WO2024023988A1

WO2024023988A1 - Refrigeration cycle device

Info

Publication number: WO2024023988A1
Application number: PCT/JP2022/029005
Authority: WO
Inventors: 智隆石川
Original assignee: 三菱電機株式会社
Priority date: 2022-07-27
Filing date: 2022-07-27
Publication date: 2024-02-01

Abstract

This refrigeration cycle device (1) comprises a load device (3) and an outdoor unit (2). The outdoor unit (2) includes: a first flow path (F1) from a refrigerant inlet port (PI2) to a refrigerant outlet port (PO2); a condenser (20); a plurality of compressors (10A, 10B) disposed in parallel in the first flow path (F1) between the refrigerant inlet port (PI2) and the condenser (20); a liquid receiver (73); a second flow path (F2) that branches from a section of the first flow path (F1) between the condenser (20) and the refrigerant outlet port (PO2) and is connected to the liquid receiver (73); a second expansion valve (71) disposed in the second flow path (F2); a plurality of third flow paths (F3A, F3B) that branch downstream of the liquid receiver (73) and feed a refrigerant to the plurality of compressors (10A, 10B); and a plurality of third expansion valves (72A, 72B) respectively disposed in the plurality of third flow paths (F3A, F3B).

Description

Refrigeration cycle equipment

This invention relates to a refrigeration cycle device.

Some refrigeration cycle devices are designed to reduce the compression ratio per single stage of the compressor by performing compression in two stages. In such refrigeration cycle equipment, by minimizing the refrigerant flow rate in the lower stage cycle, the compression power in the lower stage can be minimized, making it possible to improve efficiency compared to a single stage cycle. becomes.

However, the temperature of the refrigerant supplied to the high-stage compressor may rise, and the degree of superheat of the refrigerant discharged from the high-stage compressor may become excessive. As a countermeasure for this, the refrigeration cycle device disclosed in Japanese Patent Application Laid-Open No. 2020-24046 heats an intermediate pipe that supplies refrigerant discharged from an intermediate receiver to a suction port of a high-stage compressor, and a refrigerant flowing through the intermediate pipe. The system includes an internal heat exchanger, a bypass pipe that supplies the liquid phase refrigerant separated by the gas-liquid separator to the intermediate pipe on the upstream side of the internal heat exchanger, and a control valve provided in the bypass pipe.

By injecting refrigerant into the compressor from the bypass pipe, it is possible to prevent problems with the high-stage compressor caused by the degree of superheat of the refrigerant discharged from the high-stage compressor being too high.

JP2020-24046A

In recent years, the use of natural refrigerants in refrigeration cycle devices has been considered as a measure against global warming. Among natural refrigerants, refrigeration cycle devices that use CO ₂ refrigerant store refrigerant on intermediate piping (hereinafter also referred to as injection flow path) that supplies refrigerant to the suction port (intermediate pressure port) of the high-stage compressor. It is conceivable to place an intermediate pressure receiver below the critical pressure.

However, refrigeration cycle devices are required to have a variety of capacities, from small to large. For example, if a configuration is adopted in which multiple compressors are installed in parallel to increase capacity, multiple injection channels are also required. The intermediate pressure receiver is located on the injection flow path, but since it is a container that requires pressure resistance, the manufacturing cost is high, and it is difficult to install multiple receivers due to the total cost and installation space.

An object of the present disclosure is to provide a refrigeration cycle device that solves such problems and can achieve large capacity while suppressing cost and size.

The refrigeration cycle device of the present disclosure includes a load device including a first expansion valve and an evaporator, and an outdoor unit having a refrigerant outlet port and a refrigerant inlet port for connection to the load device. The outdoor unit includes a first flow path that is a flow path from a refrigerant inlet port to a refrigerant outlet port and forms a circulation flow path in which the refrigerant circulates together with the load device, and a condenser disposed in the first flow path. A plurality of compressors arranged in parallel between the refrigerant inlet port and the condenser in the first flow path, a liquid receiver, and a plurality of compressors arranged in parallel between the refrigerant inlet port and the refrigerant outlet port in the first flow path; , a second flow path connected to the liquid receiver, a second expansion valve disposed in the second flow path, and a plurality of third expansion valves that branch downstream of the liquid receiver and send refrigerant to the plurality of compressors, respectively. It includes a flow path and a plurality of third expansion valves respectively arranged in the plurality of third flow paths.

