Refrigeration apparatus

Abstract

A refrigeration apparatus (1) comprises: a first circuit (10) in which a first refrigerant circulates and which has a first heat exchanger (13); and a second circuit (20) in which a second refrigerant circulates and which has a second heat exchanger (22). In a cascade heat exchanger, heat is exchanged between the first refrigerant and the second refrigerant. The first heat exchanger (13) includes a first heat transfer tube (131) and an anti-freezing tube (132) disposed therebelow. The cascade heat exchanger includes a second heat transfer tube constituting a part of the first circuit (10), and a third heat transfer tube constituting a part of the second circuit (20). During heating operation, the first refrigerant can flow through the second heat transfer tube, the anti-freezing tube (132), and the first heat transfer tube (131) in this order. During cooling operation, the first refrigerant can flow from the first heat transfer tube (131) to the second heat transfer tube in this order without passing through the anti-freezing tube (132).

Description

Refrigeration equipment

[0001] Regarding refrigeration equipment.

[0002] The air conditioning apparatus of Patent Document 1 (JP 2007-232274 A) is equipped with a refrigerant circuit having a compressor, an outdoor heat exchanger, an outdoor unit electric expansion valve, an indoor heat exchanger, and an indoor unit electric expansion valve, and the outdoor heat exchanger has a subcooling pipe located at the lowest stage.

[0003] The present inventors have noticed the problem that performance deteriorates when the outdoor heat exchanger of Cited Document 1 is applied to a two-stage refrigeration system that includes a first refrigerant circuit that uses a first refrigerant, a second refrigerant circuit that assists heat dissipation from the first refrigerant circuit, and a cascade heat exchanger that exchanges heat between the first refrigerant and the second refrigerant.

[0004] The inventors discovered that this problem is caused by the fact that a cascade refrigeration system has a third heat exchanger disposed between the outdoor heat exchanger and the indoor heat exchanger, unlike the air conditioner of Patent Document 1. When such a cascade refrigeration system performs cooling operation, the refrigerant whose temperature has been excessively reduced by the subcooling pipe of the outdoor heat exchanger flows into the third heat exchanger, resulting in a decrease in energy consumption efficiency (COP: Coefficient of Performance).

[0005] Therefore, a refrigeration apparatus according to a first aspect includes a first circuit and a second circuit. A first refrigerant circulates in the first circuit and includes a first heat exchanger. A second refrigerant circulates in the second circuit and includes a second heat exchanger. The first refrigerant and the second refrigerant exchange heat in a cascade heat exchanger. The first heat exchanger includes a first heat transfer tube and a freeze prevention tube. The freeze prevention tube is disposed below the first heat transfer tube. The cascade heat exchanger includes a second heat transfer tube and a third heat transfer tube. The second heat transfer tube constitutes a part of the first circuit. The third heat transfer tube constitutes a part of the second circuit. During heating operation, the first refrigerant is configured to flow through the second heat transfer tube, the freeze prevention tube, and the first heat transfer tube in this order. During cooling operation, the first refrigerant is configured to flow from the first heat transfer tube to the second heat transfer tube without passing through the freeze prevention tube.

[0006] According to the first aspect of the present invention, in a two-stage refrigeration system including a first circuit and a second circuit, the first refrigerant can flow through the antifreeze pipe during heating operation. In this case, pressure loss occurs in the antifreeze pipe, causing the saturation temperature to rise above freezing, thereby suppressing ice growth caused by frozen water.

[0007] Furthermore, in a two-stage refrigeration system having a first circuit and a second circuit, the first refrigerant can bypass the freeze prevention pipe during cooling operation. This prevents the temperature of the first refrigerant from dropping excessively in the first heat exchanger. This first refrigerant flows into the cascade heat exchanger and exchanges heat with the second refrigerant, promoting heat exchange between the first refrigerant and the second refrigerant in the cascade heat exchanger. This prevents a decrease in the performance of the refrigeration system.

[0008] A refrigeration apparatus according to a second aspect is the refrigeration apparatus according to the first aspect, wherein the first heat exchanger further includes a pipe and a valve. The pipe is connected to the freeze prevention pipe. The valve is provided in the pipe. The valve is at least one of an on-off valve, a three-way valve, and a check valve.

[0009] In the refrigeration system of the second aspect, a configuration in which the first refrigerant bypasses the anti-freeze pipe and a configuration in which the first refrigerant flows through the anti-freeze pipe can be easily realized by using piping connected to the anti-freeze pipe and at least one valve selected from an on-off valve, a three-way valve, and a check valve provided on the piping.

[0010] A refrigeration apparatus according to a third aspect is the refrigeration apparatus according to the second aspect, wherein the piping includes a bypass pipe that branches off from a portion connected to the freeze prevention pipe, into which the first refrigerant flows during heating operation, toward the first heat transfer pipe.

[0011] In the refrigeration device of the third aspect, a configuration in which the first refrigerant bypasses the anti-freeze pipe can be more easily realized by passing the first refrigerant through the bypass pipe using at least one of an on-off valve, a three-way valve, and a check valve.

[0012] A refrigeration apparatus according to a fourth aspect is the refrigeration apparatus according to any one of the first aspect to the third aspect, wherein the operation of the second circuit is stopped during heating operation.

[0013] As in the refrigeration apparatus of the fourth aspect, if the performance is not improved by operating the second circuit during heating operation, it is possible to not use the second circuit, in which case the decrease in efficiency during heating operation can be suppressed.

[0014] A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to any one of the first to fourth aspects, wherein the second heat exchanger is disposed downwind of the first heat exchanger. The first and second heat exchangers are disposed in a first direction. The second heat exchanger overlaps with the freeze prevention pipe when viewed in the first direction.

[0015] In the refrigeration system of the fifth aspect, the first refrigerant does not flow through the freeze prevention pipe, or the first refrigerant flowing through the freeze prevention pipe is at a lower temperature than the first refrigerant flowing through the first heat transfer pipe. Therefore, the air that has passed through the freeze prevention pipe is at a relatively low temperature. In the refrigeration system of the fifth aspect, the second heat exchanger is disposed on the downwind side of the freeze prevention pipe, so that a decrease in the heat exchange efficiency between the air that has passed through the first heat exchanger and the second refrigerant in the second heat exchanger can be suppressed.

[0016] A refrigeration apparatus according to a sixth aspect is the refrigeration apparatus according to any one of the first aspect to the fifth aspect, wherein the first refrigerant includes carbon dioxide refrigerant.

[0017] In the refrigeration apparatus of the sixth aspect, the first refrigerant may include carbon dioxide, which has a high heat dissipation temperature.

[0018] A refrigeration apparatus according to a seventh aspect is the refrigeration apparatus according to any one of the first aspect to the sixth aspect, wherein the second refrigerant includes a hydrocarbon-based refrigerant.

[0019] In the refrigeration apparatus of the seventh aspect, the second refrigerant may include a hydrocarbon-based refrigerant having a low condensation temperature.

