Refrigeration cycle system

Abstract

Heat exchange efficiency of a cascade heat exchanger is inhibited from decreasing. A primary-side refrigerant circuit (5a) is a circuit for circulating a primary-side refrigerant, and has a primary-side compressor (71), a cascade heat exchanger (35), and a primary-side heat exchanger (74). A secondary-side refrigerant circuit (10) is a circuit for circulating a secondary-side refrigerant, and has a secondary-side compressor (21), the cascade heat exchanger (35), and a utilization-side heat exchanger (52a, 52b, 52c). The primary-side refrigerant circuit (5a) has a first connection pipe (115) connecting the cascade heat exchanger (35) and the primary-side heat exchanger (74), a primary-side first communication pipe (111), and a liquid connection pipe (126). The primary-side compressor (71) has a primary-side suction flow path (125). The primary-side refrigerant circuit (5a) has a primary-side subcooling circuit (104) connecting the liquid connection pipe (126) and the primary-side suction flow path (125). The primary-side refrigerant circuit (5a) has a primary-side subcooling expansion valve (104a) provided in the primary-side subcooling circuit (104). When the cascade heat exchanger (35) functions as a radiator for the primary-side refrigerant and functions as an evaporator for the secondary-side refrigerant, and when an index related to a degree of subcooling of the primary-side refrigerant at an outlet of the cascade heat exchanger (35) satisfies a prescribed start condition, the primary-side subcooling expansion valve (104a) is opened.

Description

TECHNICAL FIELD

[0001] The present application relates to a refrigeration cycle system. BACKGROUND

[0002] In the past, for example, a binary refrigeration device that connects a primary-side refrigerant circuit and a secondary-side refrigerant circuit via a cascade heat exchanger is known, like the refrigeration device described in Patent Literature 1 (International Publication No. 2018 / 235832). SUMMARY

[0003] PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] The cascade heat exchanger of the binary refrigeration device described above tends to be small in heat exchanger volume compared to an air heat exchanger that performs heat exchange between a refrigerant and air. Therefore, in the cascade heat exchanger, if the degree of supercooling of the refrigerant of the radiator becomes large due to a load variation of the evaporator, the proportion of the region in which liquid refrigerant exists with respect to the entire heat exchanger volume becomes large, and the heat exchange rate between the refrigerants in the cascade heat exchanger can decrease.

[0005] MEANS OF SOLVING THE PROBLEMS

[0006] The refrigeration cycle system according to a first aspect includes a first circuit and a second circuit. The first circuit is a circuit in which a first refrigerant circulates. The first circuit has a first compressor, a cascade heat exchanger, and a first heat exchanger. The second circuit is a circuit in which a second refrigerant circulates. The second circuit has a second compressor, the cascade heat exchanger, and a second heat exchanger. The first circuit has a first flow path, a suction flow path, a bypass circuit, and a control valve. The first flow path connects the cascade heat exchanger and the first heat exchanger. The suction flow path is a flow path that extends from a suction side of the first compressor. The bypass circuit connects the first flow path and the suction flow path. The control valve is provided to the bypass circuit. When the cascade heat exchanger functions as a radiator of the first refrigerant and functions as an evaporator of the second refrigerant, the control valve is opened in a case where an index related to the degree of supercooling of the first refrigerant at an outlet of the cascade heat exchanger satisfies a prescribed first condition.

[0007] Here, the cascade heat exchanger can be used to perform heat exchange between the first refrigerant and the second refrigerant.

[0008] Further, the control valve can be a valve that switches between an open state and a closed state, or can be a valve that can adjust the degree of opening.

[0009] In the refrigeration cycle system, the control valve is opened when the prescribed first condition is satisfied, and thus a state in which the proportion of the region in which the first refrigerant in a liquid state exists in the cascade heat exchanger is large is easily eliminated. Thus, it is possible to suppress a decrease in heat exchange efficiency in the cascade heat exchanger.

[0010] The second viewpoint's refrigeration cycle system, on the basis of the first viewpoint's refrigeration cycle system, satisfies the first condition in a case where at least any one of the following is satisfied: (A) a value obtained by subtracting the temperature of the first refrigerant flowing out of the cascade heat exchanger from the condensing temperature of the first refrigerant in the first circuit is a prescribed value or more; (B) a value obtained by subtracting the pressure of the low-pressure refrigerant in the second circuit from the pressure of the high-pressure refrigerant in the first circuit is a prescribed value or more; (C) a value obtained by subtracting the evaporation temperature of the second refrigerant in the second circuit from the condensing temperature of the first refrigerant in the first circuit is a prescribed value or more; and (D) a value obtained by subtracting the temperature of the second refrigerant flowing into the cascade heat exchanger from the condensing temperature of the first refrigerant in the first circuit is a prescribed value or more.

[0011] The third viewpoint's refrigeration cycle system, on the basis of the second viewpoint's refrigeration cycle system, has a temperature-pressure characteristic of the first refrigerant different from a temperature-pressure characteristic of the second refrigerant. The first condition is judged on the basis of a temperature difference between a temperature of the first refrigerant grasped from the pressure of the first refrigerant in the cascade heat exchanger and a temperature of the second refrigerant grasped from the pressure of the second refrigerant in the cascade heat exchanger.

[0012] In the refrigeration cycle system, even in a case where stable judgment of the first condition using pressure is difficult to achieve, by using a temperature converted from the pressure to judge the first condition, the judgment of the decrease in the heat exchange efficiency in the cascade heat exchanger can be further highly accurately performed.

[0013] The fourth viewpoint's refrigeration cycle system, on the basis of the first viewpoint's refrigeration cycle system, satisfies the first condition in a case where at least any one of the following is satisfied: (a) a difference between the temperature of the first refrigerant flowing out of the cascade heat exchanger and the temperature of the second refrigerant flowing into the cascade heat exchanger is a prescribed value or less; (b) a superheat degree of the second refrigerant sucked into the second compressor is a prescribed value or less; and (c) an opening degree of the second expansion valve is smaller than a prescribed opening degree. Here, regarding (c), the second circuit has the second expansion valve between the second heat exchanger and the cascade heat exchanger, and the valve opening degree of the second expansion valve is changed in accordance with the superheat degree of the second refrigerant sucked into the second compressor.

[0014] The fifth viewpoint's refrigeration cycle system, on the basis of the refrigeration cycle system of any one of the first to fourth viewpoints, has a tank in the first circuit. The suction flow path includes a first suction flow path and a second suction flow path. The first suction flow path, the tank, the second suction flow path, and the first compressor are connected in this order. The bypass circuit is connected to the first suction flow path.

[0015] In the refrigeration cycle system, even in a case where the first refrigerant flows in the bypass circuit, since the first refrigerant is sucked into the first compressor via the tank, it is possible to suppress the first compressor from sucking the first refrigerant in a liquid state.

[0016] The refrigeration cycle system of the sixth aspect is based on the refrigeration cycle system of any one of the first to fifth aspects, and in a case where the first condition is satisfied, the control valve is fully opened.

[0017] In the refrigeration cycle system, it is possible to quickly improve the heat exchange efficiency in the cascade heat exchanger.

[0018] The refrigeration cycle system of the seventh aspect is based on the refrigeration cycle system of any one of the first to sixth aspects, and in a case where the first condition is satisfied, the rotation speed of the second compressor is reduced.

[0019] In the refrigeration cycle system, it is possible to suppress the condensation of the first refrigerant in the cascade heat exchanger, and suppress an increase in the proportion of the first refrigerant in a liquid state in the cascade heat exchanger.

[0020] The refrigeration cycle system of the eighth aspect is based on the refrigeration cycle system of any one of the first to seventh aspects, and further includes a first control unit that controls the first circuit, and a second control unit that controls the second circuit.

[0021] In the refrigeration cycle system, it is possible for the first control unit to control the first circuit, and for the second control unit to control the second circuit.

[0022] The refrigeration cycle system of the ninth aspect is based on the refrigeration cycle system of the eighth aspect, and in a case where the first condition is satisfied, the second control unit outputs a control instruction to the control valve. In a case where the first condition is not satisfied, the first control unit outputs a control instruction to the control valve. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic configuration diagram of a refrigeration cycle system.

[0024] Figure 2 is a schematic functional configuration block diagram of a refrigeration cycle system.

[0025] Figure 3 is a diagram showing the operation (flow of refrigerant) in a refrigeration operation of a refrigeration cycle system.

[0026] Figure 4 is a diagram showing the operation (flow of refrigerant) in a heating operation of a refrigeration cycle system.

[0027] Figure 5is a view showing the operation (flow of refrigerant) in the simultaneous cooling and heating operation (heating main body) of the refrigeration cycle system.

[0028] Figure 6 is a view showing the operation (flow of refrigerant) in the simultaneous cooling and heating operation (heating main body) of the refrigeration cycle system.

[0029] Figure 7 is a flowchart of the remaining refrigerant control.

[0030] Figure 8 is a view showing the operation (flow of refrigerant) in the remaining refrigerant control of the refrigeration cycle system.

[0031] Figure 9 is a schematic configuration view of the refrigeration cycle system of the other embodiment A.

[0032] Figure 10 is a schematic configuration view of the refrigeration cycle system of the other embodiment B. DETAILED DESCRIPTION

[0033] (1) Structure of refrigeration cycle system

[0034] Figure 1 is a schematic configuration view of the refrigeration cycle system 1. Figure 2 is a schematic functional configuration block diagram of the refrigeration cycle system.

[0035] The refrigeration cycle system 1 is an apparatus that operates by performing a vapor compression type refrigeration cycle for refrigeration, heating of an indoor space of a building or the like.

[0036] The refrigeration cycle system 1 has a binary refrigerant circuit composed of a vapor compression type primary side refrigerant circuit 5a (corresponding to a first circuit) and a vapor compression type secondary side refrigerant circuit 10 (corresponding to a second circuit), and performs a binary refrigeration cycle. As a refrigerant, for example, R32 (corresponding to a first refrigerant) or the like is enclosed in the primary side refrigerant circuit 5a. As a refrigerant, for example, carbon dioxide (corresponding to a second refrigerant) is enclosed in the secondary side refrigerant circuit 10. The primary side refrigerant circuit 5a and the secondary side refrigerant circuit 10 are thermally connected via a cascade heat exchanger 35 described below.

[0037] The refrigeration cycle system 1 is configured in such a manner that the primary-side unit 5, the heat-source unit 2, the plurality of branch units 6a, 6b, 6c, and the plurality of utilization units 3a, 3b, 3c are connected to one another via pipes. The primary-side unit 5 and the heat-source unit 2 are connected by a primary-side first communication pipe 111 and a primary-side second communication pipe 112. The heat-source unit 2 and the plurality of branch units 6a, 6b, 6c are connected by a secondary-side second communication pipe 9, a secondary-side first communication pipe 8, and a secondary-side third communication pipe 7. The plurality of branch units 6a, 6b, 6c and the plurality of utilization units 3a, 3b, 3c are connected by first branch connection pipes 15a, 15b, 15c and second branch connection pipes 16a, 16b, 16c. In the present embodiment, the primary-side unit 5 is one. In the present embodiment, the heat-source unit 2 is one. In the present embodiment, the plurality of utilization units 3a, 3b, 3c are a first utilization unit 3a, a second utilization unit 3b, and a third utilization unit 3c. In the present embodiment, the plurality of branch units 6a, 6b, 6c are a first branch unit 6a, a second branch unit 6b, and a third branch unit 6c.

[0038] Also, in the refrigeration cycle system 1, each of the utilization units 3a, 3b, 3c is capable of performing refrigeration operation or heating operation individually, and is configured to be capable of performing heat recovery between the utilization units by transporting refrigerant from the utilization unit performing heating operation to the utilization unit performing refrigeration operation. Specifically, in the present embodiment, heat recovery is performed by performing refrigeration-main operation and heating-main operation in which refrigeration operation and heating operation are performed simultaneously. Further, in the refrigeration cycle system 1, the heat-source unit 2 is configured to balance a heat load in accordance with a total heat load of the plurality of utilization units 3a, 3b, 3c, which also takes into account the above-described heat recovery (refrigeration-main operation and heating-main operation).

[0039] (2) Primary-side refrigerant circuit

[0040] The primary refrigerant circuit 5a includes a primary compressor 71 (equivalent to a first compressor), a primary switching mechanism 72, a primary heat exchanger 74 (equivalent to a first heat exchanger), a liquid connection pipe 126 (equivalent to a part of the first flow path), a primary first expansion valve 76, a primary subcooling heat exchanger 103, a primary subcooling circuit 104 (equivalent to a bypass circuit), a primary subcooling expansion valve 104a (equivalent to a control valve), a first liquid shut-off valve 108, a primary first connecting pipe 111 (equivalent to a part of the first flow path), a second liquid shut-off valve 106, a first connecting pipe 115 (equivalent to a part of the first flow path), a primary second expansion valve 102, a cascaded heat exchanger 35 shared with the secondary refrigerant circuit 10, a second connecting pipe 113, a second gas shut-off valve 107, a primary second connecting pipe 112, a first gas shut-off valve 109, a primary suction flow path 125 (equivalent to a suction flow path), and a primary storage tank 105 (equivalent to a storage tank).

[0041] The primary side compressor 71 is a device for compressing the primary side refrigerant, and is, for example, a scroll-type positive displacement compressor whose operating capacity can be varied by inverter control of the compressor motor 71a.

[0042] The primary side storage tank 105 is located in the middle of the primary side suction flow path 125 that connects the primary side switching mechanism 72 and the suction side of the primary side compressor 71.

[0043] The primary side suction flow path 125 has: a first suction flow path 125a connecting the primary side switching mechanism 72 and the primary side storage tank 105; and a second suction flow path 125b connecting the primary side storage tank 105 and the suction side of the primary side compressor 71.

[0044] When the cascaded heat exchanger 35 functions as an evaporator for the primary-side refrigerant, the primary-side switching mechanism 72 changes to a fifth connection state that connects the suction side of the primary-side compressor 71 and the gas side of the primary-side flow path 35b of the cascaded heat exchanger 35 (see reference). Figure 1 (Solid line of the primary-side switching mechanism 72). Furthermore, when the cascaded heat exchanger 35 functions as a radiator for the primary-side refrigerant, the primary-side switching mechanism 72 changes to a sixth connection state, connecting the discharge side of the primary-side compressor 71 and the gas side of the primary-side flow path 35b of the cascaded heat exchanger 35 (see reference). Figure 1 (The primary-side switching mechanism 72 is indicated by the dashed line). Thus, the primary-side switching mechanism 72 is a device capable of switching the flow path of the refrigerant within the primary-side refrigerant circuit 5a, and is, for example, constituted by a four-way switching valve. Furthermore, by changing the switching state of the primary-side switching mechanism 72, the cascaded heat exchanger 35 can function as an evaporator or radiator for the primary-side refrigerant.

[0045] The cascade heat exchanger 35 is a device for performing heat exchange between a refrigerant such as R32 as a primary-side refrigerant and a refrigerant such as carbon dioxide as a secondary-side refrigerant without mixing each other. The cascade heat exchanger 35 is constituted by, for example, a plate heat exchanger. The cascade heat exchanger 35 has a secondary-side flow path 35a belonging to the secondary-side refrigerant circuit 10 and a primary-side flow path 35b belonging to the primary-side refrigerant circuit 5a. The gas side of the secondary-side flow path 35a is connected with the secondary-side switching mechanism 22 via the third heat source pipe 25, and the liquid side of the secondary-side flow path 35a is connected with the heat source-side expansion valve 36 via the fourth heat source pipe 26. The gas side of the primary-side flow path 35b is connected with the primary-side compressor 71 via the second connection pipe 113, the second gas shut-off valve 107, the primary-side second communication pipe 112, the first gas shut-off valve 109, the primary-side switching mechanism 72, the first suction flow path 125a, the primary-side accumulator 105, the second suction flow path 125b, and the primary-side second expansion valve 102 provided to the first connection pipe 115 is connected with the liquid side of the primary-side flow path 35b.

[0046] The primary-side heat exchanger 74 is a device for performing heat exchange between the primary-side refrigerant and the outdoor air. The gas side of the primary-side heat exchanger 74 is connected with a pipe extending from the primary-side switching mechanism 72. The liquid side of the primary-side heat exchanger 74 is connected with the first liquid shut-off valve 108 through a liquid connection pipe 126. The primary-side heat exchanger 74 is constituted by, for example, a finned tube heat exchanger constituted by a plurality of heat transfer pipes and fins.

[0047] The liquid connection pipe 126 connects the liquid side end portion of the primary-side heat exchanger 74 with the first liquid shut-off valve 108, and has a first liquid connection pipe 126a and a second liquid connection pipe 126b. The first liquid connection pipe 126a extends from the liquid side end portion of the primary-side heat exchanger 74 to the primary-side first expansion valve 76. The second liquid connection pipe 126b extends from the primary-side first expansion valve 76 through the primary-side subcooling heat exchanger 103 to the first liquid shut-off valve 108.

