Refrigeration cycle device

Abstract

A refrigeration cycle device (1) is provided with a first circuit (10), a second circuit (20), and a control unit (6). The first circuit (10) comprises a first compressor (11), a first heat exchanger (12), a first expansion mechanism (13) and a cascade heat exchanger (30). The first circuit (10) circulates a first refrigerant. The second circuit (20) comprises a second compressor (21), a second heat exchanger (23), a cascade heat exchanger (30), a second expansion mechanism (24) and a third heat exchanger (25). A second circuit (20) circulates a second refrigerant. The control unit (6) performs stop control in which the first refrigerant is concentrated in the first heat exchanger (12) before the operation of the first circuit (10) is stopped.

Description

Technical Field

[0001] This disclosure relates to a refrigeration cycle apparatus. Background Technology

[0002] Patent document 1 (Japanese Patent No. 5430604) discloses a binary refrigeration device including a low-level refrigeration cycle using carbon dioxide refrigerant and a high-level refrigeration cycle that assists in the heat dissipation of the low-level refrigeration cycle. In this binary refrigeration device, the evaporator of the high-level refrigeration cycle and the condenser of the low-level refrigeration cycle exchange heat through cascaded capacitors. Summary of the Invention

[0003] The technical problem that the invention aims to solve

[0004] However, the inventors focused on the problem that liquid refrigerant might flow into the compressor in the binary refrigeration apparatus of Patent Document 1.

[0005] Technical solutions adopted to solve technical problems

[0006] The inventors discovered that the aforementioned problem arises because, when the Takamoto refrigeration cycle stops, the evaporator of the Takamoto refrigeration cycle in the cascaded capacitor is cooled, causing the refrigerant to liquefy. In this state, when the Takamoto refrigeration cycle is operated, the liquefied refrigerant flows into the compressor.

[0007] Therefore, the first-view refrigeration cycle device includes a first loop, a second loop, and a control unit. The first loop includes a first compressor, a first heat exchanger, a first expansion mechanism, and a cascaded heat exchanger. The first loop supplies a first refrigerant. The second loop includes a second compressor, a second heat exchanger, a cascaded heat exchanger, a second expansion mechanism, and a third heat exchanger. The second loop supplies a second refrigerant. The control unit performs stop control by concentrating the first refrigerant into the first heat exchanger before stopping the operation of the first loop.

[0008] In the refrigeration cycle apparatus of the first viewpoint, the control unit performs stop control to concentrate the first refrigerant into the first heat exchanger before stopping the operation of the first circuit, thus reducing the amount of first refrigerant concentrated in the cascade heat exchanger. Therefore, liquefaction of the first refrigerant within the cascade heat exchanger can be suppressed during the shutdown of the first circuit. Operating the first circuit in this state further prevents the liquefied first refrigerant from flowing into the first compressor.

[0009] The second viewpoint refrigeration cycle device is based on the first viewpoint refrigeration cycle device, in which the control unit operates the second circuit before the first circuit operates during refrigeration operation.

[0010] In the second viewpoint's refrigeration cycle apparatus, the second circuit is operated before the first circuit. This allows the second refrigerant, after passing through the second heat exchanger in the second circuit, to transfer heat to the first refrigerant concentrated in the cascade heat exchanger as it passes through the cascade heat exchanger. This heat can then be used to heat the first refrigerant, thereby further preventing the liquefied first refrigerant from flowing into the first compressor.

[0011] The third viewpoint's refrigeration cycle device is based on the second viewpoint's refrigeration cycle device. When the difference between the inlet temperature and the outlet temperature of the cascaded heat exchanger in the second loop reaches a specified value or below, the first loop starts operating.

[0012] In the third viewpoint of the refrigeration cycle device, when the difference between the inlet and outlet temperatures of the cascaded heat exchanger in the second loop falls below a predetermined value, it is determined that heat from the second refrigerant has been transferred to the first refrigerant in the cascaded heat exchanger, causing the first refrigerant to vaporize. Under this condition, the first loop operates, thus further preventing the liquefied first refrigerant from flowing into the first compressor.

[0013] The fourth viewpoint's refrigeration cycle device is based on the second viewpoint's refrigeration cycle device, in which the control unit starts the operation of the first circuit after a predetermined time has elapsed since the start of the second circuit's operation.

[0014] In the fourth viewpoint of the refrigeration cycle device, after a predetermined time has elapsed since the start of operation of the second loop, it is determined that the heat of the second refrigerant has been transferred to the first refrigerant in the cascaded heat exchanger, resulting in the vaporization of the first refrigerant. Under this state, operation of the first loop is performed, thereby further preventing the liquefied first refrigerant from flowing into the first compressor.

[0015] The refrigeration cycle device of the fifth viewpoint is based on the refrigeration cycle device of any of the first to fourth viewpoints, except that the opening of the first expansion mechanism is increased after the first compressor is started.

[0016] In the refrigeration cycle device of the fifth viewpoint, the opening degree of the first expansion mechanism is not increased when the first compressor starts, thus preventing the first refrigerant in the first circuit from directly flowing into the first compressor. Therefore, it is possible to further prevent the liquefied first refrigerant from flowing into the first compressor.

[0017] The refrigeration cycle device of the sixth viewpoint is based on the refrigeration cycle device of the fifth viewpoint. The control unit starts the second compressor, then increases the opening of the second expansion mechanism, then starts the first compressor, and then increases the opening of the first expansion mechanism.

[0018] By controlling the refrigeration cycle device in the order of the second compressor, the second expansion mechanism, the first compressor, and the first expansion mechanism, as in the sixth viewpoint, the first and second circuits can be operated while suppressing the flow of the liquefied first refrigerant into the first compressor.

[0019] The refrigeration cycle device of the seventh viewpoint is based on the refrigeration cycle device of any of the first to sixth viewpoints, and the control unit controls the operation of the first loop and the operation of the second loop.

[0020] Alternatively, as in the refrigeration cycle device of the seventh viewpoint, the control unit of the second loop can control the first loop.

[0021] The refrigeration cycle device of the eighth viewpoint is based on the refrigeration cycle device of any of the first to seventh viewpoints, and the first heat exchanger is a flat porous tube.

[0022] In the refrigeration cycle apparatus of the eighth viewpoint, the flat porous tube serving as the first heat exchanger can reduce its volume, thereby reducing the amount of first refrigerant. Therefore, the amount of first refrigerant concentrated in the cascaded heat exchanger can be reduced.

[0023] The refrigeration cycle device of the ninth viewpoint is based on the refrigeration cycle device of any of the first to eighth viewpoints, and further includes a fan that delivers outdoor air to the first heat exchanger and the second heat exchanger.

