Cascade unit and refrigeration system

Abstract

To provide a cascade unit improved in a degree of freedom in arranging pipes.SOLUTION: A cascade unit 2 is a cascade unit of a refrigeration system having a first circuit, a second circuit, and a cascade heat exchanger. The cascade unit includes the cascade heat exchanger, a second compressor, electric components, and a cascade casing 2x. The cascade casing 2x has a piping port O1 within a range from one end in a first direction to 1 / 3 of a width in the first direction. From the piping port O1, a first pipe and a second pipe connecting the cascade heat exchanger and a first heat exchanger of the first circuit, and a liquid pipe and a gas pipe connecting the cascade heat exchanger and a second heat exchanger of the second circuit are led out. The cascade casing 2x is provided with a wiring port O2 within a range from the other end in the first direction to 1 / 3 of the width in the first direction. From the wiring port O2, a wiring connected to the electric components is led out.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a cascade unit and a refrigeration system. [Background technology]

[0002] Patent Document 1 (JP 2012-193866 A) discloses a refrigeration system in which a high-temperature side refrigerant circulation circuit and a low-temperature side refrigerant circulation circuit are cascade-connected via a cascade condenser. The refrigeration system of Patent Document 1 includes an outdoor unit composed of a high-temperature side housing and a low-temperature side housing adjacent to each other. A high-temperature side service valve is disposed in the high-temperature side housing, and a low-temperature side service valve is disposed in the low-temperature side housing. Summary of the Invention [Problem to be solved by the invention]

[0003] The above-mentioned Patent Document 1 merely discloses a low-temperature side service valve in which piping of a low-temperature side refrigerant circulation circuit is connected to a low-temperature side housing that houses a cascade condenser. In the refrigeration device of the above-mentioned Patent Document 1, there is room for improvement in the arrangement of the refrigerant piping of the high-temperature side refrigerant circulation circuit and the low-temperature side circulation circuit. [Means for solving the problem]

[0004] A cascade unit according to a first aspect is a cascade unit of a refrigeration system having a first circuit, a second circuit, and a cascade heat exchanger. A heat medium for transporting heat flows through the first circuit. The first circuit has a first heat exchanger. The first heat exchanger exchanges heat between a heat source and the heat medium. The second circuit has a second compressor and a second heat exchanger. The second compressor compresses a second refrigerant. The second heat exchanger exchanges heat between the second refrigerant and indoor air. The second refrigerant circulates through the second circuit. The cascade heat exchanger exchanges heat between the heat medium of the first circuit and the second refrigerant of the second circuit. The cascade unit includes the cascade heat exchanger, the second compressor, an electrical component, and a casing. The electrical component drives the second compressor. The casing houses the cascade heat exchanger, the second compressor, and the electrical component. The casing has a piping opening formed in a range from one end in the first direction to 1 / 3 of the width in the first direction. The piping opening leads out a first pipe and a second pipe connecting the cascade heat exchanger of the first circuit to the first heat exchanger, and a liquid pipe and a gas pipe connecting the cascade heat exchanger of the second circuit to the second heat exchanger. The casing also has a wiring opening formed in a range from the other end in the first direction to 1 / 3 of the width in the first direction. The wiring opening leads out wiring connected to electrical equipment.

[0005] The inventors focused on the fact that piping and wiring are taken out from the cascade unit to both the external first unit having the first heat exchanger and the external second unit having the second heat exchanger, and found that there is a problem in that the degree of freedom in handling the piping is reduced when wiring is arranged near the piping, and thus completed the invention according to the present disclosure.

[0006] According to the cascade unit of the first aspect, the pipe openings for leading out the first pipe and the second pipe of the first circuit and the liquid pipe and the gas pipe of the second circuit, and the wiring openings for leading out the wiring are arranged apart in a first direction (e.g., left-right direction). Therefore, the first pipe, the second pipe, the liquid pipe, and the gas pipe (hereinafter also simply referred to as "pipes") can be collected at one end of the casing in the first direction, and the wiring can be collected at the other end of the casing in the second direction. This can reduce the constraints on the layout of the pipes due to the wiring. Therefore, the degree of freedom in layout of the pipes is increased.