[0020] 1 is a schematic configuration diagram of a refrigeration device according to an embodiment of the present disclosure;

[0023] FIG. 1 is a cross-sectional schematic diagram of a heat source unit;

[0024] FIG. 2 is a schematic diagram of a first heat exchanger;

[0025] FIG. 3 is a diagram showing the flow of a first refrigerant in the first heat exchanger and the cascade heat exchanger during heating operation;

[0026] FIG. 4 is a diagram showing the flow of a first refrigerant in the first heat exchanger and the cascade heat exchanger during cooling operation;

[0027] FIG. 5 is a perspective schematic diagram of the first heat exchanger and the second heat exchanger;

[0028] FIG. 6 is a control block diagram of the refrigeration device;

[0029] FIG. 7 is a diagram showing the operation of the refrigeration device during heating operation;

[0030] FIG. 8 is a diagram showing the operation of the refrigeration device during cooling operation;

[0031] FIG. 9 is a schematic diagram of a first heat exchanger of a first modification;

[0032] FIG. 10 is a schematic diagram of a first heat exchanger of a second modification;

[0033]

[0021] (1) Overall Configuration As shown in FIG. 1 , a refrigeration device 1 according to an embodiment of the present disclosure is a device used for heating and cooling the interior of a building or the like by performing a vapor compression refrigeration cycle operation.

[0022] The refrigeration device 1 includes a first circuit 10, a second circuit 20, and a control unit 6. The refrigeration device 1 of this embodiment has a binary circuit consisting of the vapor compression first circuit 10 and the vapor compression second circuit 20, and performs a binary refrigeration cycle.

[0023] A first refrigerant circulates through the first circuit 10. A second refrigerant circulates through the second circuit 20. The first circuit 10 includes a first heat exchanger 13, and the second circuit 20 includes a second heat exchanger 22. The first heat exchanger 13 includes a first heat transfer pipe 131 and a freeze prevention pipe 132 (see FIG. 3 ). The first circuit 10 and the second circuit 20 are thermally connected via a third heat exchanger 30. The third heat exchanger 30 includes a second heat transfer pipe (first flow path 31) through which the first refrigerant flows, and a third heat transfer pipe (second flow path 32) through which the second refrigerant flows.

[0024] The control unit 6 controls the components of the refrigeration device 1 to perform a heating operation for heating an object and a cooling operation for cooling an object.

[0025] During heating operation as a heating operation, the first refrigerant is configured to flow through the second heat transfer pipe, the anti-freeze pipe, and the first heat transfer pipe in this order. During cooling operation as a cooling operation, the first refrigerant is configured to flow from the first heat transfer pipe to the second heat transfer pipe in this order without passing through the anti-freeze pipe.

[0026] The refrigeration system 1 includes a heat source unit 2, a utilization unit 3, and communication pipes 4 and 5. The refrigeration system 1 is configured such that the heat source unit 2 and the utilization unit 3 are connected to each other via the communication pipes 4 and 5.

[0027] (2) Detailed Configuration (2-1) First Circuit The first refrigerant flowing through the first circuit 10 preferably has a critical temperature of less than 45°C. Here, the first refrigerant is non-flammable, non-toxic, or has a GWP of 500 or less. The first refrigerant is, for example, a natural refrigerant, and preferably contains carbon dioxide. The first refrigerant in this embodiment is a single refrigerant of carbon dioxide.

[0028] The first circuit 10 is a main circuit configured to heat or cool indoor air with a first refrigerant.

[0029] The first circuit 10 includes a first compressor 11, a switching mechanism 12, a first heat exchanger 13, a part of the third heat exchanger 30, a first expansion mechanism 14, a fourth heat exchanger 15, and a first accumulator 16.

[0030] The first compressor 11 is a device for compressing the first refrigerant, and is, for example, a positive displacement compressor such as a scroll type whose operating capacity can be varied by inverter control of the compressor motor. In this embodiment, the first compressor 11 discharges the first refrigerant in a supercritical state.

[0031] The switching mechanism 12 is a device that switches between a first state (see the solid line of the switching mechanism 12 in FIG. 1 ) in which the first heat exchanger 13 functions as a radiator for the first refrigerant and the fourth heat exchanger 15 functions as an evaporator for the first refrigerant, and a second state (see the dashed line of the switching mechanism 12 in FIG. 1 ) in which the first heat exchanger 13 functions as an evaporator for the first refrigerant and the fourth heat exchanger 15 functions as a radiator for the first refrigerant. The switching mechanism 12 is, for example, a four-way switching valve. In the first state, the switching mechanism 12 connects the discharge side of the first compressor 11 to the gas side of the first heat exchanger 13 and connects the suction side of the first compressor 11 to the gas side of the fourth heat exchanger 15. In addition, in the second state, the switching mechanism 12 connects the discharge side of the first compressor 11 to the gas side of the fourth heat exchanger 15, and also connects the suction side of the first compressor 11 to the gas side of the first heat exchanger 13.

[0032] The first heat exchanger 13 is a device for exchanging heat between the first refrigerant and the outdoor air without mixing them. In the first heat exchanger 13, the first refrigerant acquires cold or hot heat from the outdoor air. The first heat exchanger 13 is, for example, a microchannel heat exchanger or a fin-and-tube heat exchanger.

[0033] The first expansion mechanism 14 is a device that decompresses the first refrigerant, and is, for example, an electric expansion valve.

[0034] The fourth heat exchanger 15 is a device for exchanging heat between the first refrigerant and the indoor air, and is, for example, a microchannel heat exchanger or a fin-and-tube heat exchanger.

[0035] The first accumulator 16 is provided in the middle of the suction flow path that connects the switching mechanism 12 and the suction side of the first compressor 11. The first accumulator 16 separates the refrigerant that has flowed in into liquid refrigerant and gas refrigerant, and allows the gas refrigerant to flow to the suction side of the first compressor 11.

[0036] (2-2) Second Circuit The second refrigerant flowing through the second circuit 20 has a lower critical temperature than the first refrigerant. The critical temperature of the second refrigerant is preferably 45°C or higher. Here, the second refrigerant is flammable. The second refrigerant is, for example, a hydrocarbon refrigerant such as R1234yf, R1234ze, or R32, and in this embodiment, a single refrigerant, R290, is used.

[0037] The second circuit 20 constitutes a subcooling circuit during cooling operation, and is an assist circuit that assists the capacity of the first circuit 10 during cooling operation.

[0038] The second circuit 20 includes a second compressor 21 , a second heat exchanger 22 , a second expansion mechanism 23 , a second accumulator 24 , and a part of a third heat exchanger 30 .

[0039] The second compressor 21 is a device for compressing the second refrigerant, and is, for example, a positive displacement compressor such as a scroll type whose operating capacity can be varied by inverter controlling the compressor motor.

[0040] The second heat exchanger 22 is a device for exchanging heat between the second refrigerant and the outdoor air without mixing them. In the second heat exchanger 22, the second refrigerant acquires cold or hot heat from the outdoor air. The second heat exchanger 22 is, for example, a microchannel heat exchanger or a fin-and-tube heat exchanger.

[0041] The second circuit 20 has a second flow path 32 of the third heat exchanger 30. The gas side of the second flow path 32 is connected to the second compressor 21, and the liquid side of the second flow path 32 is connected to the second expansion mechanism 23.

[0042] The second expansion mechanism 23 is a device that decompresses the second refrigerant, and is, for example, an electric expansion valve.