[0024] In the refrigeration cycle device of the ninth viewpoint, the fans supplying outdoor air to the first and second heat exchangers are shared. Therefore, even if the first circuit is stopped, outdoor air flows to the first heat exchanger while the second circuit is running. Consequently, the first refrigerant concentrated in the first heat exchanger exchanges heat with the outdoor air, thus facilitating the concentration of the liquefied first refrigerant in the first heat exchanger. This further suppresses the flow of the liquefied first refrigerant into the first compressor.

[0025] The refrigeration cycle device of the tenth viewpoint is based on the refrigeration cycle device of any of the first to ninth viewpoints, and the first loop also includes a storage tank.

[0026] In the refrigeration cycle device of the tenth viewpoint, the liquefied first refrigerant can be stored in a storage tank, thereby further preventing the liquefied first refrigerant from flowing into the first compressor.

[0027] The refrigeration cycle device of the eleventh viewpoint is based on the refrigeration cycle device of any of the first to tenth viewpoints. When the second circuit is in operation and the first circuit is stopped, the control unit sets the first expansion mechanism to be fully closed.

[0028] When the second circuit is operating and the first circuit is stopped, the first refrigerant is easily cooled in the cascaded heat exchanger. In this case, in the refrigeration cycle device of the eleventh viewpoint, by setting the first expansion mechanism to be fully closed, the inflow of the first refrigerant into the cascaded heat exchanger can be reduced. Therefore, it is possible to further suppress the inflow of the liquefied first refrigerant into the first compressor.

[0029] The refrigeration cycle unit of the twelfth viewpoint is based on the refrigeration cycle unit of any of the first to eleventh viewpoints, with the control unit performing heating and cooling operations.

[0030] In the refrigeration cycle unit of the twelfth viewpoint, when the first loop is stopped during heating operation, the first refrigerant concentrated in the cascade heat exchanger is prone to liquefaction, thus easily leading to the problem of liquefied first refrigerant flowing into the first compressor. Even in the case where this problem is likely to occur, the flow of liquefied first refrigerant into the first compressor can be prevented by performing stop control.

[0031] The refrigeration cycle device of the thirteenth viewpoint is based on the refrigeration cycle device of any of the first to twelfth viewpoints, wherein the first refrigerant is flammable, toxic, or has a GWP (global warming factor) exceeding 500.

[0032] Alternatively, as in the refrigeration cycle unit of viewpoint 13, a first refrigerant that is flammable, toxic, or has a GWP exceeding 500 can be used. Attached Figure Description

[0033] Figure 1 This is a schematic structural diagram of a refrigeration cycle apparatus according to one embodiment of the present disclosure.

[0034] Figure 2 This is a sectional view of the outdoor unit.

[0035] Figure 3 This is a schematic three-dimensional diagram of the first heat exchanger.

[0036] Figure 4 This is a control block diagram of a refrigeration cycle unit.

[0037] Figure 5 This is a diagram showing the operation of the refrigeration cycle unit during heating.

[0038] Figure 6 This is a diagram illustrating the operation of a refrigeration cycle unit during refrigeration.

[0039] Figure 7 This is a flowchart for stop control.

[0040] Figure 8 This is the flowchart for starting control.

[0041] Figure 9 This is the flowchart for the start control of Variation Example 1. Detailed Implementation

[0042] (1) Overall structure

[0043] like Figure 1 As shown, the refrigeration cycle apparatus 1 of one embodiment of the present disclosure is an apparatus for cooling and heating indoors such as buildings by performing a vapor compression refrigeration cycle operation.

[0044] The refrigeration cycle device 1 includes a first circuit 10, a second circuit 20, and a control unit 6. The refrigeration cycle device 1 of this embodiment has a binary refrigerant circuit consisting of a vapor compression type first circuit 10 and a vapor compression type second circuit 20, and performs a binary refrigeration cycle.

[0045] The first loop 10 supplies the first refrigerant cycle. The second loop 20 supplies the second refrigerant cycle. The first loop 10 and the second loop 20 are thermally connected via a cascaded heat exchanger 30.

[0046] The refrigeration circulation unit 1 includes an outdoor unit 2 and an indoor unit 3. The refrigeration circulation unit 1 is configured such that the outdoor unit 2 and the indoor unit 3 are interconnected via connecting pipes 4 and 5.

[0047] The control unit 6 performs a stop control, in which the first refrigerant is concentrated into the first heat exchanger 12 before the operation of the first circuit 10 is stopped.

[0048] (2) Detailed structure

[0049] (2-1) First circuit

[0050] The first refrigerant flowing in the first circuit 10 is not particularly limited, but here, the first refrigerant is flammable, toxic, or has a GWP exceeding 500. The first refrigerant is, for example, a hydrocarbon refrigerant, R1234yf, R1234ze, R32, etc., and in this embodiment, it is R290.

[0051] The first circuit 10 constitutes the subcooling circuit during refrigeration operation. The first circuit is an auxiliary circuit that assists the capacity of the second circuit 20 during refrigeration operation.

[0052] The first circuit 10 includes a first compressor 11, a first heat exchanger 12, a first expansion mechanism 13, a first storage tank 14, and a cascaded heat exchanger 30.

[0053] The first compressor 11 is a device for compressing a first refrigerant, such as a scroll compressor or other positive displacement compressor whose operating capacity can be varied by inverter control of the compressor motor.

[0054] The first heat exchanger 12 is a device for exchanging heat between a first refrigerant and outdoor air. In the first heat exchanger 12, the first refrigerant obtains either cold or heat energy from the outdoor air. The first heat exchanger 12 is, for example, a... Figure 3 The flat porous tube shown.

[0055] The first expansion mechanism 13 is a device for reducing the pressure of the first refrigerant, such as an electric expansion valve. The first expansion mechanism 13 is disposed between the first heat exchanger 12 and the cascaded heat exchanger 30.

[0056] The first storage tank 14 is located midway in the suction flow path connecting the cascaded heat exchanger 30 to the suction side of the first compressor 11. The first storage tank 14 separates the incoming refrigerant into liquid refrigerant and gaseous refrigerant, and allows only the gaseous refrigerant to flow to the suction side of the first compressor 11.

[0057] In this embodiment, the first storage tank 14 omits the conventional storage tank and is an auxiliary storage tank attached to the conventional storage tank. Specifically, the volume of the first storage tank 14 is less than half the volume of the second storage tank 26 of the second circuit 20, which will be described later.

[0058] The cascaded heat exchanger 30 is a device for exchanging heat between the first and second refrigerants without mixing them. The cascaded heat exchanger 30 is, for example, a plate heat exchanger. The cascaded heat exchanger 30 has a first flow path 31 belonging to the first loop 10 and a second flow path 32 belonging to the second loop 20. The gas side of the first flow path 31 is connected to the first compressor 11, and the liquid side is connected to the first expansion mechanism 13.