[0048] The primary-side first expansion valve 76 is provided to a portion of the liquid connection pipe 126 between the liquid side of the primary-side heat exchanger 74 and the primary-side subcooling heat exchanger 103. The primary-side first expansion valve 76 is an electric expansion valve capable of opening degree adjustment, and performs adjustment of the flow rate of the primary-side refrigerant flowing in the liquid connection pipe 126 of the primary-side refrigerant circuit 5a and the like.

[0049] The primary-side subcooling circuit 104 branches from between the primary-side first expansion valve 76 and the primary-side subcooling heat exchanger 103 in the liquid connection pipe 126 and is connected to a first suction flow path 125a in the primary-side suction flow path 125. A primary-side subcooling expansion valve 104a is provided in the primary-side subcooling circuit 104 at an upstream side than the primary-side subcooling heat exchanger 103. The primary-side subcooling expansion valve 104a is an electric expansion valve capable of opening degree adjustment, and performs adjustment of the flow rate of the primary-side refrigerant flowing in the primary-side subcooling circuit 104 and the like.

[0050] The primary-side subcooling heat exchanger 103 is a heat exchanger that exchanges heat between the refrigerant flowing from the primary-side first expansion valve 76 toward the first liquid shut-off valve 108 and the refrigerant that has been depressurized in the primary-side subcooling expansion valve 104a in the primary-side subcooling circuit 104.

[0051] The primary-side first communication pipe 111 is a pipe that connects the first liquid shut-off valve 108 and the second liquid shut-off valve 106, and connects the primary-side unit 5 and the heat source unit 2.

[0052] The primary-side second communication pipe 112 is a pipe that connects the first gas shut-off valve 109 and the second gas shut-off valve 107, and connects the primary-side unit 5 and the heat source unit 2.

[0053] The first connection pipe 115 is a pipe that connects the second liquid shut-off valve 106 and the liquid side of the primary-side flow path 35b of the cascade heat exchanger 35, and is provided in the heat source unit 2.

[0054] The primary-side second expansion valve 102 is an electric expansion valve capable of opening degree adjustment, and is provided in the first connection pipe 115, and performs adjustment of the flow rate of the primary-side refrigerant flowing in the first connection pipe 115 and the like.

[0055] The second connection pipe 113 is a pipe that connects the gas side of the primary-side flow path 35b of the cascade heat exchanger 35 and the second gas shut-off valve 107, and is provided in the heat source unit 2.

[0056] The first gas shut-off valve 109 is provided between the primary-side second communication pipe 112 and the primary-side switching mechanism 72.

[0057] (3) Secondary-side refrigerant circuit

[0058] The secondary-side refrigerant circuit 10 is configured in a manner that the heat-source circuit 12, the branch circuits 14a, 14b, 14c, and the utilization circuits 13a, 13b, 13c are connected to each other.

[0059] According to the operating state, either one of the refrigerant in the gas-liquid two-phase state and the refrigerant in the gas state flows in the secondary-side first communicating pipe 8. In addition, according to the kind of the second refrigerant, the refrigerant in the supercritical state is caused to flow in the secondary-side first communicating pipe 8 in correspondence with the operating state. According to the operating state, either one of the refrigerant in the gas-liquid two-phase state and the refrigerant in the gas state flows in the secondary-side second communicating pipe 9. According to the operating state, either one of the refrigerant in the gas-liquid two-phase state and the refrigerant in the liquid state flows in the secondary-side third communicating pipe 7. In addition, according to the kind of the second refrigerant, the refrigerant in the supercritical state is caused to flow in the secondary-side third communicating pipe 7 in correspondence with the operating state.

[0060] The secondary-side refrigerant circuit 10 is configured in a manner that the heat-source circuit 12, the branch circuits 14a, 14b, 14c, and the utilization circuits 13a, 13b, 13c are connected to each other.

[0061] The heat-source circuit 12 mainly has the secondary-side compressor 21 (corresponding to the second compressor), the secondary-side switching mechanism 22, the first heat-source pipe 28, the second heat-source pipe 29, the suction flow path 23, the discharge flow path 24, the third heat-source pipe 25, the fourth heat-source pipe 26, the fifth heat-source pipe 27, the cascade heat exchanger 35, the heat-source-side expansion valve 36 (corresponding to the second expansion valve), the third stop valve 31, the first stop valve 32, the second stop valve 33, the secondary-side accumulator 30, the oil separator 34, the oil return circuit 40, the secondary-side receiver 45, the bypass circuit 46, the bypass expansion valve 46a, the secondary-side subcooling heat exchanger 47, the secondary-side subcooling circuit 48, and the secondary-side subcooling expansion valve 48a.

[0062] The secondary-side compressor 21 is a device for compressing the secondary-side refrigerant, for example, constituted by a scroll type or the like volumetric compressor capable of making the operation capacity variable by inverter control of the compressor motor 21a. In addition, the secondary-side compressor 21 is controlled so that the larger the load, the larger the operation capacity, according to the load at the time of operation.

[0063] The secondary-side switching mechanism 22 is a mechanism capable of switching the connection state of the secondary-side refrigerant circuit 10, particularly the flow path of the refrigerant within the heat source circuit 12. In the present embodiment, the secondary-side switching mechanism 22 is constituted by four switching valves 22a, 22b, 22c, 22d as two-way valves arranged in a ring-shaped flow path. In addition, as an alternative, a structure in which a plurality of three-way switching valves are combined can also be used as the secondary-side switching mechanism 22. The secondary-side switching mechanism 22 has a first switching valve 22a provided in a flow path connecting the discharge flow path 24 and the third heat source pipe 25, a second switching valve 22b provided in a flow path connecting the discharge flow path 24 and the first heat source pipe 28, a third switching valve 22c provided in a flow path connecting the suction flow path 23 and the third heat source pipe 25, and a fourth switching valve 22d provided in a flow path connecting the suction flow path 23 and the first heat source pipe 28. In the present embodiment, the first switching valve 22a, the second switching valve 22b, the third switching valve 22c, and the fourth switching valve 22d are solenoid valves each switched between an open state and a closed state.

[0064] In a case where the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant, the secondary-side switching mechanism 22 is in a first connection state in which the first switching valve 22a is set to an open state to connect the discharge side of the secondary-side compressor 21 and the gas side of the secondary-side flow path 35a of the cascade heat exchanger 35, and the third switching valve 22c is set to a closed state. Further, in a case where the cascade heat exchanger 35 functions as an evaporator of the secondary-side refrigerant, the secondary-side switching mechanism 22 is in a second connection state in which the third switching valve 22c is set to an open state to connect the suction side of the secondary-side compressor 21 and the gas side of the secondary-side flow path 35a of the cascade heat exchanger 35, and the first switching valve 22a is set to a closed state. Further, in a case where the secondary-side refrigerant discharged from the secondary-side compressor 21 is sent to the secondary-side first communication pipe 8, the secondary-side switching mechanism 22 is in a third connection state in which the second switching valve 22b is set to an open state to connect the discharge side of the secondary-side compressor 21 and the secondary-side first communication pipe 8, and the fourth switching valve 22d is set to a closed state. Further, in a case where the refrigerant flowing in the secondary-side first communication pipe 8 is sucked into the secondary-side compressor 21, the secondary-side switching mechanism 22 is in a fourth connection state in which the fourth switching valve 22d is set to an open state to connect the secondary-side first communication pipe 8 and the suction side of the secondary-side compressor 21, and the second switching valve 22b is set to a closed state.

[0065] As described above, the cascade heat exchanger 35 is a device for performing heat exchange between the refrigerant such as R32 as the primary-side refrigerant and the refrigerant such as carbon dioxide as the secondary-side refrigerant without mixing each other. Further, the cascade heat exchanger 35 has the secondary-side flow path 35a through which the secondary-side refrigerant of the secondary-side refrigerant circuit 10 flows and the primary-side flow path 35b through which the primary-side refrigerant of the primary-side refrigerant circuit 5a flows, and thus is shared by the primary-side unit 5 and the heat-source unit 2. Further, in the present embodiment, the cascade heat exchanger 35 is disposed inside the heat-source casing 2x of the heat-source unit 2. The gas side of the primary-side flow path 35b of the cascade heat exchanger 35 passes through the second connection pipe 113 and the second gas shutoff valve 107, and extends to the primary-side second communication pipe 112 outside the heat-source casing 2x. The liquid side of the primary-side flow path 35b of the cascade heat exchanger 35 passes through the primary-side second expansion valve 102, the first connection pipe 115, and the second liquid shutoff valve 106, and extends to the primary-side first communication pipe 111 outside the heat-source casing 2x.

[0066] The heat-source-side expansion valve 36 is an electric expansion valve capable of performing opening degree adjustment of the liquid side of the cascade heat exchanger 35 to perform adjustment of the flow rate of the secondary-side refrigerant flowing in the cascade heat exchanger 35 and the like. The heat-source-side expansion valve 36 is provided to the fourth heat-source pipe 26.

[0067] The third stop valve 31, the first stop valve 32, and the second stop valve 33 are valves provided to connection ports with external devices, pipes (specifically, the communication pipes 7, 8, and 9). Specifically, the third stop valve 31 is connected to the secondary-side third communication pipe 7 drawn from the heat source unit 2. The first stop valve 32 is connected to the secondary-side first communication pipe 8 drawn from the heat source unit 2. The second stop valve 33 is connected to the secondary-side second communication pipe 9 drawn from the heat source unit 2.

[0068] The first heat source pipe 28 is a refrigerant pipe connecting the first stop valve 32 and the secondary-side switching mechanism 22. Specifically, the first heat source pipe 28 connects the first stop valve 32 and a portion between the second switching valve 22b and the fourth switching valve 22d in the secondary-side switching mechanism 22.

[0069] The suction flow path 23 is a flow path connecting the secondary-side switching mechanism 22 and a suction side of the secondary-side compressor 21. Specifically, the suction flow path 23 connects a portion between the third switching valve 22c and the fourth switching valve 22d in the secondary-side switching mechanism 22 and the suction side of the secondary-side compressor 21. The secondary-side accumulator 30 is provided midway in the suction flow path 23.

[0070] The second heat source pipe 29 is a refrigerant pipe connecting the second stop valve 33 and the secondary-side accumulator 30. In the present embodiment, the second heat source pipe 29 is connected to the suction flow path 23 at a connection site in the suction flow path 23, which is a portion between the second switching valve 22b and the fourth switching valve 22d in the secondary-side switching mechanism 22 and a portion between the secondary-side accumulator 30.

[0071] The discharge flow path 24 is a refrigerant pipe connecting a discharge side of the secondary-side compressor 21 and the secondary-side switching mechanism 22. Specifically, the discharge flow path 24 connects the discharge side of the secondary-side compressor 21 and a portion between the first switching valve 22a and the second switching valve 22b in the secondary-side switching mechanism 22.

[0072] The third heat source pipe 25 is a refrigerant pipe connecting the secondary-side switching mechanism 22 and a gas side of the cascade heat exchanger 35. Specifically, the third heat source pipe 25 connects a portion between the first switching valve 22a and the third switching valve 22c in the secondary-side switching mechanism 22 and a gas side end portion of the secondary-side flow path 35a in the cascade heat exchanger 35.

[0073] The fourth heat-source pipe 26 is a refrigerant pipe that connects the liquid side of the cascade heat exchanger 35 (the side opposite the gas side, the side opposite the side provided with the secondary-side switching mechanism 22) and the secondary-side receiver 45. Specifically, the fourth heat-source pipe 26 connects the liquid side end portion (the end portion on the side opposite the gas side) of the secondary-side flow path 35a in the cascade heat exchanger 35 and the secondary-side receiver 45.

[0074] The secondary-side receiver 45 is a refrigerant container that stores the remaining refrigerant in the secondary-side refrigerant circuit 10. The fourth heat-source pipe 26, the fifth heat-source pipe 27, and the bypass circuit 46 extend from the secondary-side receiver 45.

[0075] The bypass circuit 46 is a refrigerant pipe that connects the region above, i.e., the gas phase region, inside the secondary-side receiver 45 and the suction flow path 23. Specifically, the bypass circuit 46 is connected between the secondary-side switching mechanism 22 and the secondary-side accumulator 30 in the suction flow path 23. A bypass expansion valve 46a is provided in the bypass circuit 46. The bypass expansion valve 46a is an electric expansion valve that can adjust the amount of refrigerant guided from inside the secondary-side receiver 45 to the suction side of the secondary-side compressor 21 by adjusting the opening degree.

[0076] The fifth heat-source pipe 27 is a refrigerant pipe that connects the secondary-side receiver 45 and the third stop valve 31.

[0077] The secondary-side subcooling circuit 48 is a refrigerant pipe that connects a portion of the fifth heat-source pipe 27 and the suction flow path 23. Specifically, the secondary-side subcooling circuit 48 is connected between the secondary-side switching mechanism 22 and the secondary-side accumulator 30 in the suction flow path 23. In addition, in the present embodiment, the secondary-side subcooling circuit 48 extends branched from between the secondary-side receiver 45 and the secondary-side subcooling heat exchanger 47.

[0078] The secondary-side subcooling heat exchanger 47 is a heat exchanger that exchanges heat between the refrigerant flowing in the flow path belonging to the fifth heat-source pipe 27 and the refrigerant flowing in the flow path belonging to the secondary-side subcooling circuit 48. In the present embodiment, the secondary-side subcooling heat exchanger 47 is provided between the portion of the fifth heat-source pipe 27 from which the secondary-side subcooling circuit 48 branches and the third stop valve 31. A secondary-side subcooling expansion valve 48a is provided between the portion of the secondary-side subcooling circuit 48 from which the fifth heat-source pipe 27 branches and the secondary-side subcooling heat exchanger 47. The secondary-side subcooling expansion valve 48a is an electric expansion valve that can adjust the opening degree, and supplies the secondary-side subcooling heat exchanger 47 with refrigerant that has been depressurized.

[0079] The secondary-side accumulator 30 is a container that can accumulate the secondary-side refrigerant, and is provided on the suction side of the secondary-side compressor 21.

[0080] An oil separator 34 is provided midway in the discharge flow path 24. The oil separator 34 is a device for separating refrigerant oil accompanying the secondary-side refrigerant discharged from the secondary-side compressor 21 from the secondary-side refrigerant and returning it to the secondary-side compressor 21.

[0081] An oil return circuit 40 is provided to connect the oil separator 34 and the suction flow path 23. The flow path of the oil return circuit 40 extending from the oil separator 34 has an oil return flow path 41 extending in a manner to join the portion between the secondary-side reservoir 30 and the suction side of the secondary-side compressor 21 in the suction flow path 23. Midway in the oil return flow path 41, an oil return capillary tube 42 and an oil return on-off valve 44 are provided. By controlling the oil return on-off valve 44 to be in an open state, the refrigerant oil separated in the oil separator 34 passes through the oil return capillary tube 42 of the oil return flow path 41 and returns to the suction side of the secondary-side compressor 21. Here, in the present embodiment, the oil return on-off valve 44 controls the amount of return of the refrigerant oil passing through the oil return circuit 40 by repeatedly maintaining the open state for a prescribed time and maintaining the closed state for a prescribed time in the case where the secondary-side compressor 21 is in an operating state in the secondary-side refrigerant circuit 10. In addition, the oil return on-off valve 44 is an electromagnetic valve in the present embodiment which is subjected to on-off control, but can also be a motor-operated expansion valve which is configured to be capable of degree adjustment and which omits the oil return capillary tube 42.

[0082] Hereinafter, the utilization circuit 13a will be described. Since the utilization circuits 13b, 13c are the same structure as the utilization circuit 13a, for the utilization circuits 13b, 13c, the symbol "b" or "c" is marked in place of "a" indicating each portion of the utilization circuit 13a, and the description of each portion is omitted.

[0083] The utilization circuit 13a mainly has a utilization-side heat exchanger 52a (corresponding to a second heat exchanger), a first utilization pipe 57a, a second utilization pipe 56a, and a utilization-side expansion valve 51a.

[0084] The utilization-side heat exchanger 52a is a device for performing heat exchange between refrigerant and indoor air, and is constituted by, for example, a finned tube heat exchanger constituted by a plurality of heat transfer tubes and fins. In addition, a plurality of utilization-side heat exchangers 52a, 52b, 52c are connected in parallel with respect to the secondary-side switching mechanism 22, the suction flow path 23, and the cascade heat exchanger 35.

[0085] One end of the second utilization pipe 56a is connected to the liquid side (the side opposite to the gas side) of the utilization-side heat exchanger 52a of the first utilization unit 3a. The other end of the second utilization pipe 56a is connected to the second branch connection pipe 16a. The utilization-side expansion valve 51a described above is provided midway in the second utilization pipe 56a.