[0007] A cascade unit according to a second aspect is the cascade unit of the first aspect, wherein the casing has a side surface extending in a first direction, and the piping port and the wiring port are formed on the side surface.

[0008] In the cascade unit according to the second aspect, the pipes can be collected in a range from one end of the side surface in the first direction to 1 / 3 of the width in the first direction, and the wiring ports can be collected in a range from the other end of the side surface in the first direction to 1 / 3 of the width in the first direction, thus providing a higher degree of freedom in the arrangement of the pipes.

[0009] A cascade unit according to a third aspect is the cascade unit according to the first or second aspect, wherein the cascade further includes a bottom plate constituting a bottom surface of the cascade unit, and the cascade heat exchanger is disposed near the pipe port and on the bottom plate.

[0010] In the cascade unit of the third aspect, the cascade heat exchanger is disposed near the piping port and on the bottom plate, so that the piping can be shortened and the cascade heat exchanger can be stably disposed.

[0011] A cascade unit according to a fourth aspect is the cascade unit according to the first to third aspects, wherein the cascade unit has a side surface extending in a first direction, and when viewed from the side, the electrical equipment and the cascade heat exchanger do not overlap.

[0012] As described above, the piping is drawn from the cascade heat exchanger to the piping port, and the wiring from the electrical equipment is drawn to the wiring port. In the cascade unit of the fourth aspect, since the electrical equipment and the cascade unit do not overlap in a side view, it is easy to realize an arrangement in which the piping port and the wiring port are separated in the first direction.

[0013] A cascade unit according to a fifth aspect is the cascade unit according to the first to fourth aspects, wherein the first pipe, the second pipe, the liquid pipe and the gas pipe are aligned in a plurality of different directions at the pipe port.

[0014] In the cascade unit of the fifth aspect, at the pipe port, the direction in which some of the four or more pipes in the casing are arranged (e.g., the vertical direction) differs from the direction in which the other parts are arranged (e.g., the horizontal direction). This makes it possible to easily gather the four or more pipes at the pipe port.

[0015] A cascade unit according to a sixth aspect is the cascade unit according to the first to fifth aspects, in which the piping port and the wiring port are disposed at one end in a second direction perpendicular to the first direction. The casing has an opening for maintenance formed on the other end side in the second direction closer to the piping port and the wiring port. The casing further has a removable plate member that closes the opening.

[0016] In the cascade unit of the sixth aspect, maintenance can be performed at the opening exposed by removing the plate material. Since the piping port is arranged at one end in the first direction and the wiring port is arranged at the other end in the first direction, closer to one end in the second direction than the opening, the piping and wiring do not protrude from the center. This improves the ease of maintenance through the opening.

[0017] A cascade unit according to a seventh aspect is the cascade unit according to any one of the first to sixth aspects, wherein the second refrigerant is carbon dioxide.

[0018] In the cascade unit of the seventh aspect, carbon dioxide is sealed in the refrigerant piping of the second circuit. The refrigerant piping in which carbon dioxide is sealed is required to have high pressure resistance, and therefore has a large wall thickness. When brazing is performed during construction, the heat input is large, and the work time is long. As described above, the wiring port is disposed on the other end side opposite the pipe port in the first direction, and therefore the wiring can be separated from the refrigerant piping in which carbon dioxide is sealed. This makes it possible to reduce the impact on the wiring caused by the long work time at the pipe port.

[0019] A refrigeration system according to an eighth aspect includes the cascade unit according to any one of the first to seventh aspects, a first unit, and a second unit. The first unit includes a first heat exchanger. The second unit includes a second heat exchanger.