[0059] When the first heat exchanger 12 is used as a radiator and the second heat exchanger 23 of the second circuit 20 (described later) is used as a radiator, the cascaded heat exchanger 30 serves as an auxiliary to the second circuit 20 for the purpose of subcooling the second refrigerant that has been cooled in the second heat exchanger 23.

[0060] (2-2) Second circuit

[0061] The second refrigerant flowing in the second circuit 20 is not particularly limited; it may be the same as or different from the first refrigerant. Here, the second refrigerant is non-flammable, non-toxic, or has a GWP of 500 or less. For example, the second refrigerant is a spontaneously generated refrigerant; in this embodiment, the second refrigerant is carbon dioxide.

[0062] The second circuit 20 is configured as a main circuit for heating or cooling indoor air using a second refrigerant.

[0063] The second circuit 20 includes a second compressor 21, a switching mechanism 22, a second heat exchanger 23, a cascaded heat exchanger 30, a second expansion mechanism 24, a third heat exchanger 25, and a second storage tank 26.

[0064] The second compressor 21 is a device for compressing a second refrigerant, such as a scroll compressor or other positive displacement compressor whose operating capacity can be varied by inverter control of the compressor motor.

[0065] The switching mechanism 22 is a device for switching between a first state and a second state. In the first state, the second heat exchanger 23 functions as a radiator for the second refrigerant, and the third heat exchanger 25 functions as an evaporator for the second refrigerant (see reference). Figure 1 (Solid line of switching mechanism 22) In the second state, the second heat exchanger 23 functions as an evaporator for the second refrigerant, and the third heat exchanger 25 functions as a radiator for the second refrigerant (see reference). Figure 1 (The switching mechanism 22 is shown by the dashed line). The switching mechanism 22 is, for example, a four-way reversing valve. Furthermore, in its first state, the switching mechanism 22 connects the discharge side of the second compressor 21 to the gas side of the second heat exchanger 23, and connects the suction side of the second compressor 21 to the gas side of the third heat exchanger 25. In its second state, the switching mechanism 22 connects the discharge side of the second compressor 21 to the gas side of the third heat exchanger 25, and connects the suction side of the second compressor 21 to the gas side of the second heat exchanger 23.

[0066] The second heat exchanger 23 is a device for exchanging heat between the second refrigerant and outdoor air. In the second heat exchanger 23, the second refrigerant obtains cold or heat energy from the outdoor air. The second heat exchanger 23 is, for example, a cross-finned tube heat exchanger.

[0067] The second loop 20 has a second flow path 32 of a cascaded heat exchanger 30. In the second state, the gas side of the second flow path 32 is connected to the second heat exchanger 23, and the liquid side is connected to the third heat exchanger 25.

[0068] The second expansion valve 24 is a device for reducing the pressure of the second refrigerant, such as an electric expansion valve.

[0069] The third heat exchanger 25 is a device for heat exchange between the second refrigerant and outdoor air, and is, for example, a finned tube heat exchanger.

[0070] The second storage tank 26 is located in the middle of the suction flow path that connects the switching mechanism 22 to the suction side of the second compressor 21. The second storage tank 26 separates the incoming refrigerant into liquid refrigerant and gaseous refrigerant, and only allows the gaseous refrigerant to flow to the suction side of the second compressor 21.

[0071] (2-3) Outdoor Unit

[0072] In the following description, terms such as "up," "down," and "forward" are used appropriately to indicate the directions of the outdoor unit 2 when it is installed outdoors and is in normal use. In this embodiment, the up-down direction is the vertical direction.

[0073] Outdoor unit 2 is located in a space different from the space where indoor unit 3 is located. Here, outdoor unit 2 is located outdoors (near the roof of the building or the exterior wall of the building, etc.).

[0074] Outdoor unit 2 includes the aforementioned first circuit 10, a portion of the second circuit 20, housing 41, electrical mounting unit 42, fan 43, partition plate 44, separation plate 45, and various sensors. Specifically, outdoor unit 2 has... Figure 1 The components shown are: first compressor 11, first heat exchanger 12, first expansion mechanism 13, second compressor 21, switching mechanism 22, second heat exchanger 23, second expansion mechanism 24, second storage tank 26, cascaded heat exchanger 30, inlet temperature sensor 46, outlet temperature sensor 47, and... Figure 2 The shown components are: housing 41, electrical mounting unit 42, fan 43, partition plate 44, and separation plate 45.

[0075] The housing 41 houses the first compressor 11, the first heat exchanger 12, the first expansion mechanism 13, the second compressor 21, the switching mechanism 22, the second heat exchanger 23, the second expansion mechanism 24, the second storage tank 26, the cascaded heat exchanger 30, the electrical installation unit 42, the fan 43, the partition plate 44, the separation plate 45, and various sensors.

[0076] Figure 2 The housing 41 shown has a generally rectangular parallelepiped shape. Specifically, the housing 41 includes a front plate 411, a top plate 412, a bottom plate 413, and a side plate 414.

[0077] The front panel 411 is a plate-shaped component that forms the front side of the housing 41. The front panel 411 has an air outlet. The air outlet is an opening for blowing outdoor air that has been introduced into the housing 41 from the outside to the outside of the housing 41.

[0078] The top plate 412 is a plate-shaped component that forms the upper surface of the housing 41. The bottom plate 413 is a plate-shaped component that forms the lower surface of the housing 41. The top plate 412 and the bottom plate 413 are opposite to each other.

[0079] Side plate 414 is a plate-shaped component that forms the side of the housing 41. The lower part of side plate 414 is fixed to bottom plate 413.

[0080] The electrical mounting unit 42 is obtained by mounting electrical mounting components on a substrate. The electrical mounting components control the first compressor 11, the second compressor 21, the first expansion mechanism 13, the switching mechanism 22, the second expansion mechanism 24, and other controlled objects.

[0081] Fan 43 directs airflow to both the first heat exchanger 12 and the second heat exchanger 23. In this embodiment, fan 43 directs outdoor air to both the first heat exchanger 12 and the second heat exchanger 23. Here, fan 43 generates an airflow that guides outdoor air to the first heat exchanger 12 and the second heat exchanger 23, where it exchanges heat with the first refrigerant in the first heat exchanger 12 and with the second refrigerant in the second heat exchanger 23, before being discharged outdoors. Figure 2 Viewed from the front surface, fan 43 overlaps with the first heat exchanger 12 and the second heat exchanger 23. Fan 43 is driven by a fan motor.

[0082] Alternatively, separate fans can be installed to direct airflow to the first heat exchanger 12 and to direct airflow to the second heat exchanger 23.