According to the refrigeration cycle device of the present disclosure, since the number of intermediate pressure liquid receivers is not increased, a large capacity can be achieved while suppressing cost and size.

1 is an overall configuration diagram of a refrigeration cycle device according to Embodiment 1. FIG. 7 is a flowchart for explaining control of the opening degree of the expansion valve 71. FIG. It is a flow chart for explaining control of the opening degree of expansion valve 72A. It is a flow chart for explaining control of the opening degree of expansion valve 72B. It is a flow chart for explaining stop control of a compressor during low capacity operation. FIG. 2 is an overall configuration diagram of a refrigeration cycle device according to a second embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Although a plurality of embodiments will be described below, it has been planned from the beginning of the application to appropriately combine the configurations described in each embodiment. In addition, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is an overall configuration diagram of a refrigeration cycle device according to a first embodiment. Note that FIG. 1 functionally shows the connection relationship and arrangement of each device in the refrigeration cycle apparatus, and does not necessarily show the arrangement in a physical space.

The refrigeration cycle device 1 shown in FIG. 1 includes an outdoor unit 2 and a load device 3. The outdoor unit 2 has a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connection to the load device 3. The load device 3 has a refrigerant outlet port PO3 and a refrigerant inlet port PI3 for connection to the outdoor unit 2.

The outdoor unit 2 of the refrigeration cycle device 1 is configured so that it can be connected to a load device 3 via an extension pipe or the like. The outdoor unit 2 includes an accumulator 60,

compressors

10A and 10B, a condenser 20, and

heat exchangers

30A and 30B.

Each of the

compressors

10A and 10B is a single-stage compressor having a suction port, a discharge port, and an injection port. Each of the

heat exchangers

30A, 30B has a first passage and a second passage, and is configured to exchange heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage.

The load device 3 includes a first expansion valve 40 and an evaporator 50. Evaporator 50 is configured to exchange heat between air and refrigerant. In the refrigeration cycle device 1, the evaporator 50 evaporates the refrigerant by absorbing heat from the air in the space to be cooled. The first expansion valve 40 is, for example, a temperature expansion valve that is controlled independently of the outdoor unit 2. Note that the first expansion valve 40 may be an electronic expansion valve that can reduce the pressure of the refrigerant.

The compressor 10A compresses the refrigerant sucked from the accumulator 60 via the pipe 86A and discharges it to the pipe 80A. Compressor 10B compresses the refrigerant sucked from accumulator 60 via piping 86B and discharges it to piping 80B. The

pipes

80A and 80B join to form a pipe 80, which is connected to the condenser 20. Each of the

compressors

10A and 10B is configured so that its operating frequency can be changed within a predetermined range by inverter control. Further, each of the

compressors

10A and 10B is provided with an injection port, and the refrigerant from the injection port can be made to flow into the middle part of the compression process.

Compressors

10A and 10B are configured to adjust their rotational speeds according to control signals from control device 100. By adjusting the rotational speeds of the

compressors

10A and 10B, the amount of refrigerant circulated can be adjusted, and the capacity of the refrigeration cycle device 1 can be adjusted. Various types of compressors can be used for the

compressors

10A and 10B, and for example, a scroll type can be used.

The condenser 20 is configured so that the high temperature, high pressure gas refrigerant discharged from the

compressors

10A and 10B exchanges heat (radiates heat) with the outside air. This heat exchange causes the refrigerant to condense and change into a liquid phase. The refrigerant discharged from the

compressors

10A and 10B into the pipe 80 is condensed and liquefied in the condenser 20 and flows out into the pipe 81. A fan (not shown) is attached to the condenser 20 to send outside air to increase the efficiency of heat exchange.

Here, the refrigerant used in the refrigerant circuit of the refrigeration cycle device 1 is CO ₂ , but if a situation arises in which it is difficult to ensure the degree of supercooling, other refrigerants may be used.

In this specification, for ease of explanation, the condenser 20 will also be referred to when cooling a refrigerant such as CO ₂ in a supercritical state. Furthermore, in this specification, for ease of explanation, the amount of decrease from the reference temperature of the refrigerant in the supercritical state will also be referred to as the degree of supercooling.