[0086] The utilization-side expansion valve 51a is an electric expansion valve capable of opening degree adjustment, and adjusts the flow rate of the refrigerant flowing in the utilization-side heat exchanger 52a, and the like. The utilization-side expansion valve 51a is provided to the second utilization pipe 56a.

[0087] One end of the first utilization pipe 57a is connected to the gas side of the utilization-side heat exchanger 52a of the first utilization unit 3a. In the present embodiment, the first utilization pipe 57a is connected to the side of the utilization-side heat exchanger 52a opposite the utilization-side expansion valve 51a. The other end of the first utilization pipe 57a is connected to the first branch connection pipe 15a.

[0088] Hereinafter, the branch circuits 14a, 14b, 14c will be described, and since the branch circuits 14b, 14c are the same structure as the branch circuit 14a, for the branch circuits 14b, 14c, "b" or "c" is added instead of the symbol "a" indicating each part of the branch circuit 14a, and the description of each part is omitted.

[0089] The branch circuit 14a mainly has a merging pipe 62a, a first branch pipe 63a, a second branch pipe 64a, a first adjustment valve 66a, a second adjustment valve 67a, and a third branch pipe 61a.

[0090] One end of the merging pipe 62a is connected to the first branch connection pipe 15a. The first branch pipe 63a and the second branch pipe 64a are connected to the other end of the merging pipe 62a in a branched manner.

[0091] The side of the first branch pipe 63a opposite the merging pipe 62a is connected to the secondary-side first communication pipe 8. The first branch pipe 63a is provided with the first adjustment valve 66a capable of opening and closing. Here, as the first adjustment valve 66a, an electric expansion valve capable of opening degree adjustment is used, but a solenoid valve or the like capable of only opening and closing can also be used.

[0092] The side of the second branch pipe 64a opposite the merging pipe 62a is connected to the secondary-side second communication pipe 9. The second branch pipe 64a is provided with the second adjustment valve 67a capable of opening and closing. Here, as the second adjustment valve 67a, an electric expansion valve capable of opening degree adjustment is used, but a solenoid valve or the like capable of only opening and closing can also be used.

[0093] One end of the third branch pipe 61a is connected to the second branch connection pipe 16a. The other end of the third branch pipe 61a is connected to the secondary-side third communication pipe 7.

[0094] Further, the first branch unit 6a functions as follows when the refrigeration operation described below is performed by setting the first adjustment valve 66a to the open state and the second adjustment valve 67a to the closed state. The first branch unit 6a sends the refrigerant flowing through the second side third communication pipe 7 and flowing into the third branch pipe 61a to the second branch connection pipe 16a. Further, the refrigerant flowing through the second branch connection pipe 16a and flowing in the second use pipe 56a of the first use unit 3a is sent to the use side heat exchanger 52a of the first use unit 3a through the use side expansion valve 51a. Then, the refrigerant sent to the use side heat exchanger 52a is evaporated by heat exchange with indoor air, and flows in the first branch connection pipe 15a through the first use pipe 57a. The refrigerant flowing in the first branch connection pipe 15a is sent to the confluence pipe 62a of the first branch unit 6a. The refrigerant flowing in the confluence pipe 62a is branched and flows to the first branch pipe 63a and the second branch pipe 64a. The refrigerant flowing in the first branch pipe 63a through the first adjustment valve 66a is sent to the second side first communication pipe 8. The refrigerant flowing in the second branch pipe 64a through the second adjustment valve 67a is sent to the second side second communication pipe 9.

[0095] Further, the first branch unit 6a functions as follows when the refrigeration operation described below is performed by setting the first adjustment valve 66a to the open state and the second adjustment valve 67a to the closed state. The first branch unit 6a sends the refrigerant flowing through the second side third communication pipe 7 and flowing into the third branch pipe 61a to the second branch connection pipe 16a. Further, the refrigerant flowing through the second branch connection pipe 16a and flowing in the second use pipe 56a of the first use unit 3a is sent to the use side heat exchanger 52a of the first use unit 3a through the use side expansion valve 51a. Then, the refrigerant sent to the use side heat exchanger 52a is evaporated by heat exchange with indoor air, and flows in the first branch connection pipe 15a through the first use pipe 57a. The refrigerant flowing in the first branch connection pipe 15a is sent to the confluence pipe 62a of the first branch unit 6a. The refrigerant flowing in the confluence pipe 62a is branched and flows to the first branch pipe 63a and the second branch pipe 64a. The refrigerant flowing in the first branch pipe 63a through the first adjustment valve 66a is sent to the second side first communication pipe 8. The refrigerant flowing in the second branch pipe 64a through the second adjustment valve 67a is sent to the second side second communication pipe 9.

[0096] Further, the first branch unit 6a, when performing the following cooling operation, functions as follows by setting the second regulating valve 67a to the open state or the closed state and setting the first regulating valve 66a to the open state according to the operation state as described below. In the first branch unit 6a, the refrigerant flowing through the second branch pipe 63b via the second branch connection pipe 16b flows in the third branch pipe 61a of the first branch unit 6a, and is then sent to the second side third communication pipe 7 via the second regulating valve 67a.

[0097] Further, the first branch unit 6a, when performing the following cooling operation, functions as follows by setting the second regulating valve 67a to the open state or the closed state and setting the first regulating valve 66a to the open state according to the operation state as described below. In the first branch unit 6a, the refrigerant flowing through the second branch pipe 63b via the second branch connection pipe 16b flows in the third branch pipe 61a of the first branch unit 6a, and is then sent to the second side third communication pipe 7 via the second regulating valve 67a.

[0098] Not only the first branch unit 6a has the above-described function, but also the second branch unit 6b and the third branch unit 6c have the above-described function. Therefore, the first branch unit 6a, the second branch unit 6b, and the third branch unit 6c can individually switch whether each of the utilization side heat exchangers 52a, 52b, and 52c functions as an evaporator or a radiator for the refrigerant.

[0099] (4) Primary side unit

[0100] The primary side unit 5 is provided in a space different from a space in which the utilization units 3a, 3b, and 3c and the branch units 6a, 6b, and 6c are arranged, such as a ceiling.

[0101] The primary-side unit 5 is configured to have, in a not-shown primary-side housing, a part of the above-described primary-side refrigerant circuit 5a, a primary-side fan 75, various sensors, and a primary-side control section 70 (corresponding to the first control section).

[0102] The primary-side unit 5 has a primary-side compressor 71, a primary-side switching mechanism 72, a primary-side heat exchanger 74, a primary-side first expansion valve 76, a primary-side subcooling heat exchanger 103, a primary-side subcooling circuit 104, a primary-side subcooling expansion valve 104a, a first liquid shut-off valve 108, a first gas shut-off valve 109, and a primary-side accumulator 105 as a part of the primary-side refrigerant circuit 5a.

[0103] The primary-side fan 75 is provided in the primary-side unit 5 to generate an air flow that guides outdoor air to the primary-side heat exchanger 74 and discharges the air to the outside after heat-exchanging with the primary-side refrigerant flowing in the primary-side heat exchanger 74. The primary-side fan 75 is driven by a primary-side fan motor 75a.

[0104] Further, various sensors are provided in the primary-side unit 5. Specifically, an outdoor air temperature sensor 77 that detects the temperature of outdoor air before passing through the primary-side heat exchanger 74, a primary-side discharge pressure sensor 78 that detects the pressure of the primary-side refrigerant discharged from the primary-side compressor 71, a primary-side suction pressure sensor 79 that detects the pressure of the primary-side refrigerant sucked into the primary-side compressor 71, a primary-side suction temperature sensor 81 that detects the temperature of the primary-side refrigerant sucked into the primary-side compressor 71, and a primary-side heat-exchange temperature sensor 82 that detects the temperature of the refrigerant flowing in the primary-side heat exchanger 74 are provided.

[0105] The primary-side control section 70 controls the operation of each of the parts 71 (71a), 72, 75 (75a), 76, 104a provided in the primary-side unit 5. Also, the primary-side control section 70 has a CPU, a microcomputer, or the like as a processor and a memory provided for the control of the primary-side unit 5, and is configured to be able to exchange control signals and the like with a remote controller (not shown) and exchange control signals and the like with the heat-source-side control section 20 of the secondary-side unit 4, the branch unit control sections 60a, 60b, 60c, and the utilization-side control sections 50a, 50b, 50c.

[0106] (5) Heat-source unit

[0107] The heat-source unit 2 is provided in a space different from the space in which the utilization units 3a, 3b, 3c and the branch units 6a, 6b, 6c are arranged, such as a roof.

[0108] The heat source unit 2 is connected to the branch units 6a, 6b, 6c via the communicating pipes 7, 8, 9, and constitutes a part of the secondary-side refrigerant circuit 10. Further, the heat source unit 2 is connected to the primary-side unit 5 via the primary-side first communicating pipe 111 and the primary-side second communicating pipe 112, and constitutes a part of the primary-side refrigerant circuit 5a.

[0109] The heat source unit 2 is constituted mainly of the above-described heat source circuit 12, various sensors, a heat source-side control portion 20 (corresponding to the second control portion), a second liquid shut-off valve 106 constituting a part of the primary-side refrigerant circuit 5a, a first connection pipe 115, a primary-side second expansion valve 102, a second connection pipe 113, and a second gas shut-off valve 107, in a heat source housing not shown.

[0110] The heat source unit 2 is provided with a secondary-side suction pressure sensor 37 that detects the pressure of the secondary-side refrigerant on the suction side of the secondary-side compressor 21, a secondary-side discharge pressure sensor 38 that detects the pressure of the secondary-side refrigerant on the discharge side of the secondary-side compressor 21, a secondary-side discharge temperature sensor 39 that detects the temperature of the secondary-side refrigerant on the discharge side of the secondary-side compressor 21, a secondary-side suction temperature sensor 88 that detects the temperature of the secondary-side refrigerant on the suction side of the secondary-side compressor 21, a secondary-side first temperature sensor 83 that detects the temperature of the secondary-side refrigerant flowing between the secondary-side flow path 35a of the cascade heat exchanger 35 and the heat source-side expansion valve 36, a primary-side first temperature sensor 121 that detects the temperature of the primary-side refrigerant flowing between the primary-side flow path 35b of the cascade heat exchanger 35 and the primary-side second expansion valve 102, a primary-side second temperature sensor 122 that detects the temperature of the primary-side refrigerant flowing in the second connection pipe 113 between the primary-side flow path 35b of the cascade heat exchanger 35 and the second gas shut-off valve 107, a receiver outlet temperature sensor 84 that detects the temperature of the secondary-side refrigerant flowing between the secondary-side receiver 45 and the secondary-side subcooling heat exchanger 47, a bypass circuit temperature sensor 85 that detects the temperature of the secondary-side refrigerant flowing on the downstream side of the bypass expansion valve 46a in the bypass circuit 46, a subcooling outlet temperature sensor 86 that detects the temperature of the secondary-side refrigerant flowing between the secondary-side subcooling heat exchanger 47 and the third shut-off valve 31, and a subcooling circuit temperature sensor 87 that detects the temperature of the secondary-side refrigerant flowing on the outlet side of the secondary-side subcooling heat exchanger 47 in the secondary-side subcooling circuit 48.

[0111] The heat-source-side control unit 20 controls the operation of each portion 21 (21a), 22, 36, 44, 46a, 48a, 102 provided in the heat-source unit 2. In addition, the heat-source-side control unit 20 controls the valve opening degree of the first-stage second expansion valve 102 which is a component that constitutes a part of the primary-side refrigerant circuit 5a, not the secondary-side refrigerant circuit 10. The heat-source-side control unit 20 has a CPU, a microcomputer, or the like as a processor and a memory provided for the purpose of controlling the heat-source unit 2, and is configured to be able to exchange control signals and the like with the primary-side control unit 70 of the primary-side unit 5, the utilization-side control units 50a, 50b, 50c of the utilization units 3a, 3b, 3c, and the branch unit control units 60a, 60b, 60c.

[0112] (6) Utilization Unit

[0113] The utilization units 3a, 3b, 3c are provided by being embedded in, suspended from, or wall-mounted to a ceiling or a wall surface of an indoor space of a building or the like.

[0114] The utilization units 3a, 3b, 3c are connected to the heat-source unit 2 via the communication pipes 7, 8, 9.

[0115] The utilization units 3a, 3b, 3c have utilization circuits 13a, 13b, 13c that constitute a part of the secondary-side refrigerant circuit 10.

[0116] Hereinafter, the structure of the utilization-side units 3a, 3b, 3c will be described. Since the second utilization unit 3b and the third utilization unit 3c have the same structure as the first utilization unit 3a, here, only the structure of the first utilization unit 3a will be described, and for the structures of the second utilization unit 3b and the third utilization unit 3c, the symbol "b" or "c" is added in place of "a" that indicates each portion of the first utilization unit 3a, and the description of each portion is omitted.

[0117] The first utilization unit 3a mainly has the above-described utilization circuit 13a, an indoor fan 53a, a utilization-side control unit 50a, and various sensors. In addition, the indoor fan 53a has an indoor fan motor 54a.

[0118] The indoor fan 53a generates an air flow that sucks indoor air into the unit, exchanges heat with the refrigerant flowing in the utilization-side heat exchanger 52a, and then supplies the air as supply air to the indoor space. The indoor fan 53a is driven by the indoor fan motor 54a.

[0119] The utilization unit 3a is provided with a liquid-side temperature sensor 58a that detects the temperature of the refrigerant on the liquid side of the utilization-side heat exchanger 52a. Further, the utilization unit 3a is provided with an indoor temperature sensor 55a that detects the indoor temperature, which is the temperature of the air introduced from the room before passing through the utilization-side heat exchanger 52a. Further, the utilization unit 3a is provided with an indoor blow-out temperature sensor 59a that detects the temperature of the air that has passed through the utilization-side heat exchanger 52a.

[0120] The utilization-side control section 50a controls the operation of each of the parts 51a, 53a (54a) that constitute the utilization unit 3a. Further, the utilization-side control section 50a has a CPU, a microcomputer, or the like as a processor and a memory provided for the control of the utilization unit 3a, and is configured to be able to exchange control signals and the like with a remote controller (not shown) and exchange control signals and the like with the heat-source-side control section 20 of the secondary-side unit 4, the branch unit control sections 60a, 60b, 60c, and the primary-side control section 70 of the primary-side unit 5.

[0121] Further, the second utilization unit 3b has a utilization circuit 13b, an indoor fan 53b, a utilization-side control section 50b, and an indoor fan motor 54b. The third utilization unit 3c has a utilization circuit 13c, an indoor fan 53c, a utilization-side control section 50c, and an indoor fan motor 54c.

[0122] (7) Branch Unit

[0123] The branch units 6a, 6b, 6c are provided in a space or the like on the back side of the ceiling of the indoor space of a building or the like.

[0124] The branch units 6a, 6b, 6c correspond to the utilization units 3a, 3b, 3c one to one and are connected. The branch units 6a, 6b, 6c are connected to the heat-source unit 2 via the communication pipes 7, 8, 9.

[0125] Next, the structure of the branch units 6a, 6b, 6c will be described. Further, since the second branch unit 6b and the third branch unit 6c are of the same structure as the first branch unit 6a, here, only the structure of the first branch unit 6a will be described, and for the structures of the second branch unit 6b and the third branch unit 6c, the symbol "b" or "c" is respectively indicated in place of "a" that indicates each part of the first branch unit 6a, and the description of each part is omitted.

[0126] The first branch unit 6a mainly has the above-described branch circuit 14a and a branch unit control section 60a.

[0127] The branch unit control section 60a controls the operation of each part 66a, 67a that constitutes the branch unit 6a. Also, the branch unit control section 60a has a CPU, a microcomputer, or the like, and a memory that are provided for the control of the branch unit 6a, and is configured to be able to exchange control signals and the like with a remote controller (not shown) and to exchange control signals and the like with the heat source side control section 20 of the secondary side unit 4, the utilization units 3a, 3b, 3c, and the primary side control section 70 of the primary side unit 5.

[0128] Also, the second branch unit 6b has a branch circuit 14b and a branch unit control section 60b. The third branch unit 6c has a branch circuit 14c and a branch unit control section 60c.

[0129] (8) Control Section

[0130] In the refrigeration cycle system 1, the above-described heat source side control section 20, the utilization side control sections 50a, 50b, 50c, the branch unit control sections 60a, 60b, 60c, and the primary side control section 70 are communicably connected to each other via a wire or wirelessly, thereby constituting a control section 80. Therefore, the above-described control section 80 controls the operation of each part 21 (21a), 22, 36, 44, 46a, 48a, 51a, 51b, 51c, 53a, 53b, 53c (54a, 54b, 54c), 66a, 66b, 66c, 67a, 67b, 67c, 71 (71a), 72, 75 (75a), 76, 102, 104a on the basis of detection information of various sensors 37, 38, 39, 83, 84, 85, 86, 87, 88, 77, 78, 79, 81, 82, 58a, 58b, 58c, 59a, 59b, 59c, 121, 122, and the like, and instruction information and the like received from a remote controller and the like that are not shown.