[0083] The partition plate 44 is a plate-shaped component that extends in the vertical direction. The lower part of the partition plate 44 is fixed to the bottom plate 413 of the housing 41.

[0084] The partition plate 44 divides the interior of the shell 41 into a first chamber S1 and a second chamber S2. The first chamber S1 and the second chamber S2 are spaces formed by the front plate 411, top plate 412, bottom plate 413 and side plate 414 of the shell 41 and the partition plate 44, respectively.

[0085] Here, the first chamber S1 is an air supply chamber, which is a guide path for air drawn in from the intake of the outdoor unit 2 to flow to the outlet. In this embodiment, the first chamber S1 is equipped with a first heat exchanger 12, a second heat exchanger 23, a fan 43, etc.

[0086] The second compartment S2 is the machinery compartment. The second compartment S2 is equipped with a first compressor 11, a second compressor 21, a switching mechanism 22, a first expansion mechanism 13, a second expansion mechanism 24, a second storage tank 26, a cascaded heat exchanger 30, an electrical installation unit 42, etc.

[0087] The separation plate 45 divides the second chamber S2 into a first mechanical chamber S21 constituting the first circuit 10 and a second mechanical chamber S22 constituting the second circuit 20. The separation plate 45 is a plate-shaped component extending vertically. The lower part of the separation plate 45 is fixed to the bottom plate 413 of the housing 41. Here, the first mechanical chamber S21, which is divided by the front plate 411, top plate 412, bottom plate 413, side plate 414, and separation plate 45, is equipped with a first compressor 11, a first expansion mechanism 13, a cascaded heat exchanger 30, etc. The second mechanical chamber S22, which is divided by the front plate 411, top plate 412, bottom plate 413, partition plate 44, and separation plate 45, is equipped with a second compressor 21, a switching mechanism 22, a second expansion mechanism 24, a second storage tank 26, an electrical installation unit 42, etc.

[0088] The inlet temperature sensor 46 detects the temperature of the second refrigerant flowing into the cascade heat exchanger 30 during refrigeration operation. The outlet temperature sensor 47 detects the temperature of the second refrigerant after passing through the cascade heat exchanger 30 during refrigeration operation.

[0089] (2-4) Indoor Units

[0090] Indoor unit 3 is located indoors (inside the building). As described above, indoor unit 3 is connected to outdoor unit 2 via connecting pipes 4 and 5 and forms part of the second circuit 20.

[0091] like Figure 1 As shown, the indoor unit 3 has a third heat exchanger 25. Here, the indoor unit 3 is installed by means of embedding or hanging in the indoor ceiling of a building or the like, or by wall mounting on the indoor wall.

[0092] (2-5) Connecting pipes

[0093] Connecting pipes 4 and 5 are refrigerant pipes installed on-site when the refrigeration cycle unit 1 is installed in a building or other similar location. One end of the liquid-side connecting pipe 4 is connected to the liquid-side end of the outdoor unit 2, and the other end of the connecting pipe 4 is connected to the liquid-side end of the third heat exchanger 25 of the indoor unit 3. One end of the gas-side connecting pipe 5 is connected to the gas-side end of the outdoor unit 2, and the other end of the connecting pipe 5 is connected to the gas-side end of the third heat exchanger 25 of the indoor unit 3.

[0094] (2-6) Control Department

[0095] (2-6-1) Summary

[0096] The aforementioned outdoor unit 2 and indoor unit 3 are controlled by the control unit 6. The control unit 6 is configured to communicate with the electrical installation unit 42 and the control board (not shown) provided in the indoor unit 3 via an electrical installation unit 42 and the like provided in the outdoor unit 2.

[0097] like Figure 4 As shown, the control unit 6 controls the components of the refrigeration cycle unit 1 (here, the outdoor unit 2 and the indoor unit 3). In other words, the control unit 6 controls the operation of the entire refrigeration cycle unit 1. Therefore, in this embodiment, the control unit 6 controls the operation of the first loop 10 and the second loop 20. Here, the control unit 6 is provided in the unit constituting the second loop 20 ( Figure 2 The second mechanical room (S22) starts operating based on the operation of the second circuit 20, which in turn starts operating the first circuit 10.

[0098] The control unit 6 is implemented via a computer. The controller 6 includes a control processing unit and a storage unit. A processor such as a CPU or GPU can be used in the control processing unit. The control processing unit reads the program stored in the storage unit and performs prescribed image processing or computational processing according to the program. Furthermore, the control processing unit can write the computation results to the storage unit according to the program, and can also read information stored in the storage unit according to the program.

[0099] (2-6-2) Stop control

[0100] The control unit 6 performs stop control, in which the first refrigerant is concentrated in the first heat exchanger 12 before the operation of the first circuit 10 is stopped. The stop control is as follows: when the control unit 6 receives a command to stop the first compressor 11, it operates the first compressor 11 to pressurize the first refrigerant of the first circuit 10 into the first heat exchanger 12, and then stops the first compressor 11. Therefore, even if the control unit 6 receives a command to stop the first compressor 11, it does not immediately stop the first compressor 11, but rather continues the operation of the first compressor 11 for a short time to pressurize the first refrigerant into the first heat exchanger 12 before stopping the first compressor 11.

[0101] In addition, the time when the first compressor 11 is stopped in the stop control is, for example, when a predetermined time has elapsed since the command to stop the operation of the first circuit 10, and the pressure or pressure equivalent temperature on the high-pressure side is above a predetermined value or the pressure or pressure equivalent temperature on the low-pressure side is below a predetermined value.

[0102] Furthermore, in this embodiment, when the second circuit 20 is in heating operation and the first circuit 10 is in a stopped state, the control unit 6 sets the first expansion mechanism 13 to be fully closed.

[0103] (2-6-3) Start control

[0104] During refrigeration operation, the control unit 6 performs start control, in which the second circuit 20 is operated before the first circuit 10 is operated. During start control, when the control unit 6 receives a command to start the first circuit 10, it starts the second compressor 21 before starting the first compressor 11.

[0105] Specifically, the control unit 6 starts operation of the first circuit 10 when the difference between the inlet and outlet temperatures of the cascaded heat exchanger 30 in the second circuit 20 falls below a predetermined value. Here, the control unit 6 obtains the temperature of the second refrigerant flowing into the cascaded heat exchanger 30 from the inlet temperature sensor 46 and the temperature of the second refrigerant flowing out of the cascaded heat exchanger 30 from the outlet temperature sensor 47. Furthermore, the control unit 6 calculates the temperature difference between the inlet and outlet temperatures of the second refrigerant in the cascaded heat exchanger 30 to determine whether the temperature difference is below a predetermined value. For example, the temperature difference is 5°C or less, and preferably 2°C or less. When the control unit 6 determines that the calculated temperature difference is below the predetermined value, the control unit 6 starts the first compressor 11. On the other hand, when the control unit 6 determines that the calculated temperature difference is not below the predetermined value, the control unit 6 does not start the first compressor 11.