[0020] In the refrigeration system of the eighth aspect, in the cascade unit, the piping ports for leading out the piping of the first and second circuits and the wiring ports for leading out the wiring are formed apart in the first direction. Therefore, in the cascade unit, restrictions on piping layout due to wiring can be reduced, and the degree of freedom in piping layout from the cascade unit to the first unit and the second unit is increased. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a refrigeration system. [Diagram 2] FIG. 2 is a schematic functional block diagram of the refrigeration system. [Diagram 3] FIG. 4 is a diagram showing the operation (flow of refrigerant) of the refrigeration system in cooling operation. [Figure 4] FIG. 4 is a diagram showing the operation (flow of refrigerant) of the refrigeration system in a heating operation. [Diagram 5] FIG. 2 is a diagram showing the operation (flow of refrigerant) in simultaneous cooling and heating operation (mainly cooling) of the refrigeration system. [Figure 6] FIG. 2 is a diagram showing the operation (flow of refrigerant) in simultaneous cooling and heating operation (mainly heating) of the refrigeration system. [Figure 7]FIG. 4 is a schematic diagram showing a state in which a first unit and a cascade unit are connected. [Figure 8] FIG. 2 is a perspective view showing a cascade unit casing. [Figure 9] FIG. 2 is a perspective view showing the inside of the cascade unit. [Figure 10] FIG. 2 is a schematic diagram of a cascade unit as viewed from the front. [Figure 11] FIG. 4 is a schematic diagram of a piping port of a casing of the cascade unit. [Figure 12] FIG. 4 is a schematic diagram of liquid and gas pipes near a shutoff valve of a cascade unit. [Figure 13] FIG. 11 is a schematic diagram showing a state in which a first unit and a cascade unit are connected in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] (1) Refrigeration system configuration A refrigeration system 1 shown in Figs. 1 and 2 is an apparatus used for cooling and heating the interior of a building or the like by performing a vapor compression refrigeration cycle operation.

[0023] The refrigeration system 1 has a first circuit (primary side circuit) 5a, a second circuit (secondary side circuit) 10, and a cascade heat exchanger 35. The first circuit 5a has a first heat exchanger 74. The second circuit 10 has a second compressor 21 and second heat exchangers 52a, 52b, and 52c. The refrigeration system 1 of this embodiment has a binary refrigerant circuit consisting of a vapor compression type first circuit 5a and a vapor compression type second circuit 10, and performs a binary refrigeration cycle.

[0024] In the first circuit 5a, a heat medium that transfers heat circulates. Here, the heat medium is a first refrigerant. The first refrigerant includes, for example, at least one of an HFC refrigerant and an HFO refrigerant. In the second circuit 10, a second refrigerant circulates. The second refrigerant includes, for example, carbon dioxide.

[0025] The first circuit 5a and the second circuit 10 are thermally connected via a cascade heat exchanger 35.

[0026] The first circuit 5a has a first pipe P1 and a second pipe P2 that connect the first heat exchanger 74 and the cascade heat exchanger 35. The first heat exchanger 74 exchanges heat between the heat medium circulating through the first circuit 5a and a heat source. The heat source functions as a hot or cold heat source for the heat medium circulating through the first circuit 5a. The heat source here is outdoor air that exchanges heat with the first refrigerant as the heat medium.

[0027] The second circuit 10 has a liquid pipe P3 and gas pipes P4, P5 which connect the second heat exchangers 52a, 52b, 52c and the cascade heat exchanger 35. In this embodiment, there is one liquid pipe P3 and two gas pipes P4, P5.

[0028] The refrigeration system 1 includes a first unit 5, a cascade unit 2, and second units 4a, 4b, and 4c. The first unit 5 includes a first heat exchanger 74. The second units 4a, 4b, and 4c include second heat exchangers 52a, 52b, and 52c. In this embodiment, the second units 4a, 4b, and 4c include branch units 6a, 6b, and 6c, and utilization units 3a, 3b, and 3c.

[0029] The refrigeration system 1 is configured by connecting a first unit 5, a cascade unit 2, and second units 4a, 4b, and 4c to each other via piping. The first unit 5 and the cascade unit 2 are connected by a first connecting piping 112 and a second connecting piping 111. The cascade unit 2 and the plurality of branch units 6a, 6b, and 6c are connected by three connecting pipings, namely, a third connecting piping 7, a fourth connecting piping 8, and a fifth connecting piping 9. The plurality of branch units 6a, 6b, and 6c are connected to the plurality of utilization units 3a, 3b, and 3c by first connecting piping 15a, 15b, and 15c and second connecting piping 16a, 16b, and 16c.