[0131] (9) Operation of Refrigeration Cycle System

[0132] Next, the operation of the refrigeration cycle system 1 will be described. Figures 3 to 6 The operation of the refrigeration cycle system 1 will be described.

[0133] The refrigeration cycle operation of the refrigeration cycle system 1 can be mainly divided into a refrigeration operation, a heating operation, a refrigeration main operation, and a heating main operation.

[0134] Here, the refrigeration operation is a refrigeration cycle operation in which only the utilization units that perform an operation in which the utilization side heat exchanger functions as an evaporator of refrigerant exist, and the cascade heat exchanger 35 functions as a radiator of secondary side refrigerant with respect to the evaporation load of the entire utilization units.

[0135] The heating operation is a refrigeration cycle operation in which only the utilization unit in which the utilization-side heat exchanger functions as a radiator of the refrigerant is present, and the cascade heat exchanger 35 functions as an evaporator of the secondary-side refrigerant with respect to the heat release load of the entire utilization unit.

[0136] The refrigeration main operation is an operation in which the utilization unit in which the utilization-side heat exchanger functions as an evaporator of the refrigerant and the utilization unit in which the utilization-side heat exchanger functions as a radiator of the refrigerant are mixed. The refrigeration main operation is a refrigeration cycle operation in which the evaporation load is predominant in the heat load of the entire utilization unit, and the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant with respect to the evaporation load of the entire utilization unit.

[0137] The heating main operation is an operation in which the utilization unit in which the utilization-side heat exchanger functions as an evaporator of the refrigerant and the utilization unit in which the utilization-side heat exchanger functions as a radiator of the refrigerant are mixed. The heating main operation is a refrigeration cycle operation in which the heat release load is predominant in the heat load of the entire utilization unit, and the cascade heat exchanger 35 functions as an evaporator of the secondary-side refrigerant with respect to the heat release load of the entire utilization unit.

[0138] In addition, the operation of the refrigeration cycle system 1 including the above-described refrigeration cycle operation is performed by the above-described control section 80.

[0139] (9-1) Refrigeration operation

[0140] In the refrigeration operation, for example, the utilization-side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as evaporators of the refrigerant, and the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant. In this refrigeration operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1 are configured as shown in FIG. 9. Figure 3 Figure 3 The arrows indicated in the primary-side refrigerant circuit 5a and the arrows indicated in the secondary-side refrigerant circuit 10 indicate the flow of the refrigerant at the time of the refrigeration operation.

[0141] Specifically, in the primary-side unit 5, the cascade heat exchanger 35 functions as an evaporator of the primary-side refrigerant by switching the primary-side switching mechanism 72 to the fifth connection state. In addition, the fifth connection state of the primary-side switching mechanism 72 is a state in which the first connection port 72a and the third connection port 72c are connected to each other, and the second connection port 72b and the fourth connection port 72d are connected to each other. Figure 3 ​the first liquid stop valve 108, a part of the refrigerant passes through the first cooling heat exchanger 103 and flows toward the first liquid stop valve 108, and the other part of the refrigerant branches and flows to the first subcooling circuit 104. The refrigerant flowing in the first subcooling circuit 104 is depressurized when passing through the first subcooling expansion valve 104a. The refrigerant flowing from the first liquid stop valve 108 toward the first subcooling heat exchanger 103 exchanges heat with the refrigerant depressurized by the first subcooling expansion valve 104a and flowing in the first subcooling circuit 104 in the first subcooling heat exchanger 103, and is cooled to a subcooled state. The refrigerant in the subcooled state flows in the order of the first communication pipe 111, the second liquid stop valve 106, and the first connection pipe 115, is depressurized in the second expansion valve 102. The refrigerant depressurized in the second expansion valve 102 is evaporated while flowing in the first side flow path 35b of the cascade heat exchanger 35 by exchanging heat with the second side refrigerant flowing in the second side flow path 35a, passes through the second connection pipe 113, and flows toward the second gas stop valve 107. The refrigerant passing through the second gas stop valve 107 reaches the first switching mechanism 72 after passing through the second communication pipe 112 and the first gas stop valve 109. The refrigerant passing through the first switching mechanism 72 merges with the refrigerant flowing in the first subcooling circuit 104 in the first suction flow path 125a, and is then sucked into the first compressor 71 via the first accumulator 105 and the second suction flow path 125b.

[0142] Further, in the heat source unit 2, the cascade heat exchanger 35 is made to function as a radiator of the secondary-side refrigerant by switching the secondary-side switching mechanism 22 to the first connection state and the fourth connection state. In addition, the first connection state of the secondary-side switching mechanism 22 is a connection state in which the first switching valve 22a is in an open state and the third switching valve 22c is in a closed state. The fourth connection state of the secondary-side switching mechanism 22 is a connection state in which the fourth switching valve 22d is in an open state and the second switching valve 22b is in a closed state. Here, the opening degree of the heat source-side expansion valve 36 is adjusted. In the first to third utilization units 3a, 3b, 3c, the first adjustment valves 66a, 66b, 66c and the second adjustment valves 67a, 67b, 67c are controlled to be in an open state. Thus, the utilization-side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as evaporators of the refrigerant. Further, the utilization-side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c and the suction side of the secondary-side compressor 21 of the heat source unit 2 all become connected via the first utilization pipe 57a, 57b, 57c, the first branch connection pipe 15a, 15b, 15c, the merging pipe 62a, 62b, 62c, the first branch pipe 63a, 63b, 63c, the second branch pipe 64a, 64b, 64c, the secondary-side first communication pipe 8, and the secondary-side second communication pipe 9. Further, the secondary-side supercooling expansion valve 48a is controlled in the opening degree in such a manner that the degree of supercooling of the secondary-side refrigerant flowing from the outlet of the secondary-side supercooling heat exchanger 47 toward the secondary-side third communication pipe 7 becomes a prescribed value. The bypass expansion valve 46a is controlled to be in a closed state. In the utilization units 3a, 3b, 3c, the utilization-side expansion valves 51a, 51b, 51c are adjusted in the opening degree.

[0143] In the above-described secondary-side refrigerant circuit 10, the secondary-side high-pressure refrigerant compressed and discharged by the secondary-side compressor 21 passes through the secondary-side switching mechanism 22 and is delivered to the secondary-side flow path 35a of the cascade heat exchanger 35. In the cascade heat exchanger 35, the secondary-side high-pressure refrigerant flowing in the secondary-side flow path 35a is radiated, and the primary-side refrigerant flowing in the primary-side flow path 35b of the cascade heat exchanger 35 is evaporated. The secondary-side refrigerant radiated in the cascade heat exchanger 35 flows into the secondary-side receiver 45 after passing through the heat source-side expansion valve 36 adjusted in the opening degree. A part of the refrigerant flowing out of the secondary-side receiver 45 bifurcates toward the secondary-side supercooling circuit 48, is depressurized in the secondary-side supercooling expansion valve 48a, and merges with the secondary-side suction flow path 23. In the secondary-side supercooling heat exchanger 47, the other part of the refrigerant flowing out of the secondary-side receiver 45 is cooled by the refrigerant flowing in the secondary-side supercooling circuit 48, passes through the third stop valve 31, and is delivered to the secondary-side third communication pipe 7.

[0144] Next, the refrigerant delivered to the third communicating pipe 7 on the secondary side is branched into three and flows through the third branch pipes 61a, 61b, 61c of the first to third branch units 6a, 6b, 6c. Then, the refrigerant flowing in the second branch connection pipes 16a, 16b, 16c is delivered to the second use pipes 56a, 56b, 56c of the first to third use units 3a, 3b, 3c. The refrigerant delivered to the second use pipes 56a, 56b, 56c is delivered to the use-side expansion valves 51a, 51b, 51c of the use units 3a, 3b, 3c.

[0145] Next, the refrigerant that has passed through the use-side expansion valves 51a, 51b, 51c whose openings have been adjusted exchanges heat with indoor air supplied by the indoor fans 53a, 53b, 53c in the use-side heat exchangers 52a, 52b, 52c. Thus, the refrigerant flowing in the use-side heat exchangers 52a, 52b, 52c evaporates and becomes low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. Thus, the room is cooled. The low-pressure gas refrigerant evaporated in the use-side heat exchangers 52a, 52b, 52c flows through the first use pipes 57a, 57b, 57c, and through the first branch connection pipes 15a, 15b, 15c, and is delivered to the merging pipes 62a, 62b, 62c of the first to third branch units 6a, 6b, 6c.

[0146] Then, the low-pressure gas refrigerant delivered to the merging pipes 62a, 62b, 62c is branched and flows toward the first branch pipes 63a, 63b, 63c and the second branch pipes 64a, 64b, 64c. The refrigerant that has passed through the first regulating valves 66a, 66b, 66c in the first branch pipes 63a, 63b, 63c is delivered to the first communicating pipe 8 on the secondary side. The refrigerant that has passed through the second regulating valves 67a, 67b, 67c in the second branch pipes 64a, 64b, 64c is delivered to the second communicating pipe 9 on the secondary side.

[0147] Next, the low-pressure gas refrigerant delivered to the first communicating pipe 8 on the secondary side and the second communicating pipe 9 on the secondary side passes through the first stop valve 32, the second stop valve 33, the first heat source pipe 28, the second heat source pipe 29, the secondary-side switching mechanism 22, the secondary-side suction flow path 23, and the secondary-side accumulator 30, and returns to the suction side of the secondary-side compressor 21.

[0148] Thus, the operation in the cooling operation is performed.

[0149] (9-2) Heating Operation

[0150] During heating operation, for example, the utilization-side heat exchangers 52a, 52b, and 52c of utilization units 3a, 3b, and 3c all function as radiators for the refrigerant. Furthermore, during heating operation, the cascaded heat exchanger 35 functions as an evaporator for the secondary refrigerant. During heating operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1... Figure 4 The structure shown is as described. Figure 4 The arrows marked in the primary refrigerant circuit 5a and the secondary refrigerant circuit 10 indicate the flow of refrigerant during heating operation.

[0151] Specifically, in primary-side unit 5, by switching primary-side switching mechanism 72 to the sixth connection state, the cascaded heat exchanger 35 functions as a radiator for the primary-side refrigerant. The sixth connection state of primary-side switching mechanism 72 is... Figure 4 The connection state is shown by the dashed line in the primary-side switching mechanism 72. Thus, in the primary-side unit 5, the primary-side refrigerant discharged from the primary-side compressor 71, passing through the primary-side switching mechanism 72 and the first gas shut-off valve 109, is delivered to the primary-side flow path 35b of the cascaded heat exchanger 35 via the primary-side second connecting pipe 112 and the second gas shut-off valve 107. The refrigerant flowing in the primary-side flow path 35b of the cascaded heat exchanger 35 condenses by exchanging heat with the secondary-side refrigerant flowing in the secondary-side flow path 35a. The primary-side refrigerant condensed in the cascaded heat exchanger 35 flows in the following sequence: first connecting pipe 115, primary-side second expansion valve 102 (controlled to be fully open), second liquid shut-off valve 106, primary-side first connecting pipe 111, first liquid shut-off valve 108, and primary-side subcooling heat exchanger 103, and is depressurized in the primary-side first expansion valve 76. Furthermore, during heating operation, the primary-side subcooling expansion valve 104a is kept closed, thus preventing refrigerant from flowing in the primary-side subcooling circuit 104, and consequently, heat exchange in the primary-side subcooling heat exchanger 103 does not occur. Additionally, the opening of the primary-side first expansion valve 76 is controlled, for example, to ensure that the superheat of the refrigerant drawn into the primary-side compressor 71 is at a predetermined value. The refrigerant, depressurized in the primary-side first expansion valve 76, evaporates by exchanging heat with outside air supplied from the primary-side fan 75 in the primary-side heat exchanger 74, passes through the primary-side switching mechanism 72 and the primary-side storage tank 105, and is drawn into the primary-side compressor 71.

[0152] Further, in the heat source unit 2, the secondary side switching mechanism 22 is switched to the second connection state and the third connection state. Thereby, the cascade heat exchanger 35 functions as an evaporator of the secondary side refrigerant. The second connection state of the secondary side switching mechanism 22 is a connection state in which the first switching valve 22a is in the closed state and the third switching valve 22c is in the open state. The third connection state of the secondary side switching mechanism 22 is a connection state in which the second switching valve 22b is in the open state and the fourth switching valve 22d is in the closed state. Further, the heat source side expansion valve 36 is adjusted in the opening degree. In the first to third branch units 6a, 6b, 6c, the first adjustment valves 66a, 66b, 66c are controlled to be in the open state, and the second adjustment valves 67a, 67b, 67c are controlled to be in the closed state. Thereby, the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c all function as radiators of the refrigerant. Also, the utilization side heat exchangers 52a, 52b, 52c of the utilization units 3a, 3b, 3c and the discharge side of the secondary side compressor 21 of the heat source unit 2 become a state connected via the discharge flow passage 24, the first heat source pipe 28, the secondary side first communication pipe 8, the first branch pipes 63a, 63b, 63c, the merging pipes 62a, 62b, 62c, the first branch connection pipes 15a, 15b, 15c, and the first utilization pipes 57a, 57b, 57c. Further, the secondary side subcooling expansion valve 48a and the bypass expansion valve 46a are controlled to be in the closed state. In the utilization units 3a, 3b, 3c, the utilization side expansion valves 51a, 51b, 51c are adjusted in the opening degree.

[0153] In the above-described secondary side refrigerant circuit 10, the high-pressure refrigerant compressed and discharged by the secondary side compressor 21 passes through the second switching valve 22b controlled to be in the open state in the secondary side switching mechanism 22, and is delivered to the first heat source pipe 28. The refrigerant delivered to the first heat source pipe 28 passes through the first stop valve 32, and is delivered to the secondary side first communication pipe 8.

[0154] Then, the high-pressure refrigerant delivered to the secondary side first communication pipe 8 is branched into three, and is delivered to the first branch pipes 63a, 63b, 63c of the respective utilization units 3a, 3b, 3c which are the utilization units in operation. The high-pressure refrigerant delivered to the first branch pipes 63a, 63b, 63c passes through the first adjustment valves 66a, 66b, 66c, and flows in the merging pipes 62a, 62b, 62c. Then, the refrigerant flowing through the first branch connection pipes 15a, 15b, 15c and the first utilization pipes 57a, 57b, 57c is delivered to the utilization side heat exchangers 52a, 52b, 52c.

[0155] Next, the high-pressure refrigerant delivered to the utilization-side heat exchangers 52a, 52b, 52c exchanges heat with the indoor air supplied by the indoor fans 53a, 53b, 53c in the utilization-side heat exchangers 52a, 52b, 52c. Thus, the refrigerant flowing in the utilization-side heat exchangers 52a, 52b, 52c is radiated. The indoor air is heated and supplied to the indoor. Thus, the indoor space is heated. The refrigerant radiated in the utilization-side heat exchangers 52a, 52b, 52c flows in the second utilization pipes 56a, 56b, 56c and passes through the utilization-side expansion valves 51a, 51b, 51c which are adjusted in opening degree. Then, the refrigerant flowing through the second branch connection pipes 16a, 16b, 16c flows in the third branch pipes 61a, 61b, 61c of the respective branch units 6a, 6b, 6c.

[0156] Next, the refrigerant delivered to the third branch pipes 61a, 61b, 61c is delivered to the secondary-side third communication pipe 7 and merged.

[0157] Next, the refrigerant delivered to the secondary-side third communication pipe 7 passes through the third stop valve 31 and is delivered to the heat-source-side expansion valve 36. The refrigerant delivered to the heat-source-side expansion valve 36 is adjusted in flow rate in the heat-source-side expansion valve 36 and then delivered to the cascade heat exchanger 35. In the cascade heat exchanger 35, the secondary-side refrigerant flowing in the secondary-side flow path 35a is evaporated to become low-pressure gas refrigerant and is delivered to the secondary-side switching mechanism 22, and the primary-side refrigerant flowing in the primary-side flow path 35b of the cascade heat exchanger 35 is condensed. Next, the secondary-side low-pressure refrigerant delivered to the secondary-side switching mechanism 22 returns to the suction side of the secondary-side compressor 21 through the secondary-side suction flow path 23 and the secondary-side accumulator 30.

[0158] Thus, the operation in the heating operation is performed.