[0106] After the first compressor 11 starts, the control unit 6 increases the opening of the first expansion mechanism 13. Here, to prevent the first refrigerant accumulated in the first flow path 31 of the cascaded heat exchanger 30 from immediately flowing and liquefying into the first compressor 11, the control unit 6 keeps the first expansion mechanism 13 at a slightly open opening, smaller than during refrigeration operation. After the first refrigerant begins to circulate, the control unit 6 controls the opening of the first expansion mechanism 13 according to the load.

[0107] In this embodiment, the control unit 6 starts the second compressor 21, then increases the opening of the second expansion mechanism 24, then starts the first compressor 11, and then increases the opening of the first expansion mechanism 13. At this time, the opening of the first expansion mechanism 13 is smaller than the opening of the second expansion mechanism 24.

[0108] (3) Actions

[0109] Reference Figures 1 to 8 The operation of the refrigeration circulation unit 1 will be explained. The refrigeration circulation unit 1 is capable of both heating operation (heating the indoor air) and cooling operation (cooling the indoor air) for indoor air conditioning. During both heating and cooling operations, the operation of the refrigeration circulation unit 1 is controlled by the control unit 6.

[0110] (3-1) Heating Operation

[0111] like Figure 5As shown, during heating operation, the switching mechanism 22 is switched to the second state (the state indicated by the dashed line), so that the second heat exchanger 23 functions as an evaporator for the second refrigerant, and the third heat exchanger 25 functions as a radiator for the second refrigerant. Furthermore, during heating operation, the first compressor 11 is not started, thus preventing the first refrigerant in the first circuit 10 from circulating. Here, the first expansion mechanism 13 is set to be fully closed.

[0112] In the second circuit 20, the second refrigerant discharged from the second compressor 21 flows out from the outdoor unit 2 through the switching mechanism 22.

[0113] Refrigerant flowing from outdoor unit 2 flows into indoor unit 3 via gas-side connecting pipe 5. In indoor unit 3, a second refrigerant is supplied to a third heat exchanger 25. The second refrigerant supplied to the third heat exchanger 25 is cooled by exchanging heat with indoor air, thereby dissipating heat. The second refrigerant, after dissipating heat in the third heat exchanger 25, flows out of indoor unit 3.

[0114] The second refrigerant flowing from indoor unit 3 flows into outdoor unit 2 via liquid-side connecting pipe 4. In outdoor unit 2, the second refrigerant is conveyed to second heat exchanger 23 via second expansion mechanism 24 and second flow path 32 of cascaded heat exchanger 30. The second refrigerant conveyed to second heat exchanger 23 is heated by heat exchange with outdoor air supplied by fan 43, thereby evaporating. The second refrigerant evaporated in second heat exchanger 23 passes through switching mechanism 22 and second storage tank 26 and is drawn back into second compressor 21.

[0115] (3-2) Refrigeration operation

[0116] like Figure 6 As shown, during refrigeration operation, the switching mechanism 22 is switched to the first state (the state of the switching mechanism 22 is the solid line) so that the second heat exchanger 23 functions as a radiator for the second refrigerant and the third heat exchanger 25 functions as an evaporator for the second refrigerant.

[0117] In the second circuit 20, the second refrigerant discharged from the second compressor 21 is conveyed to the second heat exchanger 23 via the switching mechanism 22. The second refrigerant conveyed to the second heat exchanger 23 is cooled by exchanging heat with the outdoor air supplied by the fan 43, thereby dissipating heat. The second refrigerant, after being cooled in the second heat exchanger 23, is conveyed to the second flow path 32 of the cascaded heat exchanger 30. The second refrigerant conveyed to the second flow path 32 is further cooled by exchanging heat with the first refrigerant flowing in the first flow path 31 in the cascaded heat exchanger 30. The second refrigerant, after being further cooled in the cascaded heat exchanger 30, is depressurized by the second expansion mechanism 24 and then flows out from the outdoor unit 2.

[0118] The second refrigerant flowing from the outdoor unit 2 flows into the indoor unit 3 via the liquid-side connecting pipe 4. In the indoor unit 3, the second refrigerant is supplied to the third heat exchanger 25. The second refrigerant supplied to the third heat exchanger 25 is heated by exchanging heat with the indoor air, thereby evaporating. The second refrigerant, after evaporating in the third heat exchanger 25, flows out of the indoor unit 3.

[0119] The second refrigerant flowing from the indoor unit 3 flows into the outdoor unit 2 via the gas-side connecting pipe 5. In the outdoor unit 2, the second refrigerant passes through the switching mechanism 22 and the second storage tank 26 and is drawn back into the second compressor 21.

[0120] In the first circuit 10, the first refrigerant discharged from the first compressor 11 is conveyed to the first heat exchanger 12. The first refrigerant conveyed to the first heat exchanger 12 is cooled by exchanging heat with outdoor air supplied by the fan 43, thereby dissipating heat. After dissipating heat in the first heat exchanger 12, the first refrigerant is depressurized by the first expansion mechanism 13 and then conveyed to the first flow path 31 of the cascaded heat exchanger 30. The first refrigerant conveyed to the first flow path 31 is heated by exchanging heat with the second refrigerant flowing in the second flow path 32 in the cascaded heat exchanger 30, thereby evaporating. The first refrigerant, after evaporation in the cascaded heat exchanger 30, passes through the first storage tank 14 and is drawn back into the first compressor 11.

[0121] (3-3) The operation of the first circuit stops.

[0122] When a command to stop the cooling operation is received from a remote control or the like, the control unit 6 stops the operation of the first circuit 10 and the second circuit 20.

[0123] Specifically, the control unit 6, upon receiving the instruction, stops the second compressor 21, but as Figure 7 As shown, the operation of the first compressor 11 continues (step S101). This allows the first refrigerant to be concentrated in the first heat exchanger 12.

[0124] Furthermore, the opening degree of the first expansion mechanism 13 is reduced by the control unit 6 (step S102). Here, the first expansion mechanism 13 is set to be fully closed.

[0125] Furthermore, when the control unit 6 determines that the first refrigerant has been concentrated in the first heat exchanger 12, it stops the first compressor 11 (step S103). As a result, the operation of the first circuit 10 can be stopped.

[0126] Alternatively, after the first compressor 11 stops, the opening degree of the first expansion mechanism 13, which is in a fully closed state, can be set to slightly open.