[0043] The second accumulator 24 is provided in the middle of the suction flow path that connects the third heat exchanger 30 and the suction side of the second compressor 21. The second accumulator 24 separates the refrigerant that has flowed into it into liquid refrigerant and gas refrigerant, and allows the gas refrigerant to flow to the suction side of the second compressor 21.

[0044] (2-3) Third Heat Exchanger The third heat exchanger 30 is a device for exchanging heat between the first refrigerant and the second refrigerant without mixing them. The third heat exchanger 30 is a cascade heat exchanger, for example, a plate-type heat exchanger. The third heat exchanger 30 has a first flow path 31 belonging to the first circuit 10 and a second flow path 32 belonging to the second circuit 20. In other words, the first flow path 31 constitutes a part of the first circuit 10, and the second flow path 32 constitutes a part of the second circuit 20. In further words, the first flow path 31 of the third heat exchanger 30 is included in the configuration of the first circuit 10, and the second flow path 32 of the third heat exchanger 30 is included in the configuration of the second circuit 20.

[0045] One end of the first flow path 31 is connected to the first heat exchanger 13 , and the other end is connected to the fourth heat exchanger 15 .

[0046] One end of the second flow path 32 is connected to the second compressor 21 , and the other end is connected to the second expansion mechanism 23 .

[0047] When the first heat exchanger 13 of the first circuit 10 is used as a radiator and the second heat exchanger 22 is used as a radiator, the third heat exchanger 30 is intended to supercool the first refrigerant cooled by the first heat exchanger 13, and plays a role of assisting the first circuit 10.

[0048] (2-4) Heat Source Unit In the following description, expressions indicating directions such as "up," "down," "front," "rear," "left," and "right" are used as appropriate, but these indicate the directions when the heat source unit 2 is installed outdoors and in normal use, and do not limit the contents of this disclosure unless otherwise specified. In this embodiment, the up-down direction is the vertical direction, and the left-right direction is the horizontal direction.

[0049] The heat source unit 2 is placed in a space different from the space in which the utilization units 3 are placed. Here, the heat source unit 2 is installed outdoors (on the roof of a building, near the exterior wall surface of a building, etc.).

[0050] As shown in Figure 2, the heat source unit 2 here is a side-blowing type that takes in outdoor air through an opening (intake port O1) on the back of the casing 41 and an opening (intake port O2) on the left side, and blows out the outdoor air that has been heat exchanged in the first heat exchanger 13 and the outdoor air that has been heat exchanged in the second heat exchanger 22 from an opening (outlet port O3) on the front of the casing 41.

[0051] The heat source unit 2 has a part of the first circuit 10 described above, the second circuit 20, a casing 41, a partition plate 42, a fan 43, and a motor 44. Specifically, the heat source unit 2 has the first compressor 11, the switching mechanism 12, the first heat exchanger 13, the first expansion mechanism 14, the first accumulator 16, the second compressor 21, the second heat exchanger 22, the second expansion mechanism 23, the third heat exchanger 30, the fan 43, the motor 44, and the casing 41 and partition plate 42 shown in FIG.

[0052] The casing 41 houses the first compressor 11, the switching mechanism 12, the first heat exchanger 13, the first expansion mechanism 14, the first accumulator 16, the second compressor 21, the second heat exchanger 22, the second expansion mechanism 23, the second accumulator 24, the third heat exchanger 30, a partition plate 42, a fan 43, and a motor 44.

[0053] 2 has a substantially rectangular parallelepiped shape. Specifically, the casing 41 includes a front panel 411, a top panel 412, a bottom panel 413, side panels 414, and a rear panel 415.

[0054] The front plate 411 is a plate-like member that forms the front surface of the casing 41. An air outlet O3 is formed in the front plate 411. The air outlet O3 is an opening for blowing outside air that has been taken into the casing 41 from the outside to the outside of the casing 41.

[0055] The top plate 412 is a plate-like member that forms the upper surface of the casing 41. The bottom plate 413 is a plate-like member that forms the lower surface of the casing 41. The top plate 412 and the bottom plate 413 face each other.

[0056] The side plate 414 is a plate-like member that forms the side surface of the casing 41. An intake port O2 is formed in the side plate 414. In FIG. 2 , the intake port O2 is formed on the left surface. A lower portion of the side plate 414 is fixed to the bottom plate 413.

[0057] The rear plate 415 is a plate-like member that forms the back surface of the casing 41. An intake port O1 is formed in the rear plate 415. A lower portion of the rear plate 415 is fixed to the bottom plate 413.

[0058] The partition plate 42 is a plate-like member that extends in the vertical direction. The lower portion of the partition plate 42 is fixed to the bottom plate 413 of the casing 41.

[0059] The partition plate 42 divides the inside of the casing 41 into a first chamber S1 and a second chamber S2. Each of the first chamber S1 and the second chamber S2 is a space defined by the partition plate 42 and a front plate 411, a top plate 412, a bottom plate 413, a side plate 414, and a rear plate 415 of the casing 41.

[0060] Here, the first chamber S1 is an air supply chamber and an air guide passage through which air drawn in through the air inlets O1 and O2 flows to the air outlet O3. In this embodiment, the first chamber S1 is equipped with the first heat exchanger 13, the second heat exchanger 22, the fan 43, the motor 44, and the like.

[0061] The second chamber S2 is a machinery chamber and contains the first compressor 11, the second compressor 21, the switching mechanism 12, the first expansion mechanism 14, the second expansion mechanism 23, the first accumulator 16, the second accumulator 24, the third heat exchanger 30, and the like.

[0062] Here, the first heat exchanger 13, the second heat exchanger 22, the fan 43, and the motor 44, which are arranged in the first chamber S1, will be mainly described.

[0063] 2, the first heat exchanger 13 is formed in an L-shape when viewed from above. In detail, the first heat exchanger 13 includes a portion extending along the back surface of the casing 41 from near the partition plate 42 to near the left rear corner of the casing 41, a portion curved near the left rear corner of the casing 41, and a portion extending along the side plate 414 from near the left rear corner of the casing 41 to near the left front corner.

[0064] As shown in FIG. 3 , the first heat exchanger 13 includes a first heat transfer pipe 131 , a freeze prevention pipe 132 , fins 133 , piping 134 , a connection portion 135 , and a valve 136 .

[0065] The first heat transfer pipes 131 are arranged in the vertical direction. Specifically, the first heat transfer pipes 131 are arranged at intervals in the vertical direction and extend in a direction perpendicular to the vertical direction.

[0066] The anti-freeze pipe 132 is disposed below the first heat transfer pipe 131. The anti-freeze pipe 132 is disposed at least in the lowest stage of the first heat exchanger 13. In FIG. 3 , the anti-freeze pipe 132 includes a first anti-freeze pipe 132a and a second anti-freeze pipe 132b. The first anti-freeze pipe 132a has one end connected to a first pipe 134a (described later) and the other end connected to a second pipe 134b (described later). The second anti-freeze pipe 132b has one end connected to the first pipe 134a (described later) and the other end connected to a third pipe 134c (described later). The first anti-freeze pipe 132a is disposed in the lowest stage of the first heat exchanger 13, and the second anti-freeze pipe 132b is disposed in the stage one level above the lowest stage. Of the anti-freeze pipes 132, the first anti-freeze pipe 132a is the anti-freeze pipe into which the first refrigerant flows during heating operation.