The pipe 81 branches into

pipes

81A and 81B. The refrigerant that has passed through the

pipes

81A and 81B flows out into the

pipes

82A and 82B after passing through the first flow paths of the

heat exchangers

30A and 30B, respectively. The

pipes

82A and 82B merge to form a pipe 82.

A first flow path F1 from the refrigerant inlet port PI2 to the refrigerant outlet port PO2 via each first path of the

compressors

10A, 10B, the condenser 20, and the

heat exchangers

30A, 30B is a first expansion path of the load device 3. Together with the flow path in which the valve 40 and the evaporator 50 are arranged, a circulation flow path through which the refrigerant circulates is formed. Hereinafter, this circulation flow path will also be referred to as the "main refrigerant circuit" of the refrigeration cycle.

The outdoor unit 2 further includes a second expansion valve 71, an intermediate receiver (liquid receiver) 73, on-off

valves

70A, 70B, and

third expansion valves

72A, 72B.

A pipe 91 branches from the boundary between the pipe 82 and the pipe 83 and is connected to the second expansion valve 71. The second expansion valve 71 and the intermediate pressure receiver 73 are connected by a pipe 92.

Pipes

91 and 92 constitute a second flow path F2. A pipe 93 for discharging liquid refrigerant is connected to the bottom of the intermediate pressure receiver 73. The pipe 93 branches into

pipes

93A and 93B. The liquid refrigerant stored at the bottom of the intermediate pressure receiver 73 passes through the

pipes

93A and 93B, respectively, and is depressurized at the

third expansion valves

72A and 72B. The refrigerant whose pressure has been reduced in the

third expansion valves

72A, 72B passes through the

pipes

94A, 94B, respectively, and is sent to the second passages of the

heat exchangers

30A, 30B. The refrigerant that has passed through each of the second passages of

heat exchangers

30A and 30B further passes through piping 95A and 95B, respectively, and is sent to each injection port of

compressor

10A and 10B.

The

pipes

91 and 92 constitute a second flow path F2, the

pipes

93A, 94A, and 95A constitute a third flow path F3A, and the

pipes

93B, 94B, and 95B constitute a third flow path F3B.

In the following, channels F2, F3A, and F3B that branch from the main refrigerant circuit and send refrigerant to the injection ports of the

compressors

10A and 10B via the second channels of the

heat exchangers

30A and 30B are referred to as "injection flows". Also called "road".

The intermediate pressure receiver 73 is disposed in common to the flow paths F3A and F3B and stores refrigerant. The on-off valve 70A opens and closes a gas vent passage that communicates the gas exhaust port of the intermediate pressure receiver 73 with the connecting portion of the piping 94A and the piping 95A. The on-off valve 70B opens and closes a gas vent passage that communicates the gas exhaust port of the intermediate pressure receiver 73 with the connecting portion of the piping 94B and the piping 95B. The expansion valve 72A adjusts the refrigerant flow rate in the flow path F3A. The expansion valve 72B adjusts the refrigerant flow rate in the flow path F3B.

The second expansion valve 71 is an electronic expansion valve that can reduce the refrigerant in the high pressure section of the main refrigerant circuit to an intermediate pressure. The intermediate pressure receiver 73 is a container that separates the gas phase and liquid phase of the refrigerant that has been reduced in pressure into two phases within the container, stores the liquid refrigerant, and can adjust the amount of refrigerant circulation in the main refrigerant circuit. . A gas venting pipe connected to the upper part of the intermediate pressure receiver 73 and a pipe 93 connected to the lower part of the intermediate pressure receiver 73 take out the refrigerant separated into gas refrigerant and liquid refrigerant in the intermediate pressure receiver 73 in a separated state. This is the piping for this purpose. The amount of refrigerant in the intermediate pressure receiver 73 can be adjusted by adjusting the amount of liquid refrigerant discharged from the pipe 93 using the

third expansion valves

72A and 72B.