[0159] (9-3) Refrigeration Main Operation

[0160] In the refrigeration main operation, for example, the utilization-side heat exchanger 52a, 52b of the utilization unit 3a, 3b functions as an evaporator of the refrigerant, and the utilization-side heat exchanger 52c of the utilization unit 3c functions as a radiator of the refrigerant. In the refrigeration main operation, the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant. In the refrigeration main operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1 are configured as shown in FIG. 9. Figure 5 The arrows indicated in the primary-side refrigerant circuit 5a and the arrows indicated in the secondary-side refrigerant circuit 10 of FIG. 9 indicate the flow of the refrigerant in the refrigeration main operation. Figure 5

[0161] ​Specifically, in the primary-side unit 5, by switching the primary-side switching mechanism 72 to the fifth connection state (the state shown by the solid line of the primary-side switching mechanism 72), Figure 5 thereby, in the primary-side unit 5, the primary-side refrigerant discharged from the primary-side compressor 71 passes through the primary-side switching mechanism 72 and exchanges heat with the outside air supplied from the primary-side fan 75 in the primary-side heat exchanger 74, thereby being condensed. The primary-side refrigerant condensed in the primary-side heat exchanger 74 passes through the primary-side first expansion valve 76 controlled to be in the fully open state, and a part of the refrigerant passes through the primary-side subcooling heat exchanger 103 and flows toward the first liquid shut-off valve 108, and the other part of the refrigerant branches and flows to the primary-side subcooling circuit 104. The refrigerant flowing in the primary-side subcooling circuit 104 is depressurized when passing through the primary-side subcooling expansion valve 104a. The refrigerant flowing from the primary-side first expansion valve 76 toward the first liquid shut-off valve 108 exchanges heat with the refrigerant depressurized by the primary-side subcooling expansion valve 104a and flowing in the primary-side subcooling circuit 104 in the primary-side subcooling heat exchanger 103, and is cooled to a subcooled state. The refrigerant becoming the subcooled state flows in the order of the primary-side first communication pipe 111, the second liquid shut-off valve 106, and the first connection pipe 115, and is depressurized in the primary-side second expansion valve 102. The refrigerant depressurized in the primary-side second expansion valve 102 exchanges heat with the secondary-side refrigerant flowing in the secondary-side flow path 35a when flowing in the primary-side flow path 35b of the cascade heat exchanger 35, thereby being evaporated, passes through the second connection pipe 113, and flows toward the second gas shut-off valve 107. The refrigerant passing through the second gas shut-off valve 107, after passing through the primary-side second communication pipe 112 and the first gas shut-off valve 109, reaches the primary-side switching mechanism 72. The refrigerant passing through the primary-side switching mechanism 72 merges with the refrigerant flowing through the primary-side subcooling circuit 104 in the first suction flow path 125a, and is then sucked into the primary-side compressor 71 via the primary-side accumulator 105 and the second suction flow path 125b.

[0162] Further, in the heat source unit 2, the secondary-side switching mechanism 22 is switched to the first connection state (the first switching valve 22a is in the open state and the third switching valve 22c is in the closed state) and the third connection state (the second switching valve 22b is in the open state and the fourth switching valve 22d is in the closed state), whereby the cascade heat exchanger 35 functions as a radiator of the secondary-side refrigerant. Further, the heat source-side expansion valve 36 is subjected to opening degree adjustment. In the first to third branch units 6a, 6b, 6c, the first adjustment valves 66c and the second adjustment valves 67a, 67b are controlled to the open state, and the first adjustment valves 66a, 66b and the second adjustment valve 67c are controlled to the closed state. Thereby, the utilization-side heat exchangers 52a, 52b of the utilization units 3a, 3b function as evaporators of the refrigerant, and the utilization-side heat exchanger 52c of the utilization unit 3c functions as a radiator of the refrigerant. Further, the utilization-side heat exchangers 52a, 52b of the utilization units 3a, 3b and the suction side of the secondary-side compressor 21 of the heat source unit 2 become a state connected via the secondary-side second communication pipe 9, and the utilization-side heat exchanger 52c of the utilization unit 3c and the discharge side of the secondary-side compressor 21 of the heat source unit 2 become a state connected via the secondary-side first communication pipe 8. Further, the secondary-side supercooling expansion valve 48a is subjected to opening degree control in such a manner that the supercooling degree of the secondary-side refrigerant flowing toward the secondary-side third communication pipe 7 at the outlet of the secondary-side supercooling heat exchanger 47 becomes a prescribed value. The bypass expansion valve 46a is controlled to the closed state. In the utilization units 3a, 3b, 3c, the utilization-side expansion valves 51a, 51b, 51c are subjected to opening degree adjustment.

[0163] In the above-described secondary-side refrigerant circuit 10, a part of the secondary-side high-pressure refrigerant compressed and discharged in the secondary-side compressor 21 is delivered to the secondary-side first communication pipe 8 via the secondary-side switching mechanism 22, the first heat source pipe 28, and the first shutoff valve 32, and the rest is delivered to the secondary-side flow path 35a of the cascade heat exchanger 35 via the secondary-side switching mechanism 22 and the third heat source pipe 25.

[0164] Next, the high-pressure refrigerant delivered to the secondary-side first communication pipe 8 is delivered to the first branch pipe 63c. The high-pressure refrigerant delivered to the first branch pipe 63c is delivered to the utilization-side heat exchanger 52c of the utilization unit 3c via the first adjustment valve 66c and the merging pipe 62c.

[0165] Next, the high-pressure refrigerant that has flowed through the second branch connection pipe 16c is branched into the third branch pipes 61c of the branch units 6c. The refrigerant that has flowed through the third branch pipes 61c is supplied to the second utilization pipes 56a, 56b of the first and second utilization units 3a, 3b.

[0166] Next, the refrigerant that has flowed through the third branch pipes 61c is supplied to the second utilization pipes 56a, 56b of the first and second utilization units 3a, 3b.

[0167] Further, the high-pressure refrigerant that has flowed into the secondary-side flow path 35a of the cascade heat exchanger 35 exchanges heat with the primary-side refrigerant that has flowed into the primary-side flow path 35b in the cascade heat exchanger 35, and thereby releases heat. The secondary-side refrigerant that has released heat in the cascade heat exchanger 35 flows into the secondary-side receiver 45 after the flow rate thereof is adjusted by the heat-source-side expansion valve 36. A part of the refrigerant that has flowed out of the secondary-side receiver 45 flows into the secondary-side subcooling circuit 48, and after the pressure thereof is reduced by the secondary-side subcooling expansion valve 48a, the refrigerant merges with the secondary-side suction flow path 23. Another part of the refrigerant that has flowed out of the secondary-side receiver 45 is cooled by the refrigerant that has flowed in the secondary-side subcooling circuit 48 in the secondary-side subcooling heat exchanger 47, and then passes through the third stop valve 31, and is supplied to the secondary-side third communication pipe 7 to merge with the refrigerant that has released heat in the utilization-side heat exchanger 52c.

[0168] Next, the refrigerant that has merged in the secondary-side third communication pipe 7 is branched into the third branch pipes 61a, 61b of the second branch units 6a, 6b. Then, the refrigerant that has flowed through the second branch connection pipes 16a, 16b is supplied to the second utilization pipes 56a, 56b of the first and second utilization units 3a, 3b. The refrigerant that has flowed through the second utilization pipes 56a, 56b passes through the utilization-side expansion valves 51a, 51b of the utilization units 3a, 3b.

[0169] Next, the refrigerant that has passed through the utilization-side expansion valves 51a, 51b whose opening degrees have been adjusted exchanges heat with the indoor air that has been supplied by the indoor fans 53a, 53b in the utilization-side heat exchangers 52a, 52b. Thus, the refrigerant that has flowed through the utilization-side heat exchangers 52a, 52b evaporates and becomes low-pressure gas refrigerant. The indoor air is cooled and supplied to the indoor. Thus, the indoor space is cooled. The low-pressure gas refrigerant that has evaporated in the utilization-side heat exchangers 52a, 52b is supplied to the merging pipes 62a, 62b of the first and second branch units 6a, 6b.

[0170] Then, the low-pressure refrigerant delivered to the confluence pipes 62a and 62b is delivered to the secondary side second connecting pipe 9 and confluenced through the second regulating valves 67a and 67b and the second branch pipes 64a and 64b.

[0171] Next, the low-pressure gaseous refrigerant delivered to the secondary side second connecting pipe 9 returns to the suction side of the secondary side compressor 21 through the second shut-off valve 33, the second heat source piping 29, the secondary side suction flow path 23, and the secondary side storage tank 30.

[0172] In this way, the refrigeration unit operates.

[0173] (9-4) Operation of the heating unit

[0174] During the operation of the heating unit, for example, the following operation is performed: the heat exchangers 52a and 52b on the utilization side of units 3a and 3b function as radiators for the refrigerant, and the heat exchanger 52c on the utilization side functions as an evaporator for the refrigerant. During the operation of the heating unit, the cascaded heat exchanger 35 functions as an evaporator for the secondary refrigerant. During the operation of the heating unit, the primary refrigerant circuit 5a and the secondary refrigerant circuit 10 of the refrigeration cycle system 1 operate as follows: Figure 6 The structure shown is as described. Figure 6 The arrows marked in the primary refrigerant circuit 5a and the secondary refrigerant circuit 10 indicate the flow of refrigerant when the heating unit is in operation.

[0175] Specifically, in primary-side unit 5, by switching primary-side switching mechanism 72 to the sixth connection state, the cascaded heat exchanger 35 functions as a radiator for the primary-side refrigerant. The sixth connection state of primary-side switching mechanism 72 is... Figure 6The connection state of the primary side switching mechanism 72 is shown by the dotted line. Thus, in the primary side unit 5, the primary side refrigerant discharged from the primary side compressor 71, passing through the primary side switching mechanism 72 and the first gas shut-off valve 109, passes through the primary side second communication pipe 112 and the second gas shut-off valve 107, and is delivered to the primary side flow path 35b of the cascade heat exchanger 35. The refrigerant flowing in the primary side flow path 35b of the cascade heat exchanger 35 is condensed by heat exchange with the secondary side refrigerant flowing in the secondary side flow path 35a. The primary side refrigerant condensed in the cascade heat exchanger 35 flows in the order of the first connection pipe 115, the primary side second expansion valve 102 controlled to be in the fully open state, the second liquid shut-off valve 106, the primary side first communication pipe 111, the first liquid shut-off valve 108, the primary side subcooling heat exchanger 103, and is depressurized in the primary side first expansion valve 76. In addition, during the heating main operation, the primary side subcooling expansion valve 104a is controlled to be in the closed state, whereby the refrigerant does not flow in the primary side subcooling circuit 104, and thus heat exchange in the primary side subcooling heat exchanger 103 does not occur. In addition, the valve opening degree of the primary side first expansion valve 76 is controlled, for example, in such a manner that the degree of superheat of the refrigerant sucked into the primary side compressor 71 becomes a prescribed value. The refrigerant depressurized in the primary side first expansion valve 76 is evaporated by heat exchange with the outside air supplied from the primary side fan 75 in the primary side heat exchanger 74, passes through the primary side switching mechanism 72 and the primary side reservoir 105, and is sucked into the primary side compressor 71.

[0176] In the heat source unit 2, the secondary-side switching mechanism 22 is switched to the second connection state and the third connection state. The second connection state of the secondary-side switching mechanism 22 is a connection state in which the first switching valve 22a is in the closed state and the third switching valve 22c is in the open state. The third connection state of the secondary-side switching mechanism 22 is a connection state in which the second switching valve 22b is in the open state and the fourth switching valve 22d is in the closed state. Thereby, the cascade heat exchanger 35 functions as an evaporator of the secondary-side refrigerant. Further, the opening degree of the heat-source-side expansion valve 36 is adjusted. In the first to third branch units 6a, 6b, 6c, the first adjustment valves 66a, 66b and the second adjustment valve 67c are controlled to be in the open state, and the first adjustment valve 66c and the second adjustment valves 67a, 67b are controlled to be in the closed state. Thereby, the utilization-side heat exchangers 52a, 52b of the utilization units 3a, 3b function as radiators of the refrigerant, and the utilization-side heat exchanger 52c of the utilization unit 3c functions as an evaporator of the refrigerant. Further, the utilization-side heat exchanger 52c of the utilization unit 3c and the suction side of the secondary-side compressor 21 of the heat source unit 2 become connected via the first utilization pipe 57a, the first branch connection pipe 15c, the merging pipe 62c, the second branch pipe 64c, and the secondary-side second communication pipe 9. Further, the utilization-side heat exchangers 52a, 52b of the utilization units 3a, 3b and the discharge side of the secondary-side compressor 21 of the heat source unit 2 become connected via the discharge flow path 24, the first heat source pipe 28, the secondary-side first communication pipe 8, the first branch pipes 63a, 63b, the merging pipes 62a, 62b, the first branch connection pipes 15a, 15b, and the first utilization pipes 57a, 57b. Further, the secondary-side subcooling expansion valve 48a and the bypass expansion valve 46a are controlled to be in the closed state. In the utilization units 3a, 3b, 3c, the utilization-side expansion valves 51a, 51b, 51c are adjusted in the opening degree.

[0177] Thus, in the secondary-side refrigerant circuit 10 described above, the secondary-side high-pressure refrigerant compressed and discharged by the secondary-side compressor 21 is sent to the secondary-side first communication pipe 8 via the secondary-side switching mechanism 22, the first heat source pipe 28, and the first shutoff valve 32.

[0178] Next, the high-pressure refrigerant sent to the secondary-side first communication pipe 8 is branched into two and sent to the first branch pipes 63a, 63b of the first branch unit 6a and the second branch unit 6b connected to the first utilization unit 3a and the second utilization unit 3b, respectively, which are the utilization units in operation. The high-pressure refrigerant sent to the first branch pipes 63a, 63b is sent to the utilization-side heat exchangers 52a, 52b of the first utilization unit 3a and the second utilization unit 3b via the first adjustment valves 66a, 66b, the merging pipes 62a, 62b, and the first branch connection pipes 15a, 15b.

[0179] Next, the high-pressure refrigerant delivered to the utilization-side heat exchangers 52a, 52b exchanges heat with indoor air supplied by the indoor fans 53a, 53b in the utilization-side heat exchangers 52a, 52b. Thus, the refrigerant flowing in the utilization-side heat exchangers 52a, 52b is radiated. The indoor air is heated and supplied to the indoor. Thus, the indoor space is heated. The refrigerant radiated in the utilization-side heat exchangers 52a, 52b flows in the second utilization pipes 56a, 56b, and passes through the utilization-side expansion valves 51a, 51b which are adjusted in opening degree. Then, the refrigerant flowing in the second branch connection pipes 16a, 16b is delivered to the secondary-side third communicating pipe 7 via the third branch pipes 61a, 61b of the branch units 6a, 6b.

[0180] Next, a part of the refrigerant delivered to the secondary-side third communicating pipe 7 is delivered to the third branch pipe 61c of the branch unit 6c, and the rest is delivered to the heat-source-side expansion valve 36 through the third stop valve 31.

[0181] Next, the refrigerant delivered to the third branch pipe 61c flows in the second utilization pipe 56c of the utilization unit 3c via the second branch connection pipe 16c, and is delivered to the utilization-side expansion valve 51c.

[0182] Next, the refrigerant passing through the utilization-side expansion valve 51c which is adjusted in opening degree exchanges heat with indoor air supplied by the indoor fan 53c in the utilization-side heat exchanger 52c. Thus, the refrigerant flowing in the utilization-side heat exchanger 52c evaporates and becomes low-pressure gas refrigerant. The indoor air is cooled and supplied to the indoor. Thus, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the utilization-side heat exchanger 52c is delivered to the merging pipe 62c via the first utilization pipe 57c and the first branch connection pipe 15c.

[0183] Next, the low-pressure gas refrigerant delivered to the merging pipe 62c is delivered to the secondary-side second communicating pipe 9 through the second adjustment valve 67c and the second branch pipe 64c.

[0184] Next, the low-pressure gas refrigerant delivered to the secondary-side second communicating pipe 9 is returned to the suction side of the secondary-side compressor 21 through the second stop valve 33, the second heat-source pipe 29, the secondary-side suction flow path 23, and the secondary-side accumulator 30.

[0185] Further, the refrigerant delivered to the heat-source-side expansion valve 36 exchanges heat with the primary-side refrigerant flowing in the primary-side flow path 35b in the secondary-side flow path 35a of the cascade heat exchanger 35 after passing through the heat-source-side expansion valve 36 whose opening degree is adjusted. Thus, the refrigerant flowing in the secondary-side flow path 35a of the cascade heat exchanger 35 evaporates to become low-pressure gas refrigerant and is delivered to the secondary-side switching mechanism 22. The low-pressure gas refrigerant delivered to the secondary-side switching mechanism 22 merges with the low-pressure gas refrigerant evaporated in the utilization-side heat exchanger 52c in the secondary-side suction flow path 23. The merged refrigerant returns to the suction side of the secondary-side compressor 21 via the secondary-side accumulator 30.

