outlet on the refrigerant circuit 10 side of the auxiliary cooler 25 is 20 ° C higher than the refrigerant temperature Tco at the outlet of the heat source side heat exchanger 23 that functions as a refrigerant cooler. The opening is adjusted so that it is even lower. The opening degree control of the auxiliary expansion mechanism 62 can be performed using various operation state quantities of the refrigerant circuit 10 and the auxiliary refrigerant circuit 61. In this embodiment, the heat source that detects the temperature Tco is used. Using the side heat exchanger temperature sensor 31 and the auxiliary cooler temperature sensor 32 that detects the temperature Tsc, the temperature difference Δ Τ is obtained by subtracting the value of Tco, the value of Tsc, and the value of Tsc. When the temperature is less than 20 ° C, control is performed to increase the opening of the auxiliary expansion mechanism 62. [0037] In the state of the refrigerant circuit 10 and the auxiliary refrigerant circuit 61, when the compressor 21, the heat source side fan 29 and the use side fans 43 and 53 are started, the low-pressure (about 4 MPa) refrigerant is sucked into the compressor 21. As a result, the refrigerant is compressed to a pressure exceeding the critical pressure to become a high-pressure (about 1 OMPa) refrigerant. Thereafter, the high-pressure refrigerant is sent to the heat source side heat exchanger 23 via the switching mechanism 22, and is cooled by exchanging heat with outdoor air supplied by the heat source side fan 29. Then, the high-pressure refrigerant cooled in the heat source side heat exchanger 23 passes through the check mechanism 30 and flows into the auxiliary cooler 25 to further exchange heat with the refrigerant flowing through the auxiliary refrigerant circuit 61. Cool above ° C. At this time, a portion of the high-pressure refrigerant cooled in the heat source side heat exchanger 23 is branched into the auxiliary refrigerant circuit 61, and after being depressurized by the auxiliary expansion mechanism 62, is returned to the suction side of the compressor 21. Then, the refrigerant flowing from the outlet of the auxiliary expansion mechanism 62 of the auxiliary refrigerant circuit 61 toward the suction side of the compressor 21 passes through the auxiliary cooler 25 and is heated with the high-pressure refrigerant flowing through the refrigerant circuit 10 side. It is heated by exchange.

 Then, the high-pressure refrigerant cooled in the auxiliary cooler 25 is sent to the usage units 4 and 5 via the first closing valve 26 and the first refrigerant communication pipe 6. The high-pressure refrigerant sent to the usage units 4 and 5 is decompressed by the usage-side expansion mechanisms 41 and 51 to become a low-pressure gas-liquid two-phase refrigerant and sent to the usage-side heat exchangers 42 and 52. In each of the usage-side heat exchangers 42 and 52, heat is exchanged with room air to be heated and evaporate to become a low-pressure refrigerant.

 The low-pressure refrigerant heated in the use-side heat exchangers 42, 52 is sent to the heat source unit 2 via the second refrigerant communication pipe 7, and is sent to the heat source unit 2 via the second closing valve 27 and the switching mechanism 22. Flows into the accumulator 28. Then, the low-pressure refrigerant flowing into the accumulator 28 is sucked into the compressor 21 again.

 <Heating operation>

During the heating operation, the switching mechanism 22 is in the state indicated by the broken line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the second closing valve 27, and the suction side of the compressor 21 is the heat source side heat exchanger 2 3 It is in a connected state. The opening degree of the heat source side expansion mechanism 24 is adjusted in order to reduce the refrigerant to a pressure at which the refrigerant can be evaporated in the heat source side heat exchanger 23. Further, the first closing valve 26 and the second closing valve 27 are opened. User side swelling The tension mechanisms 41 and 51 are adjusted in opening according to the load on the use side heat exchangers 42 and 52. The auxiliary expansion mechanism 62 is closed.

 [0039] In the state of the refrigerant circuit 10 and the auxiliary refrigerant circuit 61, the compressor 21, the heat source side fan

 When 29 and the use side fans 43 and 53 are started, the low-pressure (about 4 MPa) refrigerant is sucked into the compressor 21 and compressed to a pressure exceeding the critical pressure to become a high-pressure (about lOMPa) refrigerant. The high-pressure refrigerant is sent to the usage units 4 and 5 via the switching mechanism 22, the second closing valve 27 and the second refrigerant communication pipe 7.

 Then, the high-pressure refrigerant sent to the usage units 4 and 5 is cooled by exchanging heat with room air in the usage-side heat exchangers 42 and 52, and is then passed through the usage-side expansion mechanisms 41 and 51. When passing, the pressure is reduced according to the opening degree of each use side expansion mechanism 41, 51.

 The refrigerant that has passed through the use side expansion mechanisms 41 and 51 is sent to the heat source unit 2 via the first refrigerant communication pipe 6 and passes through the first closing valve 26, the auxiliary cooler 25, and the heat source side expansion mechanism 24. The pressure is further reduced, and then flows into the heat source side heat exchanger 23. Then, the low-pressure gas-liquid two-phase refrigerant flowing into the heat source side heat exchanger 23 evaporates by being heated by exchanging heat with the outdoor air supplied by the heat source side fan 29 to become a low pressure refrigerant. Then, it flows into the accumulator 24 via the switching mechanism 22. Then, the low-pressure refrigerant that has flowed into the accumulator 24 is sucked into the compressor 21 again.