By providing the intermediate pressure receiver 73 in the injection flow path in this way, it becomes easy to ensure the degree of supercooling of the refrigerant in the pipe 83, which is a liquid pipe. Generally, since gas refrigerant is present in the intermediate pressure receiver 73, the refrigerant temperature becomes the saturation temperature. Therefore, if the intermediate pressure receiver 73 is disposed in the

pipes

82 and 83 without intervening the second expansion valve 71, the degree of subcooling of the refrigerant This is because it cannot be ensured.

Furthermore, by providing the intermediate pressure receiver 73 in the intermediate pressure section, even when the pressure in the high pressure section of the main refrigerant circuit is high and the refrigerant is in a supercritical state, intermediate pressure liquid refrigerant can be stored inside the intermediate pressure receiver 73. It becomes possible. Therefore, the design pressure of the container of the intermediate pressure receiver 73 can be lower than that of the high pressure section.

The outdoor unit 2 further includes a pressure sensor 111,

temperature sensors

120A, 120B, 121, and a control device 100. The control device 100 is configured to control the

compressors

10A, 10B, the second expansion valve 71, and the

third expansion valves

72A, 72B.

The pressure sensor 111 detects the pressure PH of the refrigerant in the pipe 80 discharged from the

compressors

10A and 10B and merged together, and outputs the detected value to the control device 100.

The temperature sensor 120A detects the discharge temperature TdA of the compressor 10A and outputs the detected value to the control device 100. Temperature sensor 120B detects the discharge temperature TdB of compressor 10B and outputs the detected value to control device 100. The temperature sensor 121 detects the refrigerant temperature T1 of the pipe 81 at the outlet of the condenser 20 and outputs the detected value to the control device 100.

In the present embodiment, the flow path F2 controls the discharge temperatures TdA and TdB of the

compressors

10A and 10B by causing the refrigerant that has been reduced in pressure to become two-phase to flow into the

compressors

10A and 10B. In addition, the amount of refrigerant in the main refrigerant circuit can be adjusted by the intermediate pressure receiver 73 installed on the flow path F2. Furthermore, the second flow path F2 is also responsible for ensuring supercooling of the refrigerant in the main refrigerant circuit through heat exchange by the

heat exchangers

30A and 30B.

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown) for inputting and outputting various signals, etc. It consists of: The CPU 102 expands the program stored in the ROM into a RAM or the like and executes the program. The program stored in the ROM is a program in which the processing procedure of the control device 100 is written. The control device 100 executes control of each device in the outdoor unit 2 according to these programs. This control is not limited to processing by software, but can also be performed by dedicated hardware (electronic circuit).

As shown in the configuration of FIG. 1, in a refrigeration cycle device 1 in which an intermediate pressure receiver 73 is installed in the injection flow path and

compressors

10A and 10B are configured in parallel, gas and liquid are separated by the intermediate pressure receiver 73 provided in common. The liquid refrigerant is branched and distributed through flow paths F3A and F3B of the

compressors

10A and 10B, respectively. With such a configuration, the branching portions to the injection channels F3A and F3B to each compressor are reliably liquid single-phase, so it is possible to avoid uneven distribution of liquid refrigerant/gas refrigerant.

Next, the control executed by the control device 100 will be explained using a flowchart.
FIG. 2 is a flowchart for explaining control of the opening degree of the expansion valve 71. First, in step S1, the control device 100 detects the degree of subcooling SC of the refrigerant by referring to a table prepared in advance based on the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure (approximated by PH) of the condenser 20. do.

Subsequently, in step S2, the control device 100 compares the degree of supercooling SC and the target degree of supercooling SC*. When the degree of supercooling SC is larger than the target degree of supercooling SC* (YES in S2), the control device 100 reduces the opening degree of the expansion valve 71 (S3). As a result, the amount of liquid refrigerant flowing into the intermediate pressure receiver 73 decreases, and the amount of liquid refrigerant inside the intermediate pressure receiver 73 decreases, so the amount of refrigerant circulating through the main refrigerant circuit increases. Thereby, when the amount of heat dissipated from the condenser 20 is constant, the degree of supercooling SC decreases.