[0127] (3-4) The operation of the first circuit begins.

[0128] When a command to start cooling operation is received from a remote control or the like, the control unit 6 starts the operation of the second circuit 20 before the first circuit 10 starts operating.

[0129] Specifically, such as Figure 8 As shown, the second compressor 21 is started by the control unit 6 upon receiving the instruction (step S111). Next, the opening of the second expansion mechanism 24 is increased (step S112). Through steps S111 and S112, the second refrigerant circulates in the second circuit 20, thereby heating the liquefied first refrigerant in the cascaded heat exchanger 30.

[0130] Next, the control unit 6 determines whether the difference between the inlet temperature and the outlet temperature of the cascaded heat exchanger 30 in the second loop 20 has fallen below a predetermined value (step S113). In this step S113, the determination is made by the temperature difference between the inlet temperature detected by the inlet temperature sensor 46 and the outlet temperature detected by the outlet temperature sensor 47.

[0131] When it is determined in step S113 that the temperature difference is not below the specified value, it is determined that the first refrigerant of the cascade heat exchanger 30 has liquefied, and the operation of the first circuit 10 is not started, but the operation of the second circuit 20 continues.

[0132] On the other hand, when it is determined in step S113 that the temperature difference is below a predetermined value, it is determined that the first refrigerant in the cascade heat exchanger 30 has vaporized, and the operation of the first circuit 10 begins. As the start of the operation of the first circuit 10, the first compressor 11 is first started by the control unit 6 (step S114). Then, the opening of the first expansion mechanism 13 is increased (step S115).

[0133] (4) Characteristics

[0134] (4-1)

[0135] The refrigeration cycle device 1 of this embodiment includes a first circuit 10, a second circuit 20, and a control unit 6. The first circuit 10 includes a first compressor 11, a first heat exchanger 12, a first expansion mechanism 13, and a cascaded heat exchanger 30. The first circuit 10 supplies a first refrigerant. The second circuit 20 includes a second compressor 21, a second heat exchanger 23, a cascaded heat exchanger 30, a second expansion mechanism 24, and a third heat exchanger 25. The second circuit 20 supplies a second refrigerant. The control unit 6 performs stop control, in which the first refrigerant is concentrated in the first heat exchanger 12 before stopping the operation of the first circuit 10.

[0136] In the refrigeration cycle apparatus 1 of this embodiment, the control unit 6 performs stop control to concentrate the first refrigerant into the first heat exchanger 12 before stopping the operation of the first circuit 10. Therefore, the amount of first refrigerant concentrated into the cascade heat exchanger 30 can be reduced. Thus, by cooling the first refrigerant in the cascade heat exchanger 30 during the shutdown of the first circuit 10, liquefaction can be suppressed. Operating the first circuit 10 in this state further prevents the liquefied first refrigerant from flowing into the first compressor 11. Therefore, the compression (liquid compression) of the liquefied first refrigerant by the first compressor 11 can be suppressed, thereby reducing the likelihood of malfunctions in the first compressor 11.

[0137] (4-2)

[0138] The refrigeration cycle device 1 of this embodiment is based on the refrigeration cycle device 1 of (4-1) above. When the refrigeration is running, the control unit 6 operates the second circuit 20 before the first circuit 10 is operated.

[0139] Here, by operating the second circuit 20 before the first circuit 10, the high-pressure second refrigerant, after passing through the second heat exchanger 23 of the second circuit 20, can transfer heat to the first refrigerant concentrated in the cascade heat exchanger 30 as it passes through the cascade heat exchanger 30. This heat can heat the first refrigerant, thus causing the liquefied first refrigerant to vaporize. Therefore, it is possible to further suppress the flow of the liquefied first refrigerant into the first compressor 11.

[0140] In particular, the control unit 6 preferably operates the second circuit 20 before the first circuit 10 operates during the initial cooling operation after the heating operation. The reason for this will be explained.

[0141] If, during heating operation, the second circuit 20 is operated instead of the first circuit 10, the cooled second refrigerant flows to the second flow path 32 of the second circuit 20 belonging to the cascaded heat exchanger 30. Therefore, if the first refrigerant is stored in the first flow path 31 of the first circuit 10 belonging to the cascaded heat exchanger 30, the first refrigerant will be cooled and liquefied. In this state, during the initial cooling operation after heating operation, when the first circuit 10 starts operating, the liquefied first refrigerant in the first flow path 31 of the cascaded heat exchanger 30 flows into the first compressor 11. However, during the initial cooling operation after heating operation, if the second circuit 20 is operated before the first circuit 10, the high-pressure second refrigerant after passing through the second heat exchanger 23 can vaporize the liquefied first refrigerant in the first flow path 31 of the cascaded heat exchanger 30 when it passes through the second flow path 32 of the cascaded heat exchanger 30.

[0142] (4-3)

[0143] The refrigeration cycle device 1 of this embodiment is based on the refrigeration cycle device 1 of (4-2) above. When the difference between the inlet temperature and the outlet temperature of the cascaded heat exchanger 30 in the second loop 20 becomes below a predetermined value, the operation of the first loop 10 is started.

[0144] Here, when the difference between the inlet and outlet temperatures of the cascaded heat exchanger 30 in the second circuit 20 falls below a predetermined value, it is determined that heat from the second refrigerant has been transferred to the first refrigerant in the cascaded heat exchanger 30, causing the first refrigerant to vaporize. Under these conditions, the first circuit 10 is operated, thus further preventing the liquefied first refrigerant from flowing into the first compressor 11.

[0145] (4-4)

[0146] The refrigeration cycle device of this embodiment is based on any of the refrigeration cycle devices in (4-1) to (4-3) above, except that after the first compressor 11 is started, the opening degree of the first expansion mechanism 13 is increased.

[0147] Here, when the first compressor 11 starts, the opening degree of the first expansion mechanism 13 is slightly open or fully closed, thus preventing the first refrigerant in the first circuit 10 from directly flowing into the first compressor 11. Therefore, it is possible to further prevent the liquefied first refrigerant from flowing into the first compressor 11.

[0148] (4-5)

[0149] The refrigeration cycle device 1 of this embodiment is based on the refrigeration cycle device 1 of (4-4) above. The control unit 6 starts the second compressor 21, then increases the opening of the second expansion mechanism 24, then starts the first compressor 11, and then increases the opening of the first expansion mechanism 13.

[0150] Thus, by controlling the first circuit 10 and the second circuit 20 in the order of the second compressor 21, the second expansion mechanism 24, the first compressor 11 and the first expansion mechanism 13, the first circuit 10 and the second circuit 20 can be operated while suppressing the flow of the liquefied first refrigerant into the first compressor 11.