[0186] Thus, the operation in the heating main operation is performed.

[0187] (10) Residual refrigerant control

[0188] Figure 7 A flowchart of the residual refrigerant control is shown.

[0189] The residual refrigerant control is control for suppressing a decrease in the heat exchange efficiency of the cascade heat exchanger 35 due to stagnation of the liquid primary-side refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35. In the present embodiment, the residual refrigerant control is performed by satisfying a prescribed start condition when the heating operation or the heating main operation is performed.

[0190] Further, the residual refrigerant control performed by satisfying a prescribed condition when the heating operation is performed will be described below. Further, Figure 8 The form of the flow of the primary-side refrigerant and the secondary-side refrigerant of the refrigeration cycle system 1 in the residual refrigerant control is shown.

[0191] In step S1, the control unit 80 performs the heating operation in the refrigeration cycle system 1.

[0192] In the primary-side refrigerant circuit 5a, the primary-side controller 70 of the control portion 80 performs control of each portion of the primary-side unit 5. Here, the primary-side controller 70 controls the rotation speed of the primary-side compressor 71 in such a manner that the condensing temperature of the primary-side refrigerant condensed in the primary-side flow path 35b of the cascade heat exchanger 35 reaches a prescribed condensing temperature target value. Specifically, the primary-side controller 70 controls the rotation speed of the primary-side compressor 71 in such a manner that the saturation temperature of the primary-side refrigerant corresponding to the pressure of the primary-side refrigerant detected by the primary-side discharge pressure sensor 78 becomes the prescribed condensing temperature target value. Further, the primary-side control portion 70 controls the primary-side second expansion valve 102 to be in an open state and controls the primary-side subcooling expansion valve 104a to be in a closed state. Also, the primary-side control portion 70 controls the valve opening degree of the primary-side first expansion valve 76 in such a manner that the superheat degree of the primary-side refrigerant sucked into the primary-side compressor 71 becomes a prescribed value. Specifically, the primary-side control portion 70 controls the primary-side first expansion valve 76 in such a manner that the superheat degree obtained by subtracting the saturation temperature of the primary-side refrigerant corresponding to the pressure of the primary-side refrigerant detected by the primary-side suction pressure sensor 79 from the temperature of the primary-side refrigerant detected by the primary-side suction temperature sensor 81 becomes a prescribed value.

[0193] Further, in the secondary-side refrigerant circuit 10, the heat-source-side control portion 20 of the control portion 80 controls each portion of the heat-source unit 2, the branch unit control portions 60a, 60b, 60c of the control portion 80 control each portion of the branch units 6a, 6b, 6c, and the utilization-side control portions 50a, 50b, 50c of the control portion 80 control each portion of the utilization units 3a, 3b, 3c. Here, the heat-source-side control portion 20 controls the rotation speed of the secondary-side compressor 21 in such a manner that it becomes a rotation speed corresponding to the heat dissipation load in the utilization-side heat exchanger 52a, 52b, 52c. Further, the heat-source-side control portion 20 controls the secondary-side subcooling expansion valve 48a and the bypass expansion valve 46a to be in a closed state. Also, the heat-source-side control portion 20 controls the valve opening degree of the heat-source-side expansion valve 36 in such a manner that the superheat degree of the secondary-side refrigerant sucked into the secondary-side compressor 21 becomes a prescribed value. Specifically, the heat-source-side control portion 20 controls the heat-source-side expansion valve 36 in such a manner that the superheat degree obtained by subtracting the saturation temperature of the secondary-side refrigerant corresponding to the pressure of the secondary-side refrigerant detected by the secondary-side suction pressure sensor 37 from the temperature of the secondary-side refrigerant detected by the secondary-side suction temperature sensor 88 becomes a prescribed value. Further, the branch unit control portions 60a, 60b, 60c set the first regulating valves 66a, 66b, 66c to be in an open state and control the second regulating valves 67a, 67b, 67c to be in a closed state. Further, the utilization-side control portions 50a, 50b, 50c control the opening degrees of the utilization-side expansion valves 51a, 51b, 51c.

[0194] In step S2, the control unit 80 determines whether the prescribed start condition is satisfied by the refrigeration cycle system 1. The prescribed start condition determines whether the liquid state of the primary-side refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 is stagnated. In the present embodiment, when the degree of supercooling of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b of the cascade heat exchanger 35 becomes a prescribed value or more, it is determined that the prescribed start condition is satisfied. Specifically, the heat-source-side control unit 20 in the control unit 80 determines whether the degree of supercooling obtained by subtracting the temperature of the primary-side refrigerant detected by the primary-side first temperature sensor 121 from the condensation temperature of the primary-side refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 is a prescribed value or more. Here, in the present embodiment, the heat-source-side control unit 20 receives information of the detected pressure of the primary-side discharge pressure sensor 78 from the primary-side control unit 70, and thereby grasps the saturation temperature of the primary-side refrigerant corresponding to the pressure of the information as the condensation temperature of the primary-side refrigerant. Further, in a case where it is determined that the prescribed start condition is satisfied, the process proceeds to step S3, and in a case where it is determined that the prescribed start condition is not satisfied, the process continues to step S2.

[0195] In step S3, the control unit 80 starts the remaining refrigerant control. In the remaining refrigerant control, the primary-side control unit 70, which has received the information indicating that the prescribed start condition is satisfied from the heat-source-side control unit 20, controls the valve opening degree of the primary-side supercooling expansion valve 104a from the closed state to the fully open state in the control unit 80.

[0196] In step S4, the control unit 80 determines whether the prescribed end condition is satisfied by the refrigeration cycle system 1. The prescribed end condition determines whether the stagnation of the primary-side refrigerant in the liquid state in the primary-side flow path 35b of the cascade heat exchanger 35 is improved. In the present embodiment, when the degree of supercooling of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b of the cascade heat exchanger 35 is less than a prescribed value, it is determined that the prescribed end condition is satisfied. In addition, the prescribed value of the prescribed end condition can be set to a value smaller than the prescribed value of the prescribed start condition. Further, the determination of the degree of supercooling of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b is the same as that in step S2. Further, in a case where it is determined that the prescribed end condition is satisfied, the process proceeds to step S5, and in a case where it is determined that the prescribed end condition is not satisfied, the process continues to step S3.

[0197] In step S5, the control unit 80 ends the remaining refrigerant control. Specifically, the primary-side control unit 70 in the control unit 80 controls the valve opening degree of the primary-side supercooling expansion valve 104a to the closed state. Thereby, the refrigeration cycle system 1 returns to the operation state before the start of the remaining refrigerant control.

[0198] (11) Features of the Embodiment

[0199] In a refrigeration cycle system in which a binary refrigeration cycle is performed, primary-side refrigerant and secondary-side refrigerant are heat-exchanged in a cascade heat exchanger constituted by a plate heat exchanger or the like. Here, for example, when the temperature of the secondary-side refrigerant flowing into the cascade heat exchanger decreases due to a load variation of a utilization side or the like, and the subcooling degree of the primary-side refrigerant in the cascade heat exchanger increases, the area occupied by liquid refrigerant in the primary-side flow path as a whole in the cascade heat exchanger increases. Therefore, in the cascade heat exchanger, the area in which the primary-side refrigerant can undergo a phase change becomes smaller due to heat exchange with the secondary-side refrigerant, and the heat exchange efficiency decreases. In this way, the primary-side gas refrigerant delivered to the primary-side flow path of the cascade heat exchanger is difficult to condense, and the high pressure in the primary-side refrigerant circuit easily increases. Thus, the primary-side compressor that performs control to maintain the condensing pressure constant is controlled to decrease in rotational speed to suppress the increase in the high pressure. Here, the circulation amount of the primary-side refrigerant in the primary-side refrigerant circuit decreases, and the circulation amount of the secondary-side refrigerant in the secondary-side refrigerant circuit does not change, and thus the primary-side refrigerant flowing in the primary-side flow path of the cascade heat exchanger is further cooled by the secondary-side refrigerant. Therefore, the proportion of the primary-side refrigerant in a liquid state in the primary-side flow path of the cascade heat exchanger further increases.

[0200] Especially, in a refrigeration cycle system in which a binary refrigeration cycle is performed, in a case where the circulation amount of the secondary-side refrigerant in the secondary-side refrigerant circuit is controlled in accordance with the load in the utilization-side heat exchanger of the secondary-side refrigerant circuit, even if the circulation amount of the primary-side refrigerant in the primary-side refrigerant circuit decreases, adjustment of the circulation amount of the secondary-side refrigerant in accordance with the decrease in the circulation amount of the primary-side refrigerant is difficult to perform, and thus the condition in which the proportion of the primary-side refrigerant in a liquid state in the primary-side flow path of the cascade heat exchanger increases is difficult to eliminate.

[0201] Further, in a case where the filling amount of the primary-side refrigerant preliminarily filled in the primary-side refrigerant circuit is large, the above condition is easily generated. Further, in a case where a receiver capable of storing remaining refrigerant in the flow path of the liquid refrigerant of the primary-side refrigerant circuit is not provided, the above condition is sometimes particularly difficult to eliminate.

[0202] To this end, in the refrigeration cycle system 1 of the present embodiment, during the heating operation and the main heating operation in which the primary-side flow path 35b of the cascade heat exchanger 35 functions as a condenser of the primary-side refrigerant, the occurrence of the stagnation of the primary-side liquid refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 is grasped by satisfying a prescribed start condition. In the present embodiment, in a case where the subcooling degree of the primary-side liquid refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 is equal to or higher than a prescribed value, it is determined that the stagnation occurs. This is because, in a case where the primary-side liquid refrigerant stagnates in the primary-side flow path 35b of the cascade heat exchanger 35, the primary-side refrigerant condensed in the primary-side flow path 35b is difficult to flow out of the primary-side flow path 35b, and the time taken to be cooled by the secondary-side refrigerant flowing in the secondary-side flow path 35a becomes long, and thus, the subcooling degree of the primary-side liquid refrigerant in the primary-side flow path 35b increases. Also, in the refrigeration cycle system 1 of the present embodiment, when the occurrence of the stagnation of the primary-side liquid refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 is grasped as such, the remaining refrigerant control is started. In the remaining refrigerant control, a state in which the region in which the liquid refrigerant flows in the primary-side refrigerant circuit 5a is connected to the suction side of the primary-side compressor 71 via the primary-side subcooling circuit 104 is brought about. Thus, the stagnating primary-side liquid refrigerant flows to the suction side of the primary-side compressor 71, and the stagnation of the primary-side refrigerant in the primary-side flow path 35b can be eliminated. Thereby, the heat exchange efficiency of the primary-side refrigerant and the secondary-side refrigerant in the cascade heat exchanger 35 is improved.

[0203] Further, in the primary-side refrigerant circuit 5a, the primary-side subcooling circuit 104 is connected to the upstream side of the primary-side accumulator 105 provided to the primary-side suction flow path 125. Thus, in a case where the remaining refrigerant control is performed, the primary-side liquid refrigerant can also be stored in the primary-side accumulator 105, and thus, the liquid refrigerant can be prevented from being supplied to the primary-side compressor 71. In particular, in the remaining refrigerant control, even in a case where the primary-side subcooling expansion valve 104a is controlled to be in a fully open state so as to promptly eliminate the stagnation of the liquid refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35, the liquid refrigerant can be suppressed from being supplied to the primary-side compressor 71.

[0204] Also, in the refrigeration cycle system 1 of the present embodiment described above, in a case where carbon dioxide refrigerant is used as the refrigerant in the secondary-side refrigerant circuit 10, the global warming coefficient (GWP) can be suppressed to be low. Further, even in a case where refrigerant leakage occurs at the utilization side, since the refrigerant does not contain freon, the freon does not flow out at the utilization side.

[0205] Further, in the refrigeration cycle system 1 of the present embodiment described above, a binary refrigeration cycle is adopted, and thus, sufficient capacity can be obtained in the secondary-side refrigerant circuit 10.

[0206] (12) Other Embodiments

[0207] (12-1) Other Embodiments A

[0208] In the above embodiment, the case where the primary-side supercooling expansion valve 104a is opened when the surplus refrigerant control is performed is described as an example.

[0209] In this regard, as shown in FIG. 12, instead of or in addition to the primary-side supercooling circuit 104, the primary-side supercooling expansion valve 104a, and the primary-side supercooling heat exchanger 103 in the primary-side refrigerant circuit 5a of the above embodiment, a primary-side connection circuit 134 (corresponding to a bypass circuit) and a primary-side connection expansion valve 134a (corresponding to a control valve) can be included. Figure 9 The primary-side connection circuit 134 is a circuit that connects the second liquid connection pipe 126b in the liquid connection pipe 126 and the first suction flow path 125a in the primary-side suction flow path 125. The primary-side connection expansion valve 134a is provided in the primary-side connection circuit 134 and is an electric expansion valve that can perform opening degree adjustment to adjust the amount of primary-side refrigerant passing through the primary-side connection circuit 134.

[0210] Further, when the surplus refrigerant control is performed, the primary-side connection expansion valve 134a is controlled to be opened, and the primary-side refrigerant is caused to flow in the primary-side connection circuit 134, thereby exerting the same effects as the above embodiment.

[0211] (12-2) Other Embodiments B

[0212] In the above embodiment, the case where the primary-side supercooling expansion valve 104a is opened when the surplus refrigerant control is performed is described as an example.

[0213] In this regard, as shown in FIG. 13, instead of or in addition to the primary-side supercooling circuit 104, the primary-side supercooling expansion valve 104a, and the primary-side supercooling heat exchanger 103 in the primary-side refrigerant circuit 5a of the above embodiment, a primary-side receiver 145, a primary-side bypass circuit 144 (corresponding to a bypass circuit), and a primary-side bypass expansion valve 144a (corresponding to a control valve) can be included.

[0214] Figure 10

[0215] ​​The primary-side receiver 145 is a refrigerant container provided in the second liquid connection pipe 126b of the liquid connection pipe 126 and is capable of storing the primary-side refrigerant. A pipe connecting the inside of the primary-side receiver 145 and the primary-side first expansion valve 76 in the second liquid connection pipe 126b, a pipe connecting the inside of the primary-side receiver 145 and the first liquid shut-off valve 108 in the second liquid connection pipe 126b, and the primary-side bypass circuit 144 extend from the primary-side receiver 145. The primary-side bypass circuit 144 is a circuit extending from a gas phase region inside the primary-side receiver 145 and connecting with the first suction flow path 125a in the primary-side suction flow path 125. The primary-side bypass expansion valve 144a is provided in the primary-side bypass circuit 144 and is an electric expansion valve capable of adjusting the opening degree to adjust the amount of the primary-side refrigerant passing through the primary-side bypass circuit 144.

[0216] Also, when the remaining refrigerant control is performed, the control of opening the primary-side bypass expansion valve 144a is performed to cause the primary-side refrigerant to flow in the primary-side bypass circuit 144, thereby exerting the same effects as the above-described embodiment. Also, by including the primary-side receiver 145 in the primary-side refrigerant circuit 5a, it is possible to make it less likely that the liquid refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 is trapped.

[0217] (12-3) Other Embodiment C

[0218] In the above-described embodiment, the case where the valve opening degree of the primary-side subcooling expansion valve 104a is set to full opening at the time of the remaining refrigerant control is exemplified.

[0219] In this regard, in the remaining refrigerant control, the valve opening degree of the primary-side subcooling expansion valve 104a of the above-described embodiment, the primary-side connection expansion valve 134a of the above-described other embodiment A, and the primary-side bypass expansion valve 144a of the above-described other embodiment B can not be set to full opening, but can be controlled to a prescribed opening degree.

[0220] For example, it can be that, in the remaining refrigerant control, the primary-side subcooling expansion valve 104a, the primary-side connection expansion valve 134a, and the primary-side bypass expansion valve 144a are controlled in such a manner that the degree of superheat of the primary-side refrigerant sucked into the primary-side compressor 71 becomes a prescribed value.

[0221] Further, for example, in the remaining refrigerant control, the valve opening degree of the primary-side subcooling expansion valve 104a, the primary-side connection expansion valve 134a, and the primary-side bypass expansion valve 144a can be controlled in accordance with the degree of supercooling of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b of the cascade heat exchanger 35. Specifically, here, the primary-side subcooling expansion valve 104a, the primary-side connection expansion valve 134a, and the primary-side bypass expansion valve 144a can be controlled in such a manner that the larger the degree of supercooling of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b of the cascade heat exchanger 35, the larger the valve opening degree.

[0222] (12-4) Other Embodiment D

[0223] In the above-described embodiment, a case where the valve opening degree of the primary-side subcooling expansion valve 104a is controlled to the fully open state by the remaining refrigerant control is exemplified.