On the other hand, if the degree of supercooling SC is equal to or less than the target degree of supercooling SC* (NO in S2), the control device 100 increases the opening degree of the expansion valve 71 (S4). As a result, the amount of liquid refrigerant flowing into the intermediate pressure receiver 73 increases, the amount of liquid refrigerant stored in the intermediate pressure receiver 73 increases, and the amount of refrigerant circulating through the main refrigerant circuit decreases. Thereby, when the amount of heat dissipated from the condenser 20 is constant, the degree of supercooling SC increases.

In this way, the control device 100 controls the opening degree of the second expansion valve 72 so that the degree of subcooling SC of the refrigerant at the outlet of the condenser 20 approaches the target degree of subcooling SC*.

FIG. 3 is a flowchart for explaining control of the opening degree of the expansion valve 72A. First, in step S11, the control device 100 detects the temperature TdA of the refrigerant discharged by the compressor 10A using the temperature sensor 120A.

Subsequently, in step S12, the control device 100 compares the temperature TdA and the target temperature TdA*. If the temperature TdA is higher than the target temperature TdA* (YES in S12), the control device 100 increases the opening degree of the expansion valve 72A (S13). As a result, the amount of intermediate pressure refrigerant introduced into the compressor 100A increases, and the discharge temperature TdA of the compressor 100A decreases.

On the other hand, if the temperature TdA is lower than the target temperature TdA* (NO in S12), the control device 100 reduces the opening degree of the expansion valve 72A (S14). As a result, the amount of intermediate pressure refrigerant introduced into the compressor 100A decreases, and the discharge temperature TdA of the compressor 100A increases.

In this way, the control device 100 controls the opening degree of the expansion valve 72A so that the discharge temperature TdA of the compressor 10A approaches the target temperature TdA*.

FIG. 4 is a flowchart for explaining control of the opening degree of the expansion valve 72B. First, in step S21, the control device 100 detects the temperature TdB of the refrigerant discharged by the compressor 10B using the temperature sensor 120B.

Subsequently, in step S22, the control device 100 compares the temperature TdB and the target temperature TdB*. If the temperature TdB is higher than the target temperature TdB* (YES in S22), the control device 100 increases the opening degree of the expansion valve 72B (S23). As a result, the amount of intermediate pressure refrigerant introduced into the compressor 100B increases, and the discharge temperature TdB of the compressor 100B decreases.

On the other hand, if the temperature TdB is lower than the target temperature TdB* (NO in S22), the control device 100 reduces the opening degree of the expansion valve 72B (S24). As a result, the amount of intermediate pressure refrigerant introduced into the compressor 100B is reduced, and the discharge temperature TdB of the compressor 100B is increased.

In this way, the control device 100 controls the opening degree of the expansion valve 72B so that the discharge temperature TdB of the compressor 10B approaches the target temperature TdB*.

By repeatedly performing the processes in FIGS. 2 to 4, the amount of refrigerant circulating in the main refrigerant circuit and the discharge temperatures TdA and TdB of the

compressors

10A and 10B can be set to appropriate values.

(Control during low capacity operation)
The refrigeration cycle device 1 shown in FIG. 1 has a plurality of compressors connected in parallel to increase capacity.

If the load is large, multiple compressors can be operated at the same time, but depending on the season, the load may drop and low-capacity operation may be necessary. In such a case, if multiple compressors are operated at the same time, the frequency of turning the compressors on and off will increase, so some of the compressors may be stopped and one compressor may be operated to reduce the capacity. and continuous operation.

However, when operating in this way, if the same compressor is always stopped, the operating time will be uneven and the overall product life will be shortened. Therefore, when shifting to low capacity operation, the stop history is checked and the operating time is averaged so as not to fix the compressor to be stopped among the plurality of compressors.

FIG. 5 is a flowchart for explaining compressor stop control during low capacity operation. First, in step S31, the control device 100 determines whether to shift to low capacity operation. For example, in the case of a refrigeration system, the control device 100 determines to shift to low-capacity operation when the internal temperature falls too much below a set temperature.

If there is no transition to low capacity operation (NO in S31), the process exits from the control shown in the flowchart of FIG. On the other hand, when shifting to low capacity operation (YES in S31), the control device 100 reads out previous compressor stop history information from a nonvolatile memory or the like in step S32. For example, if there are two compressors as shown in Figure 1, remembering which compressor was stopped during the previous low-capacity operation can be used as a reference when deciding which compressor to stop this time. can do.