 [0040] The operation control in the cooling operation and the heating operation as described above is performed by the control unit 8 functioning as an operation control unit. Specifically, the use side control units 44 and 54, the heat source side control unit 33, and the control unit 33 , 44, 54 is performed by a transmission line 8a).

 (4) Features of the air conditioner

 The air conditioner 1 of the present embodiment has the following features.

 (A)

In the air conditioner 1 of the present embodiment, carbon dioxide is used as the refrigerant enclosed in the refrigerant circuit 10 and the auxiliary refrigerant circuit 61, and the pressure on the high pressure side in the refrigeration cycle is about lOMPa. Compared to the case of using a refrigerant with a saturation pressure characteristic lower than that of carbon dioxide such as R22 (that is, a characteristic with a high boiling point), it is possible to suppress the performance degradation due to the pressure loss of the refrigerant circulating in the refrigerant circuit 10 become. So this In the air conditioner 1, the volume of the refrigerant communication pipes 6 and 7 can be reduced as much as possible by reducing the pipe diameters of the refrigerant communication pipes 6 and 7 within a range where performance degradation due to pressure loss does not become excessive. Monkey.

 [0041] Specifically, when the rated cooling capacity is 11.2 kW or more and 14. OkW or less, the pipe outer diameter D of the refrigerant communication pipes 6 and 7 as a whole is 12.7 mm or less (the pipe inner diameter d is 10. If the rated cooling capacity is greater than 14. OkW and less than 22.4 kW, the outer diameter D of the refrigerant communication pipes 6 and 7 as a whole is less than 15.9 mm (the inner diameter of the pipe). If the rated cooling capacity is greater than 22.4 kW and less than 35.5 kW, the outer diameter D of the refrigerant communication pipes 6 and 7 as a whole is 19. If the rated cooling capacity is greater than 35.5 kW and less than 45. OkW by using a tube with a diameter of 1 mm or less (pipe inner diameter d is 15.6 mm or less), the outer diameter of the refrigerant communication pipe 6, 7 as a whole By using a tube with a D of 22.2 mm or less (pipe inner diameter d force 2 mm or less), the rated cooling capacity is larger than 45. OkW. By using a pipe with an outer diameter D of 25.4 mm or less (with an inner diameter d of 25.4 mm or less), the capacity of the refrigerant communication pipes 6 and 7 is smaller than when using R22 as the cooling medium. 1/3 to 1/4.

 [0042] Thus, in this air conditioner 1, the use of carbon dioxide as the refrigerant increases the design pressure of the refrigerant communication tubes 6 and 7, but the airtightness of nitrogen gas or the like used in the airtightness test is increased. The increase in gas consumption can be suppressed, and the workability of local construction can be impaired.

 (B)

 The air conditioner 1 of the present embodiment has the auxiliary cooler 25 that can further cool the refrigerant cooled in the heat source side heat exchanger 23, and therefore cools the refrigerant sent to the utilization units 4 and 5. As a result, the performance can be improved, so that the performance degradation caused by reducing the diameter of the refrigerant communication pipes 6 and 7 can be further prevented.

Moreover, since the refrigerant flowing through the auxiliary refrigerant circuit 61 is used as a cooling source for the auxiliary cooler 25, the flow rate of the refrigerant flowing through the first and second refrigerant communication pipes 6 and 7 is reduced, and the refrigerant circuit 10 The pressure loss of the circulating refrigerant can be reduced, so that the refrigerant connecting pipe 6, 7 The performance degradation caused by reducing the pipe diameter can be further reduced.

 [0043] In particular, in the air conditioner 1 of the present embodiment, the refrigerant cooled in the heat source side heat exchanger 23 is cooled further by 20 ° C or more in the auxiliary cooler 25. The effect of improving performance and reducing pressure loss can be reliably obtained.

 (5) Modification

 In the above-described embodiment, the auxiliary refrigerant circuit 61 in which the refrigerant as the cooling source of the auxiliary cooler 25 flows passes a part of the refrigerant flowing between the heat source side expansion mechanism 24 and the auxiliary cooler 25. It is possible to supply a refrigerant capable of further cooling the refrigerant cooled in the power heat source side heat exchanger 23 provided to be branched from the refrigerant circuit 10 and returned to the suction side of the compressor 21. In addition, since it is only necessary to reduce the flow rate of the refrigerant flowing through the first and second refrigerant communication pipes 6 and 7, as shown in FIG. 7, the heat source side heat exchanger 23 and the heat source side expansion mechanism 24 A part of the refrigerant flowing between them is branched from the refrigerant circuit 10 and returned to the suction side of the compressor 21! /.

Further, as shown in FIG. 8, the auxiliary refrigerant circuit 61 causes a part of the refrigerant flowing between the auxiliary cooler 25 and the first closing valve 26 to branch from the refrigerant circuit 10 so that the compressor 21 It may be provided to return to the suction side.