[0067] The fins 133 are joined to the first heat transfer pipe 131 and the anti-freeze pipe 132. Specifically, the multiple fins 133 are arranged in a direction perpendicular to the up-down direction and extend in the up-down direction.

[0068] The first heat transfer pipe 131 and the fins 133 joined to the first heat transfer pipe 131 constitute a heat transfer section 13A that promotes heat exchange between the first refrigerant flowing inside the first heat transfer pipe 131 and the outdoor air serving as a heat source. The anti-freeze pipe 132 and the fins 133 joined to the anti-freeze pipe 132 constitute an anti-freeze section 13B that suppresses ice growth caused by the freezing of condensed water.

[0069] The pipe 134 is connected to the anti-freeze pipe 132. Here, the pipe 134 includes a first pipe 134a, a second pipe 134b, a third pipe 134c, and a bypass pipe 134d.

[0070] The first pipe 134a connects one end of the first anti-freeze pipe 132a and one end of the second anti-freeze pipe 132b.

[0071] The second pipe 134b is connected to the other end of the first anti-freeze pipe 132a. The second pipe 134b is connected to the first anti-freeze pipe 132a, into which the first refrigerant flows during heating operation. Here, the second pipe 134b connects the first anti-freeze pipe 132a and the first flow path 31 of the third heat exchanger 30.

[0072] The third pipe 134c is connected to the other end of the second anti-freeze pipe 132b. Here, the third pipe 134c connects the second anti-freeze pipe 132b and the first heat transfer pipe 131.

[0073] The bypass pipe 134d bypasses the anti-freeze pipe 132. The bypass pipe 134d branches off from the second pipe 134b toward the first heat transfer pipe 131. Here, the bypass pipe 134d branches off from the second pipe 134b and connects to the lowermost first heat transfer pipe 131 side of the plurality of first heat transfer pipes 131. The bypass pipe 134d also connects the second pipe 134b and the third pipe 134c.

[0074] The connecting portion 135 connects one end and the other end of the first heat transfer tubes 131 that are arranged at intervals in the vertical direction. The connecting portion 135 is, for example, a U-shaped tube or a header.

[0075] The valve 136 is provided in the pipe 134. The valve 136 is at least one of an on-off valve, a three-way valve, and a check valve, and in this embodiment, is a check valve. The valve 136 also includes a first valve 136 a and a second valve 136 b.

[0076] The first valve 136a is provided in the second pipe 134b. The first valve 136a allows the first refrigerant to flow from the first flow path 31 of the third heat exchanger 30 to the first anti-freeze pipe 132a, but prevents the first refrigerant from flowing in the opposite direction.

[0077] The second valve 136b is provided in the bypass pipe 134d. The second valve 136b allows the first refrigerant to flow from the first heat transfer pipe 131 to the first flow path 31 of the third heat exchanger 30, but prevents the first refrigerant from flowing in the opposite direction.

[0078] The pipe 134 and the valve 136 constitute a bypass mechanism for allowing the first refrigerant to bypass the anti-freeze pipe 132 .

[0079] During heating operation, the first refrigerant discharged from the first compressor 11 is configured to flow in this order through the first flow path 31, the anti-freeze pipe 132, and the first heat transfer pipe 131. In Fig. 4, during heating operation, the first refrigerant is configured to flow in this order through the first flow path 31, the second pipe 134b (first valve 136a), the first anti-freeze pipe 132a, the first pipe 134a, the second anti-freeze pipe 132b, the third pipe 134c, and the first heat transfer pipe 131. During heating operation, the first refrigerant discharged from the first compressor 11 does not pass through the bypass pipe 134d.

[0080] Furthermore, during cooling operation, the first refrigerant discharged from the first compressor 11 is configured to flow from the first heat transfer pipe 131 to the first flow path 31 in this order without passing through the anti-freeze pipe 132. In Fig. 5, during cooling operation, the first refrigerant is configured to flow through the first heat transfer pipe 131, the connection part 135, the bypass pipe 134d (second valve 136b), and the first flow path 31 in this order.

[0081] Note that Figures 4 and 5 are diagrams for explaining the flow of the first refrigerant flowing through the first heat exchanger 13 and the third heat exchanger 30, and do not show the vertical positions of the first heat exchanger 13 and the third heat exchanger 30.

[0082] As shown in FIG. 2 , the second heat exchanger 22 is I-shaped in top view. Specifically, the second heat exchanger 22 extends along the back surface of the casing 41 from near the partition plate 42 to the middle of the first chamber S1 in the left-right direction. Thus, the second heat exchanger 22 is disposed on the second chamber S2 side of the first chamber S1. The left-right center of the first chamber S1 and the left-right center of the second heat exchanger 22 are different. The left-right center of the first chamber S1 is the center between the side plate 414 (the left plate in FIG. 2 ) and the partition plate 42, which is located at the same position as the second heat exchanger 22 in the front-rear direction. In this embodiment, the left-right center of the second heat exchanger 22 is located closer to the second chamber S2 (to the right) than the left-right center of the first chamber S1. Therefore, the second heat exchanger 22 does not extend to the left side of the first chamber S1 in the left-right direction.

[0083] The second heat exchanger 22 has a plurality of heat transfer tubes and a plurality of fins joined to the heat transfer tubes.

[0084] In this embodiment, the fins 133 of the first heat exchanger 13 and the fins of the second heat exchanger 22 are spaced apart. In this embodiment, at least one of the fins 133 of the first heat exchanger 13 and the fins of the second heat exchanger 22 is spaced apart, and in this embodiment, all of the fins are spaced apart. Therefore, the fins 133 of the first heat exchanger 13 and the fins of the second heat exchanger 22 are separate members.

[0085] The fan 43 is disposed in the center of the first chamber S1 in the left-right direction, on the front side of the first chamber S1. The fan 43 sends air to the first heat exchanger 13 and the second heat exchanger 22. In this embodiment, the fan 43 flows outdoor air through both the first heat exchanger 13 and the second heat exchanger 22. Here, the fan 43 generates an air flow in which the outdoor air is guided to the first heat exchanger 13 and the second heat exchanger 22, where it exchanges heat with the first refrigerant in the first heat exchanger 13 and the second refrigerant in the second heat exchanger 22, and then discharged to the outside. In this embodiment, the air flow direction F is the first direction in which the first heat exchanger 13 and the second heat exchanger 22 are arranged side by side. The fan 43 is driven by a motor 44.

[0086] 2 and 6 , the second heat exchanger 22 is disposed on the downwind side of the first heat exchanger 13. Specifically, the second heat exchanger 22 is disposed on the downwind side of the first heat exchanger 13 in the flow direction F (see FIG. 2 ) of the air generated by the fan 43. Here, the second heat exchanger 22 is disposed in front of the first heat exchanger 13.

[0087] The first heat exchanger 13 and the second heat exchanger 22 overlap in a first direction. The first direction is a direction perpendicular to a surface of the second heat exchanger 22 facing the first heat exchanger 13. In this embodiment, the first direction is the front-to-rear direction.