Subsequently, in step S33, the control device 100 determines the compressor to be stopped. Specifically, the compressor that was stopped during the previous low capacity operation is operated this time, and the compressor that was operated during the previous low capacity operation is stopped this time. As a result, the total operating time of each of the two compressors is averaged because the stops are performed alternately. When the compressor is stopped, the injection flow path is also shut off by closing the

expansion valves

72A, 72B and on-off

valves

70A, 70B that correspond to the stopped compressor.

Then, in step S34, the control device 100 updates the stop history information to reflect the result determined in step S33, and stores it in a nonvolatile memory or the like.

As described above, the compressor to be stopped is determined when transitioning to low capacity operation.
In addition, when there are two compressors, they are stopped alternately, but when there are three or more compressors, the compressor with the least number of stops is stopped so that the number of stops is averaged. Just do it.

In addition, if the total operating time is also stored in the stop history information and the compressor with the longest total operating time is stopped in step S33, even if the operating time of low capacity operation is longer or shorter, , it is possible to accurately optimize the service life.

Embodiment 2.
FIG. 6 is an overall configuration diagram of a refrigeration cycle device according to the second embodiment. Note that FIG. 6 functionally shows the connection relationship and arrangement of each device in the refrigeration cycle apparatus, and does not necessarily show the arrangement in a physical space.

A refrigeration cycle device 201 shown in FIG. 6 includes an outdoor unit 202 and a load device 3. The outdoor unit 202 has a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connection to the load device 3. The load device 3 has a refrigerant outlet port PO3 and a refrigerant inlet port PI3 for connection to the outdoor unit 2. The configuration of the load device 3 is the same as the load device shown in FIG.

The outdoor unit 202 includes compressors 210A and 210B in place of the

compressors

10A and 10B in the configuration of the outdoor unit 2 shown in FIG. The configuration of other parts of the outdoor unit 202 is similar to the configuration of the outdoor unit 2, so the description will not be repeated here.

The

compressors

10A and 10B were single-stage compressors with injection ports, but the compressors 210A and 210B were two-stage compressors with intermediate pressure ports.

The compressor 210A includes a first stage compressor 211A, an intercooler 121A, and a second stage compressor 213A. Compressor 210B includes a first-stage compressor 211B, an intercooler 121B, and a second-stage compressor 213B.

In the second embodiment, various types of compressors 210A and 210B can be used, such as scroll type, rotary type, screw type, etc.

The configuration in FIG. 6 is also similar to the configuration in FIG. 1 in that a plurality of compressors 210A and 210B operate in parallel in the flow path F1 of the main refrigerant circuit. In the flow path F1, the refrigerant flows in the order of first-

stage compressors

211A and 211B,

intercoolers

212A and 212B, and second-

stage compressors

213A and 213B. Thereafter, the combined refrigerants flow through the condenser 20,

heat exchangers

30A, 30B, expansion valve 40, evaporator 50, and accumulator 60 in this order, and return to the first-

stage compressors

211A, 211B.

By cooling the refrigerant in the

intercoolers

212A and 212B and merging the injection flow paths therewith, the compression power of the

downstream compressors

213A and 213B can be lowered, resulting in an energy saving effect.

Intercoolers

212A and 212B may be integrated with condenser 20.

In the injection flow path F2, the refrigerant that has passed through the expansion valve 71 and the intermediate pressure receiver 73 is branched and the flow rate is adjusted by the

expansion valves

72A and 72B. It is sucked into the

compressors

213A and 213B in the first stage.

In the second embodiment, as in the first embodiment, a large-capacity refrigeration cycle device can be realized by operating multiple existing compressors in parallel without increasing the number of intermediate pressure receivers 73, which are pressure-resistant containers. . Therefore, manufacturing costs and development man-hours can be reduced.

(summary)
Embodiments 1 and 2 will be summarized below with reference to the drawings again.