[0151] (4-6)

[0152] The refrigeration cycle device 1 of this embodiment is based on any of the refrigeration cycle devices 1 in (4-1) to (4-5) above, and the control unit 6 controls the operation of the first circuit 10 and the operation of the second circuit 20.

[0153] Thus, in the refrigeration cycle apparatus 1 disclosed herein, the control unit of the second loop 20 can also control the first loop 10.

[0154] (4-7)

[0155] Based on any of the above-described (4-1) to (4-6) refrigeration cycle devices 1, the first heat exchanger 12 of this embodiment is a flat porous tube.

[0156] Here, the flat, porous tube serving as the first heat exchanger 12 can reduce its volume, thus reducing the amount of the first refrigerant. Therefore, the amount of the first refrigerant concentrated in the cascaded heat exchanger 30 can be reduced.

[0157] (4-8)

[0158] The refrigeration circulation device 1 of this embodiment is based on any of the refrigeration circulation devices 1 in (4-1) to (4-7) above, and further includes a fan 43 for supplying outdoor air to the first heat exchanger 12 and the second heat exchanger 23.

[0159] Here, the fan 43 supplying outdoor air to both the first heat exchanger 12 and the second heat exchanger 23 is shared. Therefore, even if the first circuit 10 is stopped, outdoor air will still flow to the first heat exchanger 12 while the second circuit 20 is operating. Consequently, the first refrigerant concentrated in the first heat exchanger 12 exchanges heat with the outdoor air, thus easily concentrating the liquefied first refrigerant in the first heat exchanger 12. This further suppresses the flow of the liquefied first refrigerant into the first compressor 11.

[0160] (4-9)

[0161] The refrigeration cycle device 1 of this embodiment is based on any of the refrigeration cycle devices 1 in (4-1) to (4-8) above, and the first loop 10 further includes a first storage tank 14.

[0162] Here, the liquefied first refrigerant can be stored in the first storage tank 14, thus further preventing the liquefied first refrigerant from flowing into the first compressor 11.

[0163] Furthermore, even if a first storage tank 14 is provided in the first circuit 10, it is not possible to completely prevent liquid refrigerant from flowing into the first compressor 11. Therefore, by performing the stop control of this embodiment, the liquid compression is suppressed.

[0164] (4-10)

[0165] The refrigeration cycle device 1 of this embodiment is based on any of the refrigeration cycle devices 1 in (4-1) to (4-9) above. When the second circuit 20 is in heating operation and the first circuit 10 is in a stop operation, the control unit 6 sets the first expansion mechanism 13 to be fully closed.

[0166] When the second circuit 20 is in heating operation, the low-pressure second refrigerant passes through the second flow path 32 of the cascaded heat exchanger 30. Therefore, when the second circuit 20 is in heating operation and the first circuit 10 is stopped, the first refrigerant concentrated in the first flow path 31 of the cascaded heat exchanger 30 is cooled, making it easier to liquefy. In this case, by setting the first expansion mechanism 13 to be fully closed, the amount of first refrigerant flowing into the cascaded heat exchanger 30 and liquefying can be reduced. Therefore, it is possible to further suppress the flow of liquefied first refrigerant into the first compressor 11.

[0167] (4-11)

[0168] The refrigeration cycle device 1 of this embodiment is based on any of the refrigeration cycle devices 1 in (4-1) to (4-10) described above, and the control unit 6 performs heating operation and cooling operation.

[0169] Here, when the first circuit 10 is stopped during heating operation, the first refrigerant concentrated in the cascaded heat exchanger 30 is prone to liquefaction, thus potentially causing the liquefied first refrigerant to flow into the first compressor 11. Even in the event that this problem is likely to occur, the flow of liquefied first refrigerant into the first compressor 11 can be prevented by performing a stop control.

[0170] (4-12)

[0171] The refrigeration cycle device 1 of this embodiment is based on any of the refrigeration cycle devices 1 in (4-1) to (4-11) above, wherein the first refrigerant is flammable, toxic, or has a GWP of more than 500.

[0172] Thus, a first refrigerant that is flammable, toxic, or has a GWP exceeding 500 can be used.

[0173] (4-12)

[0174] The refrigeration cycle device 1 of this embodiment is based on the refrigeration cycle device 1 of (4-12) above, wherein the first refrigerant is R290 and the second refrigerant is carbon dioxide.

[0175] Carbon dioxide refrigerant has a low GWP, thus it can help suppress global warming, but it is difficult to perform well in refrigeration operation when the outside air temperature is high. In this regard, the refrigeration cycle device 1 of this embodiment includes a first loop 10 for R290 circulation as a subcooling loop, thus improving the capacity.

[0176] (5) Variations

[0177] (5-1) Variation Example 1

[0178] (5-1-1) Start Control

[0179] In the above embodiment, as an example of starting control during refrigeration operation, the operation of the first circuit 10 is described when the difference between the inlet temperature and the outlet temperature of the cascaded heat exchanger 30 in the second circuit 20 becomes below a predetermined value. However, this is not a limitation. In this modified example, the control unit 6 starts the operation of the first circuit 10 after a predetermined time has elapsed since the start of operation of the second circuit 20. The predetermined time is, for example, 3 minutes or more, and preferably 10 minutes or more.

[0180] Here, as Figure 9 As shown, the control unit 6 determines whether a predetermined time has elapsed since the second compressor 21 was started (step S116). When the control unit 6 determines that the predetermined time has elapsed, the control unit 6 starts the first compressor 11 (step S114). On the other hand, when the control unit 6 determines that the predetermined time has not elapsed, the control unit 6 does not start the first compressor 11.

[0181] (5-1-2) Features

[0182] The refrigeration cycle device in this modified example is based on the refrigeration cycle device described above (4-2). After a predetermined time has elapsed since the start of operation of the second circuit 20, the control unit 6 starts operation of the first circuit 10.

[0183] Here, when a predetermined time has elapsed since the start of operation of the second circuit 20, it is determined that heat from the second refrigerant has been transferred to the first refrigerant in the cascaded heat exchanger 30, causing the first refrigerant to vaporize. Under these conditions, operation of the first circuit 10 is performed, thus further preventing the liquefied first refrigerant from flowing into the first compressor 11.

[0184] (5-2) Variation Example 2

[0185] In the above embodiment, the control unit 6 is described as setting the first expansion mechanism 13 to be fully closed when the second circuit 20 is in heating operation and the first circuit 10 is stopped, but it is not limited to this. Even when the second circuit 20 is in cooling operation and the first circuit 10 is stopped, the first expansion mechanism 13 can still be set to be fully closed.

[0186] Thus, in this modified example, when the second circuit 20 is in operation and the first circuit 10 is in a stop, the control unit 6 sets the first expansion mechanism 13 to be fully closed.