[0088] 6 and 7 , the second heat exchanger 22 overlaps with the anti-freeze pipe 132 of the first heat exchanger 13 when viewed in the first direction. As described above, when the first heat exchanger 13 functions as a radiator for the first refrigerant, the temperature of the first refrigerant increases from bottom to top in the first heat exchanger 13. Therefore, the air that exchanges heat with the first refrigerant in the lower region of the first heat exchanger 13 becomes relatively cold. Therefore, by arranging the second heat exchanger 22 on the downwind side of the anti-freeze pipe 132, heat exchange between the air and the second refrigerant in the second heat exchanger 22 can be promoted.

[0089] Similarly, the air that exchanges heat with the first refrigerant flowing through the first heat transfer pipes 131 in the upper region of the first heat exchanger 13 becomes hot. For this reason, it is preferable that the second heat exchanger 22 be arranged so as not to overlap with the upper region of the first heat exchanger 13 when viewed in the first direction. In particular, since the temperature near the inlet of the first refrigerant becomes the highest, it is more preferable that the second heat exchanger 22 be arranged so as not to overlap with the inlet of the first refrigerant. Here, the second heat exchanger 22 is arranged so as not to overlap with the upper right region of the first heat exchanger 13.

[0090] As shown in FIG. 7 , in this embodiment, the entire second heat exchanger 22 is included in the first heat exchanger 13 when viewed in the first direction.

[0091] In addition, in FIG. 2 , the fan 43 overlaps the first heat exchanger 13 and the second heat exchanger 22 when viewed in the first direction.

[0092] (2-5) Utilization Unit The utilization unit 3 shown in Fig. 1 is installed indoors (inside a building). As described above, the utilization unit 3 is connected to the utilization unit 3 via the connecting pipes 4 and 5, and constitutes a part of the first circuit 10.

[0093] The utilization unit 3 has a fourth heat exchanger 15. Here, the utilization unit 3 is installed by being embedded in or suspended from the ceiling of a room in a building or the like, or by being hung on a wall surface of the room.

[0094] (2-6) Connecting Pipes The connecting pipes 4, 5 are refrigerant pipes that are installed on-site when the refrigeration device 1 is installed in an installation location such as a building. One end of the liquid-side connecting pipe 4 is connected to the liquid-side end of the heat source unit 2, and the other end of the connecting pipe 4 is connected to the liquid-side end of the fourth heat exchanger 15 of the utilization unit 3. One end of the gas-side connecting pipe 5 is connected to the gas-side end of the heat source unit 2, and the other end of the connecting pipe 5 is connected to the gas-side end of the fourth heat exchanger 15 of the utilization unit 3.

[0095] (2-7) Control Unit The components of the heat source unit 2 and the utilization unit 3 are controlled by a control unit 6. The control unit 6 is configured by communication connections with the electrical equipment units, etc. provided in the heat source unit 2 and the control boards, etc. provided in the utilization unit 3.

[0096] 8, the control unit 6 controls the components of the heat source unit 2 and the utilization unit 3. In other words, the control unit 6 controls the operation of the refrigeration device 1 as a whole.

[0097] The control unit 6 is realized by a computer. The control unit 6 includes a control and arithmetic unit and a storage device. The control and arithmetic unit can be a processor such as a CPU or a GPU. The control and arithmetic unit reads a program stored in the storage device and performs predetermined image processing and arithmetic processing in accordance with the program. Furthermore, the control and arithmetic unit can write the results of calculations to the storage device and read information stored in the storage device in accordance with the program.

[0098] (3) Operation The operation of the refrigeration device 1 will be described with reference to Figures 1 to 10. The refrigeration device 1 is capable of performing cooling operation to cool indoor air and heating operation to heat indoor air for indoor air conditioning. In cooling operation and heating operation, the operation of the refrigeration device 1 is controlled by the control unit 6.

[0099] (3-1) Heating Operation As shown in Fig. 9, during heating operation, the switching mechanism 12 is switched to the second state (the state in which the switching mechanism 12 is in the dashed line) so that the first heat exchanger 13 functions as an evaporator of the first refrigerant and the fourth heat exchanger 15 functions as a radiator of the first refrigerant. Furthermore, during heating operation, the second compressor 21 is not started, and the second refrigerant is not circulated in the second circuit 20. Here, the second expansion mechanism 23 is fully closed.

[0100] In the first circuit 10 , the first refrigerant in a supercritical state discharged from the first compressor 11 flows out of the heat source unit 2 through the switching mechanism 12 .

[0101] The refrigerant flowing out of the heat source unit 2 flows into the utilization unit 3 via the gas-side connection pipe 5. In the utilization unit 3, the first refrigerant is sent to the fourth heat exchanger 15. The first refrigerant sent to the fourth heat exchanger 15 is cooled by exchanging heat with the indoor air, thereby releasing heat. The first refrigerant that has released heat in the fourth heat exchanger 15 flows out of the utilization unit 3.

[0102] The first refrigerant flowing out of the utilization units 3 flows into the heat source unit 2 via the liquid-side connection pipe 4. In the heat source unit 2, the first refrigerant is sent to the first heat exchanger 13 through the first expansion mechanism 14 and the first flow path 31 of the third heat exchanger 30. The first refrigerant sent to the first heat exchanger 13 is heated and evaporated by heat exchange with outdoor air supplied by the fan 43. The first refrigerant evaporated in the first heat exchanger 13 is sucked back into the first compressor 11 via the switching mechanism 12 and the first accumulator 16.

[0103] The flow of refrigerant in the first heat exchanger 13 during heating operation will now be described primarily with reference to FIG. 4 . As shown in FIG. 4 , the first refrigerant flows out of the first flow path 31 of the third heat exchanger 30 into the second pipe 134b of the first heat exchanger 13, passes through the first valve 136a, and flows into the lowest first anti-freeze pipe 132a. The first refrigerant flowing through the first anti-freeze pipe 132a passes through the first pipe 134a and flows into the second anti-freeze pipe 132b above it. The first refrigerant flowing through the second anti-freeze pipe 132b passes through the third pipe 134c and flows into the lowest first heat transfer pipe 131 without passing through the bypass pipe 134d. The first refrigerant flowing through the first heat transfer pipe 131 exchanges heat with the air, causing a portion of the refrigerant to evaporate. The first refrigerant then flows through the connection 135 into the upper first heat transfer pipe 131. In this manner, the first refrigerant flows sequentially through the first heat transfer pipes 131 and the connecting portions 135 and flows out from the uppermost first heat transfer pipe 131 .

[0104] (3-2) Cooling Operation As shown in FIG. 10, during cooling operation, the switching mechanism 12 is switched to the first state (the state in which the switching mechanism 12 is in the solid line) so that the first heat exchanger 13 functions as a radiator for the first refrigerant and the fourth heat exchanger 15 functions as an evaporator for the first refrigerant.

[0105] In the first circuit 10, the first refrigerant in a supercritical state discharged from the first compressor 11 is sent to the first heat exchanger 13 via the switching mechanism 12. The first refrigerant sent to the first heat exchanger 13 is cooled by exchanging heat with outdoor air supplied by the fan 43, thereby releasing heat. The first refrigerant that has released heat in the first heat exchanger 13 is sent to the first flow path 31 of the third heat exchanger 30. The first refrigerant sent to the first flow path 31 is further cooled in the third heat exchanger 30 by exchanging heat with the second refrigerant flowing through the second flow path 32. The first refrigerant that has been further cooled in the third heat exchanger 30 is decompressed by the first expansion mechanism 14 and then flows out of the heat source unit 2.