(1) The

refrigeration cycle device

1, 201 shown in FIGS. 1 and 6 includes a load device 3 including a first expansion valve 40 and an evaporator 50, and a refrigerant outlet port PO2 and a refrigerant inlet port for connecting to the load device 3. and an outdoor unit 2 having a PI2. The outdoor unit 2 is arranged in a first flow path F1, which is a flow path from the refrigerant inlet port PI2 to the refrigerant outlet port PO2, and forms a circulation flow path in which the refrigerant circulates together with the load device 3. a plurality of

compressors

10A, 10B or 210A, 210B arranged in parallel between the refrigerant inlet port PI2 and the condenser 20 in the first flow path F1, an intermediate pressure receiver 73, A second flow path F2 that branches from a portion of the first flow path F1 between the condenser 20 and the refrigerant outlet port PO2 and is connected to the intermediate pressure receiver 73, and a second expansion valve disposed in the second flow path F2. 71, a plurality of third flow paths F3A, F3B that branch downstream of the intermediate pressure receiver 73 and send refrigerant to the plurality of

compressors

10A, 10B or 210A, 210B, respectively, and a plurality of third flow paths F3A, F3B. A plurality of

third expansion valves

72A and 72B are provided.

(2) In item (1), the outdoor unit 2 is provided between the plurality of

third expansion valves

72A, 72B and the plurality of

compressors

10A, 10B or 210A, 210B in the plurality of third flow paths F3A, F3B, respectively. It further includes a plurality of

heat exchangers

30A and 30B arranged. Each of the plurality of heat exchangers 30A, 30B connects the refrigerant flowing through the corresponding third flow path F3A, F3B to the branch point where the second flow path F2 branches after passing through the condenser 20 in the first flow path F1. It is configured to exchange heat with the oncoming refrigerant.

(3) In (1) or (2), the outdoor unit 2 further includes a control device 100 configured to control the second expansion valve 71 and the plurality of

third expansion valves

72A, 72B. The control device 100 controls the opening degree of the second expansion valve 71 based on the degree of subcooling SC of the refrigerant at the outlet of the condenser 20, and controls the opening degree of each of the plurality of

third expansion valves

72A, 72B based on the degree of subcooling SC of the refrigerant at the outlet of the condenser 20. It is configured to control based on the discharge temperature of the

compressors

10A, 10B or 210A, 210B corresponding to each of the

third expansion valves

72A, 72B.

(4) In item (1), as shown in FIG. 1, each of the plurality of

compressors

10A and 10B is a single-stage compressor with an injection port, and the plurality of third flow paths F3A and F3B are Each is connected to a corresponding injection port.

(5) In item (1), as shown in FIG. 211A and an intermediate pressure port that communicates with intermediate portions of 213A, 211B, and 213B, and each of the plurality of third flow paths F3A and F3B is connected to the corresponding intermediate pressure port.

(6) In item (1), the outdoor unit 2 further includes a control device 100 configured to control the plurality of

compressors

10A, 10B or 210A, 210B. As shown in FIG. 5, when the refrigeration load is lower than the determination value (YES in S31), the control device 100 stops a part of the plurality of

compressors

10A, 10B or 210A, 210B, and is configured to perform low load operation. The control device is configured to determine which compressor to stop each time low load operation occurs so that the operating times of the plurality of

compressors

10A, 10B or 210A, 210B are not uneven (S33). .

In the refrigeration cycle apparatuses of

Embodiments

1 and 2 described above, the following effects can be obtained.

Increasing the capacity of one compressor requires new development and new parts, which requires a lot of man-hours and costs. On the other hand, in the refrigeration cycle apparatuses of

Embodiments

1 and 2, the capacity can be freely expanded by adding the number of existing compressors, and new parts for the compressors are not required.

Note that the intermediate pressure receiver 73 is effective when the refrigerant uses supercriticality such as _CO2 . Since the intermediate pressure receiver 73 is shared by a plurality of compressors, it is possible to realize an outdoor unit with a compact size. Furthermore, costs can be reduced if the receiver, which is a pressure vessel, is integrated into one.

Furthermore, since

heat exchangers

30A and 30B are installed to exchange heat between the refrigerant at the outlet of the condenser 20 and the refrigerant passing through the injection channels F3A and F3B, the performance of the refrigeration cycle device can be improved. .

Furthermore, by branching the single-phase liquid stored in the intermediate pressure receiver 73 into the two injection channels F3A and F3B, it is possible to avoid imbalance in liquid/gas distribution, which would be a concern if branching into two phases. . Thereby, the heat exchange amount of each of the

heat exchangers

30A and 30B can be reliably obtained, and the controllability of the discharge temperature in each compressor is stabilized.