[0224] In this regard, in the remaining refrigerant control, not only the primary-side subcooling expansion valve 104a but also the rotational speed of the secondary-side compressor 21 can be controlled. For example, by controlling the rotational speed of the secondary-side compressor 21 to be lower than the rotational speed at the time when the prescribed start condition is satisfied, the heat exchange between the primary-side refrigerant and the secondary-side refrigerant in the cascade heat exchanger 35 is suppressed, and the degree of supercooling of the primary-side refrigerant in the primary-side flow path 35b can be suppressed to be small. Thus, the state where the primary-side liquid refrigerant stagnates in the primary-side flow path 35b of the cascade heat exchanger 35 can be suppressed.

[0225] Further, in the remaining refrigerant control, it is preferable that the control of the valve opening degree of the primary-side subcooling expansion valve 104a be given priority over the control of lowering the rotational speed of the secondary-side compressor 21. For example, after the control of increasing the valve opening degree of the primary-side subcooling expansion valve 104a or the control of setting the opening degree to the fully open state is performed, in a case where the state where the prescribed start condition is satisfied continues for a prescribed time or in a case where the state where the prescribed end condition is satisfied cannot be achieved even for a prescribed time, the control of lowering the rotational speed of the secondary-side compressor 21 can be started.

[0226] (12-5) Other Embodiment E

[0227] In the above-described embodiment, a case where the remaining refrigerant control is ended when the degree of supercooling of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b of the cascade heat exchanger 35 is smaller than a prescribed value is exemplified.

[0228] In this regard, the condition for ending the remaining refrigerant control is not limited to this, and for example, the remaining refrigerant control can be ended in a case where a prescribed time elapses after the remaining refrigerant control is started.

[0229] (12-6) Other Embodiment F

[0230] In the above-described embodiments, the case where the residual refrigerant control is started when the subcooling degree of the primary-side refrigerant flowing at the outlet of the primary-side flow path 35b of the cascade heat exchanger 35 is equal to or greater than a prescribed value is exemplified.

[0231] In this regard, the prescribed condition for starting the residual refrigerant control is not limited to this, and can be other conditions as described below.

[0232] For example, the prescribed start condition can also be that a value obtained by subtracting the low-pressure pressure of the secondary-side refrigerant in the secondary-side refrigerant circuit 10 from the high-pressure pressure of the primary-side refrigerant in the primary-side refrigerant circuit 5a is equal to or greater than a prescribed value. In this case, for example, the heat-source side control unit 20 that has received information of the detected pressure of the primary-side discharge pressure sensor 78 can grasp the pressure of the information as the high-pressure pressure of the primary-side refrigerant. Also, the heat-source side control unit 20 can judge whether or not a value obtained by subtracting the low-pressure pressure of the secondary-side refrigerant detected by the secondary-side suction pressure sensor 37 from the high-pressure pressure of the primary-side refrigerant is equal to or greater than a prescribed value, thereby judging the prescribed start condition.

[0233] Further, for example, the prescribed start condition can also be that the value obtained by subtracting the evaporation temperature of the secondary-side refrigerant in the secondary-side refrigerant circuit 10 from the condensation temperature of the primary-side refrigerant in the primary-side refrigerant circuit 5a is a prescribed value or more. In this case, for example, the heat source-side control portion 20 that receives information of the detected pressure of the primary-side discharge pressure sensor 78 from the primary-side control portion 70 grasps the saturation temperature of the primary-side refrigerant corresponding to the pressure of the information as the condensation temperature of the primary-side refrigerant. Further, it can also be that the heat source-side control portion 20 grasps the saturation temperature corresponding to the pressure of the secondary-side refrigerant detected by the secondary-side suction pressure sensor 37 as the evaporation temperature of the secondary-side refrigerant. Also, it can be that the heat source-side control portion 20 judges whether or not the value obtained by subtracting the evaporation temperature of the secondary-side refrigerant from the condensation temperature of the primary-side refrigerant is a prescribed value or more, thereby judging the prescribed start condition. In addition, in the case where the refrigerant temperature-pressure characteristics are different between the primary-side refrigerant and the secondary-side refrigerant, it is preferable to judge the prescribed start condition by the difference between the primary-side refrigerant temperature corresponding to the high-pressure pressure of the primary-side refrigerant and the secondary-side refrigerant temperature corresponding to the low-pressure pressure of the secondary-side refrigerant, as compared to judging the prescribed start condition by the difference between the high-pressure pressure of the primary-side refrigerant and the low-pressure pressure of the secondary-side refrigerant. This is because it is easier to more accurately grasp the case where the primary-side liquid refrigerant stagnation occurs in the primary-side flow path 35b of the cascade heat exchanger 35. Further, in the cascade heat exchanger 35 constituted by a plate heat exchanger or the like, there are cases where it is difficult to provide a temperature sensor for detecting the refrigerant temperature at the intermediate position of the primary-side flow path 35b and the refrigerant temperature at the intermediate position of the secondary-side flow path 35a, and therefore, it is preferable to judge using the temperature of the refrigerant obtained by conversion from the refrigerant pressure. In addition, when the heating operation or the heating main operation is performed in the secondary-side refrigerant circuit 10, the heat source-side control portion 20 controls the valve opening degree of the heat source-side expansion valve 36 so that the superheat degree of the secondary-side refrigerant sucked into the secondary-side compressor 21 is a prescribed value or more. Here, in the cascade heat exchanger 35, if the primary-side liquid refrigerant stagnation occurs in the primary-side flow path 35b, it is difficult to sufficiently evaporate the secondary-side refrigerant flowing in the secondary-side flow path 35a, and the superheat degree of the secondary-side refrigerant easily decreases. In this way, the heat source-side control portion 20 controls so as to close the valve opening degree of the heat source-side expansion valve 36 in order to suppress the decrease in the superheat degree of the secondary-side refrigerant, and therefore, the low-pressure pressure of the secondary-side refrigerant decreases, and the evaporation temperature of the secondary-side refrigerant decreases. Therefore, in the case where the value obtained by subtracting the evaporation temperature of the secondary-side refrigerant from the condensation temperature of the primary-side refrigerant increases, it can be presumed that the primary-side liquid refrigerant stagnation occurs in the primary-side flow path 35b of the cascade heat exchanger 35.

[0234] Further, for example, the prescribed start condition can also be that a value obtained by subtracting the temperature of the secondary-side refrigerant flowing into the secondary-side flow path 35a of the cascade heat exchanger 35 from the condensing temperature of the primary-side refrigerant in the primary-side refrigerant circuit 5a is a prescribed value or more. In this case, for example, the heat source-side control unit 20 that receives information of the detected pressure of the primary-side discharge pressure sensor 78 from the primary-side control unit 70 grasps the saturation temperature of the primary-side refrigerant corresponding to the pressure of the information as the condensing temperature of the primary-side refrigerant. Also, it can be that the heat source-side control unit 20 judges whether or not a value obtained by subtracting the temperature of the secondary-side refrigerant detected by the secondary-side first temperature sensor 83 from the condensing temperature of the primary-side refrigerant is a prescribed value or more, thereby judging the prescribed start condition. In addition, the temperature reduction of the secondary-side refrigerant flowing into the secondary-side flow path 35a occurs in correspondence with the reduction of the low-pressure pressure of the secondary-side refrigerant and the reduction of the evaporation temperature of the secondary-side refrigerant.

[0235] (12-7) Other Embodiment G

[0236] In the above-described embodiments, the case where the residual refrigerant control is started when the degree of subcooling of the primary-side refrigerant flowing out of the primary-side flow path 35b of the cascade heat exchanger 35 is a prescribed value or more has been described as an example.

[0237] In this regard, the prescribed start condition where the residual refrigerant control is started is not limited to this, and for example, the heat source-side control unit 20 can judge only from the sensors included in the heat source unit 2 as with the other conditions described below. That is, it can be that the heat source-side control unit 20 can judge the prescribed start condition without obtaining information from the primary-side control unit 70 of the primary-side unit 5.

[0238] For example, the prescribed start condition can also be that the difference between the temperature of the primary-side refrigerant flowing out of the primary-side flow path 35b of the cascade heat exchanger 35 and the temperature of the secondary-side refrigerant flowing into the secondary-side flow path 35a of the cascade heat exchanger 35 is a prescribed value or less. In this case, for example, it can be that the heat source-side control unit 20 judges whether or not a value obtained by subtracting the temperature detected by the secondary-side first temperature sensor 83 from the temperature detected by the primary-side first temperature sensor 121 is a prescribed value or less, thereby judging the prescribed start condition. Here, in the cascade heat exchanger 35, in the case where the temperature difference between the primary-side refrigerant flowing out of the primary-side flow path 35b and the secondary-side refrigerant flowing into the secondary-side flow path 35a becomes small, it can be presumed that the primary-side refrigerant of the primary-side flow path 35b is in a state of being excessively cooled and is in a state of being trapped in the cascade heat exchanger 35.

[0239] Further, the prescribed start condition can be, for example, that the degree of superheat of the secondary-side refrigerant suctioned by the secondary-side compressor 21 is equal to or lower than a prescribed value. In this case, for example, the heat-source-side control portion 20 can grasp the saturation temperature of the secondary-side refrigerant corresponding to the secondary-side refrigerant pressure detected by the secondary-side suction pressure sensor 37. Also, the heat-source-side control portion 20 judges whether or not the value obtained by subtracting the secondary-side refrigerant temperature detected by the secondary-side suction temperature sensor 88 from the saturation temperature is equal to or higher than a prescribed value, thereby judging the prescribed start condition. Here, in the case where the degree of superheat of the secondary-side refrigerant suctioned by the secondary-side compressor 21 is small, it can be presumed that the state where the primary-side liquid refrigerant is stagnated in the primary-side flow path 35b is present, because the secondary-side refrigerant is not sufficiently heated by the primary-side refrigerant in the secondary-side flow path 35a of the cascade heat exchanger 35.

[0240] Further, the prescribed start condition can be, for example, that the valve opening degree of the heat-source-side expansion valve 36 is smaller than a prescribed opening degree. In this case, for example, the heat-source-side control portion 20 judges whether or not the control opening degree of the heat-source-side expansion valve 36 is smaller than a prescribed opening degree, thereby judging the prescribed start condition. Here, in the case where the secondary-side refrigerant circuit 10 performs the heating operation or the heating main operation, the heat-source-side expansion valve 36 is controlled so that the degree of superheat of the secondary-side refrigerant suctioned by the secondary-side compressor 21 becomes a prescribed value. Therefore, in the case where the secondary-side refrigerant and the primary-side refrigerant do not sufficiently exchange heat in the secondary-side flow path 35a of the cascade heat exchanger 35, and the secondary-side refrigerant suctioned by the secondary-side compressor 21 becomes a wet gas, the valve opening degree of the heat-source-side expansion valve 36 is controlled to be small. Thus, in the case where the valve opening degree of the heat-source-side expansion valve 36 is controlled to be small, it can be presumed that the state where the primary-side liquid refrigerant is stagnated in the primary-side flow path 35b is present.

[0241] According to the above prescribed judgment condition, the heat-source-side control portion 20 can judge the prescribed start condition using only the detection values of the sensors included in the heat-source unit 2. Therefore, the heat-source-side control portion 20 can judge the prescribed start condition without depending on the information of the sensors included in the primary-side unit 5. In particular, in the case where the primary-side control portion 70 of the primary-side unit 5 is designed not to transmit the detection values of the sensors included in the primary-side unit 5 to the heat-source-side control portion 20 of the heat-source unit 2, or the heat-source-side control portion 20 of the heat-source unit 2 is designed not to receive the information of the detection values of the sensors included in the primary-side unit 5 from the primary-side control portion 70 of the primary-side unit 5, the heat-source-side control portion 20 can also judge whether or not the prescribed start condition is satisfied.

[0242] In addition, in a case where the determination of the prescribed start condition is made by the heat source side control portion 20, the prescribed start condition described above is preferred from the viewpoint of accuracy of the determination, but can be the prescribed start condition listed below. Specifically, the heat source side control portion 20 can determine the prescribed start condition by any one of the following: the pressure of the low-pressure refrigerant in the secondary side refrigerant circuit 10 is equal to or lower than a prescribed value; the evaporation temperature of the secondary side refrigerant in the secondary side refrigerant circuit 10 is equal to or lower than a prescribed value; the temperature of the secondary side refrigerant flowing into the secondary side flow path 35a of the cascade heat exchanger 35 is equal to or lower than a prescribed value; the pressure of the high-pressure refrigerant in the secondary side refrigerant circuit 10 is equal to or lower than a prescribed value; the condensation temperature of the secondary side refrigerant in the secondary side refrigerant circuit 10 is equal to or lower than a prescribed value; the temperature of the secondary side refrigerant sucked by the secondary side compressor 21 is equal to or lower than a prescribed value; and the temperature of the air passing through the utilization side heat exchangers 52a, 52b, 52c is equal to or lower than a prescribed value.

[0243] (12-8) Other Embodiment H

[0244] In the remaining refrigerant control of the above-described embodiment, a case where the primary side control portion 70 that has received the information indicating that the prescribed start condition is satisfied, which is transmitted from the heat source side control portion 20, controls the valve opening degree of the primary side supercooling expansion valve 104a is described as an example.

[0245] In this regard, in the remaining refrigerant control, the heat source side control portion 20 that has determined that the prescribed start condition is satisfied can directly control the valve opening degree of the primary side supercooling expansion valve 104a. The direct control referred to here means that the heat source side control portion 20 controls the valve opening degree of the primary side supercooling expansion valve 104a via the primary side control portion 70. Specifically, the heat source side control portion 20 transmits a control instruction to control the valve opening degree of the primary side supercooling expansion valve 104a to the primary side control portion 70, and the primary side control portion 70 transmits a control instruction of the valve opening degree of the primary side supercooling expansion valve 104a on the basis of the received control instruction.

[0246] In this way, the opening degree of the primary side supercooling expansion valve 104a can be controlled by the primary side control portion 70 other than at the time of the remaining refrigerant control, and can be controlled by the heat source side control portion 20 at the time of the remaining refrigerant control.

[0247] (12-9) Other Embodiment I

[0248] In the above-described embodiment, a case where the primary side control portion 70 that has received the information indicating that the prescribed start condition is satisfied, which is transmitted from the heat source side control portion 20, controls the valve opening degree of the primary side supercooling expansion valve 104a is described as an example.

[0249] To this end, the refrigeration cycle system 1 can also be a system configuration in which the primary-side control unit 70 cannot receive the information indicating that the prescribed start condition is satisfied, which is transmitted from the heat-source-side control unit 20, or a system configuration in which the heat-source-side control unit 20 cannot directly control the valve opening degree of the primary-side supercooling expansion valve 104a. Instead, the refrigeration cycle system 1 can be configured such that the heat-source-side control unit 20, which has grasped the situation in which the prescribed start condition is satisfied, indirectly instructs the primary-side control unit 70, so that the heat-source-side control unit 20 can indirectly control the valve opening degree of the primary-side supercooling expansion valve 104a.

[0250] For example, the above-described refrigeration cycle system 1 can be a system configuration in which the heat-source-side control unit 20 can transmit a control command of a condensing temperature target value of the primary-side refrigerant in the primary-side refrigerant circuit 5a to the primary-side control unit 70, and the primary-side control unit 70 can receive the control command of the condensing temperature target value transmitted from the heat-source-side control unit 20. Also, the primary-side control unit 70 can be configured to perform control to increase or fully open the valve opening degree of the primary-side supercooling expansion valve 104a in a case where the high-pressure pressure of the primary-side refrigerant in the primary-side refrigerant circuit 5a is equal to or higher than a prescribed value.

[0251] According to the above configuration, in a case where the heat-source-side control unit 20, which has grasped the situation in which the prescribed start condition is satisfied, transmits a control command to increase the condensing temperature target value of the primary-side refrigerant in the primary-side refrigerant circuit 5a to the primary-side control unit 70, the primary-side control unit 70 increases the rotation speed of the primary-side compressor 71 so as to achieve the increased condensing temperature target value. However, in the cascade heat exchanger 35 in the state in which the prescribed start condition is satisfied, the heat exchange efficiency between the primary-side refrigerant and the secondary-side refrigerant is reduced, and thus even if the primary-side high-pressure refrigerant is supplied to the primary-side flow path 35b of the cascade heat exchanger 35, the primary-side refrigerant cannot be efficiently condensed. Therefore, the high-pressure pressure of the primary-side refrigerant in the primary-side refrigerant circuit 5a is increased. Also, in a case where the high-pressure pressure of the primary-side refrigerant in the primary-side refrigerant circuit 5a is increased to be equal to or higher than a prescribed value as described above, the primary-side control unit 70 starts control to increase or fully open the valve opening degree of the primary-side supercooling expansion valve 104a. Thus, it is possible to improve the heat exchange efficiency between the primary-side refrigerant and the secondary-side refrigerant in the cascade heat exchanger 35.