[0106] The first refrigerant that flows out of the heat source unit 2 flows into the utilization unit 3 via the liquid side connection pipe 4. In the utilization unit 3, the first refrigerant is sent to the fourth heat exchanger 15. The first refrigerant sent to the fourth heat exchanger 15 is heated through heat exchange with the indoor air and evaporates. The first refrigerant that has evaporated in the fourth heat exchanger 15 flows out of the utilization unit 3.

[0107] The first refrigerant flowing out of the utilization units 3 passes through the gas-side communication pipe 5 and flows into the heat source unit 2. In the heat source unit 2, the first refrigerant passes through the switching mechanism 12 and the first accumulator 16 and is again sucked into the first compressor 11.

[0108] In the second circuit 20, the second refrigerant discharged from the first compressor 11 is sent to the second heat exchanger 22. The second refrigerant sent to the second heat exchanger 22 is cooled by heat exchange with outdoor air supplied by the fan 43, thereby dissipating heat. The second refrigerant that has dissipated heat in the second heat exchanger 22 is decompressed by the second expansion mechanism 23 and then sent to the second flow path 32 of the third heat exchanger 30. The second refrigerant sent to the second flow path 32 is heated and evaporated in the third heat exchanger 30 by heat exchange with the first refrigerant flowing through the first flow path 31. The second refrigerant that has evaporated in the third heat exchanger 30 is drawn back into the second compressor 21 via the second accumulator 24.

[0109] The flow of refrigerant in the first heat exchanger 13 during cooling operation will now be described mainly with reference to FIG. 5 . As shown in FIG. 5 , the first refrigerant discharged from the first compressor 11 flows into the topmost first heat transfer tube 131 of the first heat exchanger 13. The first refrigerant flowing through the first heat transfer tube 131 exchanges heat with the air, partially radiating heat. The first refrigerant then passes through the connecting portion 135 and flows into the next lower first heat transfer tube 131. In this manner, the first refrigerant flows sequentially through the first heat transfer tube 131 and the connecting portion 135, and flows out of the lowest first heat transfer tube 131. This first refrigerant flows into the bypass pipe 134d without passing through the anti-freeze pipe 132, passes through the second valve 136b, and flows out of the first heat exchanger 13. The first refrigerant then flows into the first flow path 31 of the third heat exchanger 30.

[0110] (4) Features (4-1) When a refrigeration system is operated in heating mode under outdoor temperature conditions where the outdoor air temperature is near or below freezing, if the evaporation temperature of the outdoor heat exchanger that serves as the evaporator falls below freezing, there is a problem in that ice buildup from the bottom of the outdoor heat exchanger reduces heat exchange performance. To address this problem, there is a technology that prevents ice buildup by providing an anti-freeze pipe so that a pressure loss occurs at the lowest stage of the outdoor heat exchanger, and by setting the saturation temperature of this anti-freeze pipe above freezing.

[0111] In a subcooling system that includes a first circuit and a second circuit that assists heat dissipation from the first circuit and that performs heat exchange between a first refrigerant in the first circuit and a second refrigerant in the second circuit in a cascade heat exchanger, the cascade heat exchanger that serves as the subcooling unit in the first circuit is located downstream of the outdoor heat exchanger. This causes pressure loss in the freeze prevention pipe to lower the temperature of the second refrigerant flowing into the cascade heat exchanger that constitutes the second circuit. This lowers the evaporation temperature of the second refrigerant, thereby lowering the COP during cooling operation.

[0112] The inventors of the present invention have noticed that when the first refrigerant passes through the freeze prevention pipes during cooling operation, the first refrigerant flows into the cascade heat exchanger in a cooled state, resulting in the adverse effect of supercooling. As a result, they have come up with the idea of ​​a refrigeration system that uses the freeze prevention pipes during heating operation but does not use the freeze prevention pipes during cooling operation.

[0113] Specifically, the refrigeration system 1 according to this embodiment includes a first circuit 10 and a second circuit 20. A first refrigerant circulates through the first circuit 10 and includes a first heat exchanger 13. A second refrigerant circulates through the second circuit 20 and includes a second heat exchanger 22. The first refrigerant and the second refrigerant exchange heat in a cascade heat exchanger, which is a third heat exchanger 30. The first heat exchanger 13 includes a first heat transfer tube 131 and a freeze prevention tube 132. The freeze prevention tube 132 is disposed below the first heat transfer tube 131. The third heat exchanger 30 includes a first flow path 31, which is a second heat transfer tube, and a second flow path 32, which is a third heat transfer tube. The first flow path 31 constitutes a part of the first circuit 10. The second flow path 32 constitutes a part of the second circuit 20. During heating operation as a heating operation, the first refrigerant is configured to be able to flow in this order through the first flow path 31, the anti-freeze pipe 132, and the first heat transfer pipe 131. During cooling operation as a cooling operation, the first refrigerant is configured to be able to flow in this order from the first heat transfer pipe 131 to the first flow path 31 without passing through the anti-freeze pipe 132.

[0114] Here, in a two-cascade refrigeration system including a first circuit 10 and a second circuit 20, during heating operation, the first refrigerant can flow through the antifreeze pipe 132. In this case, pressure loss occurs in the antifreeze pipe 132, allowing the saturation temperature to be above freezing, thereby suppressing ice-up.

[0115] Furthermore, in a two-stage refrigeration system including the first circuit 10 and the second circuit 20, the first refrigerant can bypass the anti-freeze pipe 132 during cooling operation. In this case, an excessive decrease in the temperature of the first refrigerant can be prevented in the first heat exchanger 13. This first refrigerant flows into the third heat exchanger 30 and exchanges heat with the second refrigerant. This prevents a decrease in the evaporation temperature of the second refrigerant in the third heat exchanger 30, thereby promoting heat exchange between the first refrigerant and the second refrigerant. This prevents a decrease in the COP of the refrigeration system 1, thereby suppressing performance degradation.

[0116] (4-2) In the refrigeration system according to the present embodiment, the first heat exchanger 13 preferably further includes a pipe 134 and a valve 136. The pipe 134 is connected to the anti-freeze pipe 132. The valve 136 is provided in the pipe 134. The valve 136 is at least one of an on-off valve, a three-way valve, and a check valve.

[0117] Here, by using a pipe 134 connected to the anti-freeze pipe 132 and at least one valve 136, which is an on-off valve, a three-way valve, and a check valve, provided on this pipe 134, it is possible to easily realize a configuration in which the first refrigerant bypasses the anti-freeze pipe 132 and a configuration in which the first refrigerant flows through the anti-freeze pipe 132.

[0118] Furthermore, when the first valve 136a and the second valve 136b are check valves as in this embodiment, costs can be reduced.

[0119] (4-3) In the refrigeration system 1 according to this embodiment, the pipe 134 preferably includes a bypass pipe 134d. The bypass pipe 134d branches off from a portion (second pipe 134b) connected to the antifreeze pipe 132, into which the first refrigerant flows during heating operation, toward the first heat transfer pipe 131.