Furthermore, since a gas vent pipe is installed in the intermediate pressure receiver 73, controllability of the amount of refrigerant stored is improved.

Further, since the suction portions of each compressor are branched at the common accumulator 60, the refrigerant liquid and refrigerating machine oil are preferably evenly distributed to the plurality of

compressors

10A, 10B or 210A, 210B.

Although the present embodiment has been described above by exemplifying the case where the

refrigeration cycle device

1, 201 is mainly applied to a refrigerator, the

refrigeration cycle device

1, 201 may also be used in an air conditioner or the like.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the description of the embodiments described above, and it is intended that equivalent meanings and all changes within the scope of the claims are included.

1,201 Refrigeration cycle device, 2,202 Outdoor unit, 3 Load device, 10A, 10B, 100A, 100B, 210A, 210B, 211A, 211B, 213A, 213B Compressor, 20 Condenser, 30A, 30B Heat exchanger, 40, 71, 72A, 72B expansion valve, 50 evaporator, 60 accumulator, 70A, 70B on-off valve, 73 intermediate pressure receiver, 100 control device, 102 CPU, 104 memory, 111 pressure sensor, 120A, 120B, 121 temperature sensor, 121A, 121B, 212A, 212B intercooler, F1, F2, F3B, F3A flow path, PI2, PI3 refrigerant inlet port, PO2, PO3 refrigerant outlet port.

Claims

a load device including a first expansion valve and an evaporator;
an outdoor unit having a refrigerant outlet port and a refrigerant inlet port for connection with the load device, the outdoor unit comprising:
a first flow path that extends from the refrigerant inlet port to the refrigerant outlet port and forms a circulation flow path in which the refrigerant circulates together with the load device;
a condenser disposed in the first flow path;
a plurality of compressors arranged in parallel between the refrigerant inlet port and the condenser in the first flow path;
a liquid receiver;
a second flow path branching from a portion of the first flow path between the condenser and the refrigerant outlet port and connected to the liquid receiver;
a second expansion valve disposed in the second flow path;
a plurality of third flow paths that branch downstream of the liquid receiver and send refrigerant to the plurality of compressors, respectively;
A refrigeration cycle device comprising: a plurality of third expansion valves respectively arranged in the plurality of third flow paths.
The outdoor unit further includes a plurality of heat exchangers arranged between the plurality of third expansion valves and the plurality of compressors in the plurality of third flow paths,
Each of the plurality of heat exchangers is arranged between the refrigerant flowing through the corresponding third flow path and the refrigerant passing through the condenser in the first flow path and heading toward a branch point where the second flow path branches. The refrigeration cycle device according to claim 1, configured to exchange heat with.
The outdoor unit further includes a control device configured to control the second expansion valve and the plurality of third expansion valves,
The control device controls the opening degree of the second expansion valve based on the degree of subcooling of the refrigerant at the outlet of the condenser, and controls the opening degree of each of the plurality of third expansion valves based on the degree of subcooling of the refrigerant at the outlet of the condenser. The refrigeration cycle device according to claim 1 or 2, wherein the refrigeration cycle device is configured to perform control based on the discharge temperature of the compressor corresponding to each of the expansion valves.
Each of the plurality of compressors is a single-stage compressor having an injection port,
The refrigeration cycle device according to claim 1, wherein each of the plurality of third flow paths is connected to a corresponding injection port.
Each of the plurality of compressors is
A two-stage compressor connected in series,
an intermediate pressure port communicating with an intermediate portion of the two-stage compressor;
The refrigeration cycle apparatus according to claim 1, wherein each of the plurality of third flow paths is connected to a corresponding intermediate pressure port.
The outdoor unit further includes a control device configured to control the plurality of compressors,
The control device is configured to execute a low-load operation in which a part of the plurality of compressors is stopped and the remaining compressors are operated when the refrigeration load is lower than a determination value,
The controller according to claim 1, wherein the control device is configured to determine which compressor to stop each time the low-load operation occurs so that the operating times of the plurality of compressors are not uneven. Refrigeration cycle equipment.