 In this case, compared with the above-described embodiment, the processing flow rate of the refrigerant flowing on the refrigerant circuit 10 side of the auxiliary cooler 25 is increased. In addition to the cooling in the heat source side heat exchanger 23, the auxiliary cooler 25 further cools. The refrigerant that has flown to the refrigerant circuit 10 side of the auxiliary cooler 25 can be cooled using the refrigerant that has been discharged.

 Further, as shown in FIG. 9, the auxiliary refrigerant circuit 61 may be provided so that a part of the cooling medium flowing in the heat source side heat exchanger 23 is branched and returned to the suction side of the compressor 21. . In this case, since the processing flow rate of the refrigerant in the heat source side heat exchanger 23 downstream of the connection part of the auxiliary refrigerant circuit 61 is reduced, the downstream of the connection part of the auxiliary refrigerant circuit 61. Cooling of the refrigerant in the side heat source side heat exchanger 23 can be promoted.

[0045] (6) Other embodiments

As mentioned above, the force specific structure which demonstrated embodiment of this invention based on drawing is as follows. The present invention is not limited to these embodiments, and modifications can be made without departing from the spirit of the invention.

Industrial applicability

 If the present invention is used, consumption of airtight gas used in an airtight test performed at the time of on-site construction will be reduced to a separate type air conditioner that uses carbon dioxide as the refrigerant enclosed in the refrigerant circuit. The increase in the volume can be suppressed, and the workability of local construction can be impaired.

Claims

The scope of the claims [1] One or more heat source units (2),  One or more units (4, 5),  A refrigerant communication pipe (6, 7) constituting a refrigerant circuit (10) by connecting the heat source unit and the utilization unit;  In the refrigerant circuit, carbon dioxide is sealed as a refrigerant,  When the rated cooling capacity is 11.2 kW or more and 14. OkW or less, the refrigerant communication pipe having a pipe diameter of 12.7 mm or less is used.  Air conditioner (1). [2] one or more heat source units (2),  One or more units (4, 5),  A refrigerant communication pipe (6, 7) constituting a refrigerant circuit (10) by connecting the heat source unit and the utilization unit;  In the refrigerant circuit, carbon dioxide is sealed as a refrigerant,  When the rated cooling capacity is greater than 14. OkW and equal to or less than 22.4 kW, the refrigerant connection tube having a diameter of 15.9 mm or less is used.  Air conditioner (1). [3] one or more heat source units (2),  One or more units (4, 5),  A refrigerant communication pipe (6, 7) constituting a refrigerant circuit (10) by connecting the heat source unit and the utilization unit;  In the refrigerant circuit, carbon dioxide is sealed as a refrigerant,  If the rated cooling capacity is greater than 22.4kW and less than or equal to 35.5kW, the refrigerant connection tube with an outer diameter of 19.1mm or less is used.  Air conditioner (1). [4] One or more heat source units (2),  One or more units (4, 5), A refrigerant circuit (10) is formed by connecting the heat source unit and the utilization unit. And refrigerant connecting pipes (6, 7)  In the refrigerant circuit, carbon dioxide is sealed as a refrigerant,  If the rated cooling capacity is greater than 35.5 kW and 45. OkW or less, the refrigerant connecting pipe having an outer diameter of 22.2 mm or less is used.  Air conditioner (1). [5] One or more heat source units (2),  One or more units (4, 5),  A refrigerant communication pipe (6, 7) constituting a refrigerant circuit (10) by connecting the heat source unit and the utilization unit;  In the refrigerant circuit, carbon dioxide is sealed as a refrigerant,  If the rated cooling capacity is greater than 45. OkW and less than or equal to 56. OkW, a pipe with an outer diameter of 25.4 mm or less is used as the refrigerant connection pipe.  Air conditioner (1).  [6] The heat source unit (2) includes a compressor (21), a heat source side heat exchanger (23) capable of cooling the refrigerant compressed by the compressor, and the heat source. The air conditioner (1) according to any one of claims 5 to 6, further comprising an auxiliary cooler (25) capable of further cooling the refrigerant cooled in the side heat exchanger.  [7] The refrigerant communication pipe includes a first refrigerant communication pipe (6) capable of sending the refrigerant cooled in the auxiliary cooler (25) to the utilization unit (4, 5), and the utilization unit. And a second refrigerant communication pipe (7) capable of sending refrigerant to the heat source unit (2) from the compressor (21) to the heat source side heat exchanger (7). 23) and an auxiliary refrigerant circuit capable of returning to the suction side of the compressor after depressurizing a part of the refrigerant flowing between the auxiliary refrigerant (25) and the first refrigerant communication pipe (25) 61)  The auxiliary cooler is a heat exchanger that uses the refrigerant flowing through the auxiliary refrigerant circuit as a cooling source.  The air conditioner (1) according to claim 6. [8] The refrigerant cooled by the heat source side heat exchanger (23) is transferred to the auxiliary cooler (25). The air conditioner (1) according to claim 7, wherein the air conditioner (1) is further cooled by 20 ° C or more.