[0120] Here, at least one valve 136, which is an on-off valve, a three-way valve, and a check valve, allows the first refrigerant to pass through the bypass pipe 134d, making it easier to realize a configuration in which the first refrigerant bypasses the anti-freeze pipe 132.

[0121] (4-4) In the refrigeration device 1 according to this embodiment, the operation of the second circuit 20 is preferably stopped during the heating operation as the heating operation.

[0122] In this way, if the performance does not improve even if the second circuit 20 is operated during the heating operation, it is possible to not use the second circuit 20. In this case, it is possible to suppress a decrease in efficiency during the heating operation.

[0123] (4-5) In the refrigeration system 1 according to this embodiment, the second heat exchanger 22 is preferably disposed on the downwind side of the first heat exchanger 13. The first heat exchanger 13 and the second heat exchanger 22 are disposed in the first direction. The second heat exchanger 22 overlaps with the anti-freeze pipe 132 when viewed in the first direction.

[0124] During cooling operation, the first refrigerant does not flow through the anti-freeze pipe 132, or the first refrigerant flowing through the anti-freeze pipe 132 is at a lower temperature than the first refrigerant flowing through the first heat transfer pipe 131. Therefore, the air that has passed through the anti-freeze pipe 132 is at a relatively low temperature. Here, since the second heat exchanger 22 is disposed on the downwind side of the anti-freeze pipe 132, a decrease in the heat exchange efficiency between the air that has passed through the first heat exchanger 13 and the second refrigerant in the second heat exchanger 22 can be suppressed.

[0125] (4-6) In the refrigeration device 1 according to this embodiment, the first refrigerant preferably contains carbon dioxide refrigerant. In this way, a first refrigerant containing carbon dioxide, which has a high heat dissipation temperature, can be used.

[0126] (4-7) In the refrigeration device 1 according to this embodiment, the second refrigerant preferably contains a hydrocarbon-based refrigerant. In this manner, a second refrigerant containing a hydrocarbon-based refrigerant with a low condensation temperature can be used.

[0127] (5) Modifications (5-1) Modification 1 In the above embodiment, the valve 136 provided in the pipe 134 of the first heat exchanger 13 is a check valve, but this is not limiting. In this modification, as shown in FIG. 11 , the valve 136 is an on-off valve.

[0128] Specifically, the valve 136 includes a third valve 136c and a fourth valve 136d. The third valve 136c is provided in the second pipe 134b. The fourth valve 136d is provided in the bypass pipe 134d. The third valve 136c and the fourth valve 136d are, for example, motor-operated valves or solenoid valves.

[0129] During heating operation, the control unit 6 opens the third valve 136c and closes the fourth valve 136d. As a result, similar to the above embodiment, during heating operation, the first refrigerant flows through the first flow path 31 of the third heat exchanger 30, the second pipe 134b (third valve 136c), the first anti-freeze pipe 132a, the first pipe 134a, the second anti-freeze pipe 132b, the third pipe 134c, and the first heat transfer pipe 131 in this order.

[0130] Furthermore, in the above embodiment, the first refrigerant passes through the anti-freeze pipe 132 during heating operation, but this is not limited to this. In the refrigeration apparatus disclosed herein, the first refrigerant basically passes through the anti-freeze pipe 132 during heating operation, but may bypass the anti-freeze pipe 132. In this modification, the first refrigerant basically passes through the anti-freeze pipe 132 during heating operation, but may bypass the anti-freeze pipe 132 in some cases. In this case, the control unit 6 closes the third valve 136c and opens the fourth valve 136d. As a result, during heating operation, the first refrigerant flows through the first flow path 31 of the third heat exchanger 30, the bypass pipe 134d (fourth valve 136d), and the first heat transfer pipe 131 in this order.

[0131] As described above, insufficient capacity of the third valve 136c is one of the conditions for preventing the flow of air from passing through the anti-freeze pipe 132 during heating operation. For example, if a decrease in performance occurs due to pressure loss in the anti-freeze pipe 132 even when the solenoid valve selected as the third valve 136c is fully opened, the control unit 6 controls the third valve 136c and the fourth valve 136d so that the flow of air does not pass through the anti-freeze pipe 132 during heating operation.

[0132] On the other hand, during cooling operation, the control unit 6 closes the third valve 136c and opens the fourth valve 136d, so that during cooling operation, the first refrigerant flows through the first heat transfer pipe 131, the bypass pipe 134d (the fourth valve 136d), and the first flow path 31 of the third heat exchanger 30 in this order, as in the above embodiment.

[0133] In the above embodiment, the first refrigerant does not pass through the anti-freeze pipe during cooling operation, but this is not limited to this. In the refrigeration system 1 of the present disclosure, the first refrigerant basically bypasses the anti-freeze pipe 132 during cooling operation, but may pass through the anti-freeze pipe 132. In this case, the control unit 6 opens the third valve 136c and closes the fourth valve 136d. As a result, during cooling operation, the first refrigerant flows through the first heat transfer pipe 131, the third pipe 134c, the second anti-freeze pipe 132b, the first pipe 134a, the first anti-freeze pipe 132a, the second pipe 134b (the third valve 136c), and the first flow path 31 of the third heat exchanger 30 in this order.

[0134] As described above, one of the conditions for passing through the anti-freeze pipe 132 during cooling operation is that the required load is low.

[0135] Furthermore, the refrigeration system of this modified example is capable of defrosting operation. During defrosting operation, the control unit 6 opens the third valve 136c and closes the fourth valve 136d. As a result, during defrosting operation, the first refrigerant flows through the first heat transfer pipe 131, the third pipe 134c, the second anti-freeze pipe 132b, the first pipe 134a, the first anti-freeze pipe 132a, the second pipe 134b (the third valve 136c), and the first flow path 31 of the third heat exchanger 30 in this order.

[0136] When the third valve 136c and the fourth valve 136d are open / close valves as in this modified example, it is possible to select whether or not the air passes through the anti-freeze pipe 132 during heating and cooling operation, and defrost operation is also possible.

[0137] (5-2) Modification 2 In the above embodiment, the valve 136 provided in the pipe 134 of the first heat exchanger 13 is a check valve, but this is not limiting. In this modification, as shown in FIG. 12 , the valve 136 is a three-way valve.

[0138] Specifically, the fifth valve 136e, which is a three-way valve, is provided at one end of the bypass pipe 134d and switches between a third state (see the solid line of the fifth valve 136e in FIG. 12 ) in which the first heat transfer pipe 131 and the freeze prevention pipe 132 are connected, and a fourth state (see the dashed line of the fifth valve 136e in FIG. 12 ) in which the first heat transfer pipe 131 and the bypass pipe 134d are connected.

[0139] During heating operation, the control unit 6 switches the fifth valve 136e to the third state. As a result, similar to the above embodiment, during heating operation, the first refrigerant flows through the first flow path 31 of the third heat exchanger 30, the second pipe 134b, the first anti-freeze pipe 132a, the first pipe 134a, the second anti-freeze pipe 132b, the third pipe 134c, the fifth valve 136e, and the first heat transfer pipe 131 in this order.