[0187] When the second circuit 20 is operating and the first circuit 10 is stopped, the first refrigerant is easily cooled in the cascade heat exchanger 30. In this case, in the refrigeration cycle apparatus of this modified example, by setting the first expansion mechanism 13 to be fully closed, the flow of the first refrigerant into the cascade heat exchanger 30 can be reduced. Therefore, it is possible to further suppress the flow of the liquefied first refrigerant into the first compressor 11.

[0188] (5-3) Variation Example 3

[0189] In the above embodiment, the start control and stop control are described as examples of starting and stopping the refrigeration operation. However, the start control and stop control can also be applied to stop or start the operation of the first circuit 10 during the refrigeration operation.

[0190] Specifically, the control unit 6 can also control the operation of the first circuit 10 according to the load during cooling operation. More specifically, the control unit 6 does not operate the first circuit 10 when the load during cooling operation is low, but operates the first circuit 10 when the load during cooling operation is high. In this case, when the load increases during cooling operation, the control unit 6 performs the aforementioned start control when operating the first circuit 10. Furthermore, when the load decreases during cooling operation, the control unit 6 performs the aforementioned stop control when stopping the operation of the first circuit 10.

[0191] (5-4) Variation Example 4

[0192] In the above embodiment, the case in which the control unit 6 is provided in the second mechanical room S22 of the second circuit 20 and the operation of the first circuit 10 is started based on the start of the operation of the second circuit 20 is described as an example, but it is not limited to this.

[0193] In this modified example, the control unit includes a first control unit that controls the operation of the first circuit 10 and a second control unit that controls the operation of the second circuit 20. The first control unit starts the operation of the first circuit 10 based on the instructions from the second control unit.

[0194] (5-5) Variation Example 5

[0195] In the above embodiments, the first circuit 10 has a first storage tank 14, but is not limited thereto. The first circuit of this disclosure may also have a storage tank and an auxiliary storage tank.

[0196] In this variation, the first circuit does not have either a storage tank or an auxiliary storage tank. Therefore, the amount of first refrigerant filled into the first circuit 10 can be further reduced. Thus, the refrigeration cycle unit 1 is very useful when using a highly flammable (A3) refrigerant such as R290.

[0197] (5-6) Variation Example Six

[0198] In the above embodiment, the example described is that a common fan 43 supplies outdoor air to the first heat exchanger 12 and the second heat exchanger 23, but it is not limited to this. The refrigeration cycle apparatus of this modified example has a first fan that supplies outdoor air to the first heat exchanger 12 and a second fan that supplies outdoor air to the second heat exchanger 23, and the first fan and the second fan are different.

[0199] (5-7) Variation Example 7

[0200] In the above embodiment, a refrigeration cycle device 1 with one indoor unit 3 connected to one outdoor unit 2 was described as an example, but it is not limited to this. In the refrigeration cycle device of this modified example, multiple indoor units are connected to one outdoor unit.

[0201] (5-8) Variation Example 8

[0202] In the above embodiments, a refrigeration cycle device 1 that performs both cooling and heating operations has been described as an example, but it is not limited to this. The refrigeration cycle device of this disclosure can also perform dehumidification operation. During dehumidification operation, stop control and start control are performed in the same manner as during cooling operation in the above embodiments. Furthermore, the refrigeration cycle device of this disclosure can also be an air conditioning device specifically for refrigeration.

[0203] The embodiments of this disclosure have been described above. However, it should be understood that various changes in form and detail can be made without departing from the spirit and scope of this disclosure as set forth in the claims.

[0204] Symbol Explanation

[0205] 1. Refrigeration circulation unit; 6. Control Department; 10. First circuit; 11. First compressor; 12. First heat exchanger; 13 First expansion mechanism; 14 First storage tank (storage tank); 20. Second circuit; 21. Second compressor; 23. Second heat exchanger; 24. Second expansion mechanism; 25. Third heat exchanger; 30-tier heat exchanger; 43. Fan.

[0206] Existing technical documents

[0207] Patent documents

[0208] Patent Document 1: Japanese Patent No. 5430604.

Claims

1. A refrigeration circulation device (1), characterized in that, include: The first circuit (10) includes a first compressor (11), a first heat exchanger (12), a first expansion mechanism (13), and a cascaded heat exchanger (30), and supplies a first refrigerant for circulation; The second circuit (20), comprising a second compressor (21), a second heat exchanger (23), the cascaded heat exchanger (30), a second expansion mechanism (24), and a third heat exchanger (25), provides a second refrigerant circulation; and The control unit (6) performs stop control to concentrate the first refrigerant into the first heat exchanger before stopping the operation of the first circuit.

2. The refrigeration cycle apparatus according to claim 1, characterized in that, When the cooling system is in operation, the control unit operates the second circuit before the first circuit operates.

3. The refrigeration cycle apparatus according to claim 2, characterized in that, When the difference between the inlet temperature and the outlet temperature of the cascaded heat exchanger in the second loop reaches a predetermined value or below, the control unit starts the operation of the first loop.

4. The refrigeration cycle apparatus according to claim 2, characterized in that, The control unit starts operating the first circuit after a predetermined time has elapsed since the second circuit began operating.

5. The refrigeration cycle apparatus according to any one of claims 1 to 4, characterized in that, The control unit increases the opening of the first expansion mechanism after the first compressor is started.

6. The refrigeration cycle apparatus according to claim 5, characterized in that, The control unit starts the second compressor, then increases the opening of the second expansion mechanism, then starts the first compressor, and then increases the opening of the first expansion mechanism.

7. The refrigeration cycle apparatus according to any one of claims 1 to 6, characterized in that, The control unit controls the operation of the first circuit and the second circuit.

8. The refrigeration cycle apparatus according to any one of claims 1 to 7, characterized in that, The first heat exchanger is a flat porous tube.

9. The refrigeration cycle apparatus according to any one of claims 1 to 8, characterized in that, The refrigeration cycle device also includes a fan (43) that delivers outdoor air to the first heat exchanger and the second heat exchanger.

10. The refrigeration cycle apparatus according to any one of claims 1 to 9, characterized in that, The first loop also includes a storage tank (14).

11. The refrigeration cycle apparatus according to any one of claims 1 to 10, characterized in that, When the second circuit is in operation and the first circuit is stopped, the control unit sets the first expansion mechanism to be fully closed.

12. The refrigeration cycle apparatus according to any one of claims 1 to 11, characterized in that, The control unit performs heating and cooling operations.

13. The refrigeration cycle apparatus according to any one of claims 1 to 12, characterized in that, The first refrigerant is flammable, toxic, or has a GWP exceeding 500.

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