[0252] In addition, for example, the primary-side unit 5 is not a structure specially designed for the refrigeration cycle system 1, but is a heat source unit in a refrigeration device that performs a single refrigeration cycle with a utilization unit having a utilization-side heat exchanger connected to the heat source unit having a heat source-side heat exchanger and a compressor. In this case, sometimes the primary-side control portion 70 cannot receive the information indicating that the prescribed start condition is satisfied transmitted from the heat source-side control portion 20, and cannot directly control the valve opening degree of the primary-side supercooling expansion valve 104a by the heat source-side control portion 20. In this case, in the refrigeration device that performs a single refrigeration cycle, sometimes a system structure is adopted in which the rotation speed of the compressor possessed by the heat source unit is controlled in accordance with the load in the utilization-side heat exchanger possessed by the utilization unit. In this system structure, a system structure is formed in which, in order to inform the heat source side of the load grasped by the utilization unit, a control instruction of a control target value such as a condensation temperature target value is transmitted from the utilization unit to the heat source unit. In the case where the heat source unit of the above-described refrigeration device that performs a single refrigeration cycle is used as the above-described primary-side unit 5, the primary-side control portion 70 of the primary-side unit 5 can receive the control instruction of the control target value such as the condensation temperature target value. Therefore, as the primary-side unit 5, a used heat source unit in a refrigeration device that performs a single refrigeration cycle, which cannot receive the information indicating that the prescribed start condition is satisfied from the heat source-side control portion 20 and cannot directly control the valve opening degree of the primary-side supercooling expansion valve 104a by the heat source-side control portion 20, can be used, and the remaining refrigerant control can be implemented.

[0253] Especially, in the refrigeration device that connects a plurality of utilization units to the heat source unit and performs a single refrigeration cycle, the amount of the primary-side refrigerant preliminarily filled in the heat source unit tends to be large, and the stagnation of the primary-side liquid refrigerant in the primary-side flow path 35b of the cascade heat exchanger 35 tends to occur. Thus, by using the heat source unit of the refrigeration device that performs a single refrigeration cycle for the refrigeration cycle system 1, even if the stagnation of the primary-side liquid refrigerant in the cascade heat exchanger 35 tends to occur, the stagnation of the liquid refrigerant can be eliminated by the above-described remaining refrigerant control.

[0254] (12-10) Other Embodiment J

[0255] In the above-described embodiment, R32 is exemplified as the refrigerant used in the primary-side refrigerant circuit 5a, and carbon dioxide is exemplified as the refrigerant used in the secondary-side refrigerant circuit 10.

[0256] In this regard, as the refrigerant used in the primary-side refrigerant circuit 5a, there is no particular limitation, and HFC-32, an HFO-based refrigerant, a mixed refrigerant of HFC-32 and an HFO-based refrigerant, carbon dioxide, ammonia, propane, or the like can be used.

[0257] Further, as the refrigerant used in the secondary-side refrigerant circuit 10, there is no particular limitation, and HFC-32, an HFO-based refrigerant, a mixed refrigerant of HFC-32 and an HFO-based refrigerant, carbon dioxide, ammonia, propane, or the like can be used.

[0258] Further, as the HFO-based refrigerant, for example, HFO-1234yf, HFO-1234ze, or the like can be used.

[0259] Further, in the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10, the same refrigerant can be used, or different refrigerants can be used.

[0260] (12-11) Other Embodiment K

[0261] In the above-described embodiments, as the secondary-side refrigerant circuit 10, a refrigerant circuit capable of simultaneous operation of cooling and heating having a three-tube type of secondary-side first communication pipe 8, secondary-side second communication pipe 9, and secondary-side third communication pipe 7 was exemplified.

[0262] In this regard, as the secondary-side refrigerant circuit 10, it is not limited to a refrigerant circuit capable of simultaneous operation of cooling and heating, and can be a circuit in which the heat source unit 2 and the utilization units 3a, 3b, 3c are connected via two communication pipes.

[0263] (Notes)

[0264] The above-described embodiments of the present disclosure have been described, but it should be understood that various modifications in form and details can be made without departing from the spirit and scope of the present disclosure recited in the claims.

[0265] Explanation of Symbols

[0266] 1: Refrigeration cycle system

[0267] 2: Heat source unit

[0268] 3a: First utilization unit

[0269] 3b: Second utilization unit

[0270] 3c: Third utilization unit

[0271] 4: Secondary-side unit

[0272] 5: Primary-side unit

[0273] 5a: Primary-side refrigerant circuit (first circuit)

[0274] 7: Secondary-side third communication pipe

[0275] 8: Secondary-side first communication pipe

[0276] 9: Secondary side third connecting pipe

[0277] 10: Secondary refrigerant circuit (secondary circuit)

[0278] 11: Expansion mechanism on the heat source side

[0279] 12: Heat source circuit

[0280] 13a-c: Using loops

[0281] 20: Heat source side control unit (second control unit)

[0282] 21: Secondary compressor (second compressor)

[0283] 21a: Compressor motor

[0284] 22: Secondary-side switching mechanism

[0285] 23: Secondary side suction flow path

[0286] 24: Discharge flow path

[0287] 25: Third heat source piping

[0288] 26: Fourth heat source piping

[0289] 27: Fifth heat source piping

[0290] 28: Primary heat source piping

[0291] 29: Second heat source piping

[0292] 30: Secondary side storage tank

[0293] 34: Oil separator

[0294] 35: Cascaded heat exchanger

[0295] 35a: Secondary side flow path

[0296] 35b: Primary side flow path

[0297] 36: Expansion valve on the heat source side (second expansion valve)

[0298] 37: Secondary side inhalation pressure sensor

[0299] 38: Secondary side discharge pressure sensor

[0300] 39: Secondary side discharge temperature sensor

[0301] 40: Oil return circuit

[0302] 41: Return oil flow path

[0303] 42: Oil return capillary

[0304] 44: oil return on-off valve

[0305] 45: secondary side receiver

[0306] 46: bypass circuit

[0307] 46a: bypass expansion valve

[0308] 47: secondary side subcooling heat exchanger

[0309] 48: secondary side subcooling circuit

[0310] 48a: secondary side subcooling expansion valve

[0311] 50a-c: utilization side control section

[0312] 51a-c: utilization side expansion valve

[0313] 52a-c: utilization side heat exchanger (second heat exchanger)

[0314] 53a-c: indoor fan

[0315] 56a, 56b, 56c: second utilization pipe

[0316] 57a, 57b, 57c: first utilization pipe

[0317] 58a, 58b, 58c: liquid side temperature sensor

[0318] 59a, 59b, 59c: indoor blow-out temperature sensor

[0319] 60a, 60b, 60c: branch unit control section

[0320] 61a, 61b, 61c: third branch pipe

[0321] 62a, 62b, 62c: merging pipe

[0322] 63a, 63b, 63c: first branch pipe

[0323] 64a, 64b, 64c: second branch pipe

[0324] 66a, 66b, 66c: first regulating valve

[0325] 67a, 67b, 67c: second regulating valve

[0326] 70: primary side control section (first control section)

[0327] 71: primary side compressor (first compressor)

[0328] 72: primary side switching mechanism

[0329] 74: primary-side heat exchanger (first heat exchanger)

[0330] 76: primary-side first expansion valve

[0331] 77: outdoor air temperature sensor

[0332] 78: primary-side discharge pressure sensor

[0333] 79: primary-side suction pressure sensor

[0334] 81: primary-side suction temperature sensor

[0335] 82: primary-side heat-exchange temperature sensor

[0336] 83: secondary-side first temperature sensor

[0337] 84: receiver outlet temperature sensor

[0338] 85: bypass circuit temperature sensor

[0339] 86: supercooling outlet temperature sensor

[0340] 87: supercooling circuit temperature sensor

[0341] 88: secondary-side suction temperature sensor

[0342] 80: control unit

[0343] 102: primary-side second expansion valve

[0344] 103: primary-side supercooling heat exchanger

[0345] 104: primary-side supercooling circuit (bypass circuit)

[0346] 104a: primary-side supercooling expansion valve (control valve)

[0347] 105: primary-side accumulator (accumulator)

[0348] 111: primary-side first communication pipe (first flow path)

[0349] 112: primary-side second communication pipe

[0350] 113: second connection pipe

[0351] 115: first connection pipe (first flow path)

[0352] 121: primary-side first temperature sensor

[0353] 122: primary-side second temperature sensor

[0354] 125: Primary-side suction flow path (suction flow path)

[0355] 125a: First suction flow path (first suction pipe)

[0356] 125b: Second suction flow path (second suction pipe)

[0357] 126: Liquid connection pipe (first flow path)

[0358] 134: Primary-side connection circuit (bypass circuit)

[0359] 134a: Primary-side connection expansion valve (control valve)

[0360] 144: Primary-side bypass circuit (bypass circuit)

[0361] 144a: Primary-side bypass expansion valve (control valve)

[0362] Prior art document

[0363] Patent document

[0364] Patent document 1: International Publication No. 2018 / 235832.

Claims

1. A refrigeration cycle system (1) characterized by, including: a first circuit (5a) that is a circuit in which a first refrigerant circulates, and that has a first compressor (71), a cascade heat exchanger (35), and a first heat exchanger (74); and a second circuit (10) that is a circuit in which a second refrigerant circulates, and that has a second compressor (21), the cascade heat exchanger (35), and a second heat exchanger (52a, 52b, 52c), the first circuit has: a first flow path (115, 111, 126) that connects the cascade heat exchanger and the first heat exchanger; a suction flow path (125) of the first compressor; a bypass circuit (104, 134, 144) that connects the first flow path and the suction flow path; and a control valve (104a, 134a, 144a) that is provided to the bypass circuit, when the cascade heat exchanger functions as a radiator of the first refrigerant and as an evaporator of the second refrigerant, the control valve is opened in a case where an index related to a degree of supercooling of the first refrigerant at an outlet of the cascade heat exchanger satisfies a prescribed first condition, the first condition is satisfied in a case where at least any one of a value obtained by subtracting a temperature of the first refrigerant flowing out of the cascade heat exchanger from a condensation temperature of the first refrigerant in the first circuit is a prescribed value or more; a value obtained by subtracting a pressure of low-pressure refrigerant in the second circuit from a pressure of high-pressure refrigerant in the first circuit is a prescribed value or more; a value obtained by subtracting an evaporation temperature of the second refrigerant in the second circuit from the condensation temperature of the first refrigerant in the first circuit is a prescribed value or more; a value obtained by subtracting a temperature of the second refrigerant flowing into the cascade heat exchanger from the condensation temperature of the first refrigerant in the first circuit is a prescribed value or more, a temperature-pressure characteristic of the first refrigerant is different from a temperature-pressure characteristic of the second refrigerant, the first condition is judged on the basis of a temperature difference between a temperature of the first refrigerant grasped from a pressure of the first refrigerant in the cascade heat exchanger and a temperature of the second refrigerant grasped from a pressure of the second refrigerant in the cascade heat exchanger.

2. A refrigeration cycle system (1) characterized by, including: a first circuit (5a) that is a circuit in which a first refrigerant circulates, and that has a first compressor (71), a cascade heat exchanger (35), and a first heat exchanger (74); and a second circuit (10) that is a circuit in which a second refrigerant circulates, and that has a second compressor (21), the cascade heat exchanger (35), and a second heat exchanger (52a, 52b, 52c), the first circuit has: a first flow path (115, 111, 126) that connects the cascade heat exchanger and the first heat exchanger; a suction flow path (125) of the first compressor; a bypass circuit (104, 134, 144) that connects the first flow path and the suction flow path; and a control valve (104a, 134a, 144a) that is provided to the bypass circuit, when the cascade heat exchanger functions as a radiator of the first refrigerant and as an evaporator of the second refrigerant, the control valve is opened in a case where an index related to a degree of supercooling of the first refrigerant at an outlet of the cascade heat exchanger satisfies a prescribed first condition, the first condition is satisfied in a case where at least any one of a value obtained by subtracting a temperature of the first refrigerant flowing out of the cascade heat exchanger from a condensation temperature of the first refrigerant in the first circuit is a prescribed value or more; a value obtained by subtracting a pressure of low-pressure refrigerant in the second circuit from a pressure of high-pressure refrigerant in the first circuit is a prescribed value or more; a value obtained by subtracting an evaporation temperature of the second refrigerant in the second circuit from the condensation temperature of the first refrigerant in the first circuit is a prescribed value or more; a value obtained by subtracting a temperature of the second refrigerant flowing into the cascade heat exchanger from the condensation temperature of the first refrigerant in the first circuit is a prescribed value or more, a temperature-pressure characteristic of the first refrigerant is different from a temperature-pressure characteristic of the second refrigerant, the first condition is judged on the basis of a temperature difference between a temperature of the first refrigerant grasped from a pressure of the first refrigerant in the cascade heat exchanger and a temperature of the second refrigerant grasped from a pressure of the second refrigerant in the cascade heat exchanger. The first circuit has: a first flow path (115, 111, 126) connecting the cascade heat exchanger and the first heat exchanger; a suction flow path (125) of the first compressor; a bypass circuit (104, 134, 144) connecting the first flow path and the suction flow path; and a control valve (104a, 134a, 144a) provided in the bypass circuit, The control valve is opened when an index related to a degree of supercooling of the first refrigerant at an outlet of the cascade heat exchanger satisfies a prescribed first condition while the cascade heat exchanger functions as a radiator of the first refrigerant and as an evaporator of the second refrigerant, The first condition is satisfied when at least any one of the following is satisfied, A difference between a temperature of the first refrigerant flowing out of the cascade heat exchanger and a temperature of the second refrigerant flowing into the cascade heat exchanger is equal to or lower than a prescribed value; A degree of superheat of the second refrigerant sucked into the second compressor is equal to or lower than a prescribed value; The second circuit has a second expansion valve (36) between the second heat exchanger and the cascade heat exchanger, a valve opening degree of the second expansion valve being varied according to a degree of superheat of the second refrigerant sucked into the second compressor, the opening degree of the second expansion valve being smaller than a prescribed opening degree.

3. A refrigeration cycle system (1) characterized by, Comprise: A first circuit (5a) that is a circuit in which a first refrigerant circulates, and that has a first compressor (71), a cascade heat exchanger (35), and a first heat exchanger (74); and A second circuit (10) that is a circuit in which a second refrigerant circulates, and that has a second compressor (21), the cascade heat exchanger (35), and a second heat exchanger (52a, 52b, 52c), The first circuit has: a first flow path (115, 111, 126) connecting the cascade heat exchanger and the first heat exchanger; a suction flow path (125) of the first compressor; a bypass circuit (104, 134, 144) connecting the first flow path and the suction flow path; and a control valve (104a, 134a, 144a) provided in the bypass circuit, The control valve is opened when an index related to a degree of supercooling of the first refrigerant at an outlet of the cascade heat exchanger satisfies a prescribed first condition while the cascade heat exchanger functions as a radiator of the first refrigerant and as an evaporator of the second refrigerant, The rotational speed of the second compressor is decreased when the first condition is satisfied.

4. The refrigeration cycle system according to claim 3, characterized by The first condition is satisfied when at least any one of the following is satisfied, A value obtained by subtracting a temperature of the first refrigerant flowing out of the cascade heat exchanger from a condensing temperature of the first refrigerant in the first circuit is equal to or higher than a prescribed value; A value obtained by subtracting a pressure of low-pressure refrigerant in the second circuit from a pressure of high-pressure refrigerant in the first circuit is equal to or higher than a prescribed value; a value obtained by subtracting the evaporation temperature of the second refrigerant in the second circuit from the condensation temperature of the first refrigerant in the first circuit is equal to or greater than a prescribed value; a value obtained by subtracting the temperature of the second refrigerant flowing into the cascade heat exchanger from the condensation temperature of the first refrigerant in the first circuit is equal to or greater than a prescribed value.

5. The refrigeration cycle system according to any one of claims 1 to 4, wherein the first circuit further has a reservoir (105), the suction flow path includes a first suction pipe (125a) and a second suction pipe (125b), the first suction pipe, the reservoir, the second suction pipe, and the first compressor are connected in this order, the bypass circuit is connected to the first suction pipe.

6. The refrigeration cycle system according to any one of claims 1 to 4, wherein the control valve is fully opened when the first condition is satisfied. Further comprising:

7. The refrigeration cycle system according to any one of claims 1 to 4, characterized by a first control unit (70) that performs control of the first circuit; and a second control unit (20) that performs control of the second circuit.

8. The refrigeration cycle system according to claim 7, wherein the second control unit outputs a control instruction of the control valve when the first condition is satisfied, the first control unit outputs a control instruction to the control valve when the first condition is not satisfied. ​ ​

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