[0140] During cooling operation, the control unit 6 switches the fifth valve 136e to the fourth state. As a result, during cooling operation, similarly to the above embodiment, the first refrigerant flows through the first heat transfer pipe 131, the fifth valve 136e, the bypass pipe 134d, and the first flow path 31 of the third heat exchanger 30 in this order.

[0141] During defrosting operation, the control unit 6 switches the fifth valve 136e to the third state, causing the first refrigerant to flow through the first heat transfer pipe 131, the fifth valve 136e, the third pipe 134c, the second anti-freeze pipe 132b, the first pipe 134a, the first anti-freeze pipe 132a, the second pipe, and the first flow path 31 of the third heat exchanger 30 in this order.

[0142] The fifth valve 136e may be provided at the other end of the bypass pipe 134d.

[0143] When the fifth valve 136e is a three-way valve as in this modified example, it is possible to select whether or not the air passes through the anti-freeze pipe 132 during heating and cooling operation, and defrost operation is also possible.

[0144] (5-3) Modification 3 In the above embodiment, the second heat exchanger 22 does not extend to the left side of the first chamber S1 in the left-right direction to its full extent, but this is not limiting. In this modification, the left-right width of the second heat exchanger 22 has a maximum length.

[0145] Specifically, the second heat exchanger 22 extends to face the portion of the first heat exchanger 13 that extends from the partition plate 42 to near the left rear corner of the casing 41. The second heat exchanger 22 extends in the left-right direction to an extent that it does not come into contact with the first heat exchanger 13 that extends from the left rear corner of the casing 41 to near the left front corner.

[0146] (5-4) Modification 4 In the above embodiment, the entire second heat exchanger 22 is encompassed by the first heat exchanger 13, but a portion of the second heat exchanger 22 may overlap the first heat exchanger 13 when viewed in the first direction.

[0147] (5-5) Modification 5 In the above embodiment, the fins 133 of the first heat exchanger 13 and the fins of the second heat exchanger 22 are separate members, but this is not limiting. In this modification, the fins 133 of the first heat exchanger 13 and the fins of the second heat exchanger 22 are integral with each other.

[0148] Specifically, a portion of the fins 133 of the first heat exchanger 13 is connected to at least a portion of the fins of the second heat exchanger 22. The fins 133 of the first heat exchanger 13 and the fins of the second heat exchanger 22 may have holes formed therein, such as perforations.

[0149] (5-6) Modification 6 In the above embodiment, the common fan 43 sends air to the first heat exchanger 13 and the second heat exchanger 22. However, this is not limiting. In this modification, a fan that sends air to the first heat exchanger 13 and a fan that sends air to the second heat exchanger 22 are provided separately.

[0150] (5-7) Modification 7 In the above embodiment, a side-blowing type heat source unit has been described as an example, but this is not limiting. The heat source unit of this modification is an upward-blowing type. In an upward-blowing type, a fan 43 is disposed above the first heat exchanger 13 and the second heat exchanger 22. When the fan 43 is operated, air is taken in through an opening provided on the side of the casing 41 and passes through the first heat exchanger 13 and the second heat exchanger 22. The air that has exchanged heat with the first refrigerant in the first heat exchanger 13 and the air that has exchanged heat with the second refrigerant in the second heat exchanger 22 is blown upward from an opening provided on the top surface of the casing 41. Therefore, the air flow direction F generated by the fan 43 includes the first direction in which the first heat exchanger 13 and the second heat exchanger 22 are stacked.

[0151] (5-8) Modification 8 In the above embodiment, the operation of the second circuit 20 is stopped during heating operation, but this is not limiting. The refrigeration apparatus of the present disclosure may operate the second circuit 20 during heating operation.

[0152] In the above embodiment, the second circuit 20 is operated during cooling operation, but this is not limiting. The refrigeration apparatus of the present disclosure may stop operation of the second circuit 20 during cooling operation.

[0153] (5-9) Modification 9 In the above embodiment, the refrigeration system 1 is described as an example in which one utilization unit 3 is connected to one heat source unit 2. However, the present modification is not limited to this. In the refrigeration system of this modification, multiple utilization units are connected to one heat source unit.

[0154] (5-10) Modification 10 In the above embodiment, the refrigeration apparatus 1 that performs cooling operation and heating operation has been described as an example, but is not limited to this. The refrigeration apparatus of the present disclosure may also perform a dehumidifying operation.

[0155] (5-11) Modification 11 In the above embodiment, the refrigeration device is applied to an air conditioner, but is not limited to this. The refrigeration device of the present disclosure performs heating operation and cooling operation, and therefore may be applied to refrigeration devices such as water heaters, floor heating systems, and refrigerators.

[0156] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims.

[0157] DESCRIPTION OF SYMBOLS 1: Refrigeration device 2: Heat source unit 3: Utilization unit 10: First circuit 13: First heat exchanger 20: Second circuit 22: Second heat exchanger 30: Third heat exchanger (cascade heat exchanger) 31: First flow path (second heat transfer tube) 32: Second flow path (third heat transfer tube) 131: First heat transfer tube 132, 132a, 132b: Anti-freeze tube 134, 134a, 134b, 134c, 134d: Piping 134d: Bypass pipe 136, 136a, 136b, 136c, 136e: Valve

[0158] Japanese Patent Application Laid-Open No. 2007-232274

Claims

1. A refrigeration system (1) comprising a first circuit (10) through which a first refrigerant circulates and which has a first heat exchanger (13), and a second circuit (20) through which a second refrigerant circulates and which has a second heat exchanger (22), wherein heat is exchanged between the first refrigerant and the second refrigerant in a cascade heat exchanger (30), wherein the first heat exchanger includes a first heat transfer tube (131) and a freeze prevention tube (132) arranged below the first heat transfer tube, and the cascade heat exchanger includes a second heat transfer tube (31) which constitutes part of the first circuit and a third heat transfer tube (32) which constitutes part of the second circuit, wherein during heating operation, the first refrigerant is configured to be able to flow through the second heat transfer tube, the freeze prevention tube, and the first heat transfer tube in that order, and during cooling operation, the refrigeration system is configured to be able to flow from the first heat transfer tube to the second heat transfer tube in that order without passing through the freeze prevention tube.

2. The refrigeration system according to claim 1, wherein the first heat exchanger further includes a pipe (134) connected to the anti-freeze pipe, and a valve (136) provided in the pipe, and the valve is at least one of an on-off valve, a three-way valve, and a check valve.

3. The refrigeration device according to claim 2, wherein the piping has a bypass pipe (134d) branching off from a portion (134b) connected to the anti-freeze pipe into which the first refrigerant flows during the heating operation to the first heat transfer pipe side.

4. The refrigeration device according to any one of claims 1 to 3, wherein the operation of the second circuit is stopped during heating operation.

5. A refrigeration device according to any one of claims 1 to 4, wherein the second heat exchanger is arranged on the downwind side of the first heat exchanger, the first heat exchanger and the second heat exchanger are arranged in a first direction, and the second heat exchanger overlaps with the anti-freeze pipe when viewed in the first direction.

6. The refrigeration device according to any one of claims 1 to 5, wherein the first refrigerant includes a carbon dioxide refrigerant.

7. The refrigeration device according to any one of claims 1 to 6, wherein the second refrigerant includes a hydrocarbon-based refrigerant.

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