[0030] In this embodiment, the number of the first unit 5 is one. In this embodiment, the number of the cascade unit 2 is one. In this embodiment, the number of the second units 4a, 4b, 4c is three. In detail, the multiple usage units 3a, 3b, 3c of the second units 4a, 4b, 4c are three units, namely, the first usage unit 3a, the second usage unit 3b, and the third usage unit 3c. The multiple branching units 6a, 6b, 6c of the second units 4a, 4b, 4c are three units, namely, the first branching unit 6a, the second branching unit 6b, and the third branching unit 6c.

[0031] In the refrigeration system 1, each of the utilization units 3a, 3b, and 3c can individually perform cooling or heating operation, and is configured to enable heat recovery between the utilization units by sending refrigerant from the utilization unit performing heating operation to the utilization unit performing cooling operation. Specifically, in this embodiment, heat recovery is performed by performing cooling-dominated operation or heating-dominated operation in which cooling operation and heating operation are performed simultaneously. In addition, the refrigeration system 1 is configured to balance the heat load of the cascade unit 2 according to the overall heat load of the multiple utilization units 3a, 3b, and 3c taking into consideration the above-mentioned heat recovery (cooling-dominated operation or heating-dominated operation).

[0032] (2) First circuit The first circuit 5a includes a first compressor 71, a first switching mechanism 72, a first heat exchanger 74, a first expansion valve 76, a first subcooling heat exchanger 103, a first subcooling circuit 104, a first subcooling expansion valve 104a, a second stop valve 108, a second expansion valve 102, a cascade heat exchanger 35 shared with the second circuit 10, a first stop valve 109, a first accumulator 105, a first pipe P1, and a second pipe P2. The first circuit 5a also includes a first flow path 35b of the cascade heat exchanger 35.

[0033] The first pipe P1 is a pipe extending from the gas side of the first flow path 35b of the cascade heat exchanger 35 to the first heat exchanger 74. Here, the first pipe P1 is a gas pipe. The gas pipe is a pipe through which a refrigerant in a gas state or a two-phase gas-liquid state flows. The first pipe P1 includes a first connection pipe 112, a first refrigerant pipe 113 between the first connection pipe 112 and the cascade heat exchanger 35, and a pipe within the first unit 5.

[0034] The second pipe P2 is a pipe extending from the liquid side of the first flow path 35b of the cascade heat exchanger 35 to the first heat exchanger 74. Here, the second pipe P2 is a liquid pipe. The liquid pipe is a pipe through which a refrigerant in a liquid state, a gas-liquid two-phase state, or a supercritical state flows. The second pipe P2 includes the second connection pipe 111, the second refrigerant pipe 114 between the second connection pipe 111 and the cascade heat exchanger 35, and a pipe within the first unit 5.

[0035] The first circuit 5a has a first connection part C1 (see FIG. 9) for connecting the first pipe P1 and the second pipe P2 extending from the cascade heat exchanger 35, among the first pipe P1 and the second pipe P2 connecting the first heat exchanger 74 and the cascade heat exchanger 35, to the first pipe P1 and the second pipe P2 extending from the first heat exchanger 74 inside or outside the cascade casing 2x. Here, the first circuit 5a has first connection parts C11, C12 for connecting the first refrigerant pipe 113 and the second refrigerant pipe 114 extending from the cascade heat exchanger 35, among the first pipe P1 and the second pipe P2 connecting the first heat exchanger 74 and the cascade heat exchanger 35, to the first connection pipe 112 and the second connection pipe 111 inside or outside the cascade casing 2x.

[0036] The first compressor 71 is a device for compressing the first refrigerant, and is, for example, a positive displacement compressor such as a scroll type compressor whose operating capacity can be varied by inverter controlling a compressor motor 71a.

[0037] The first accumulator 105 is provided in the middle of the intake passage that connects the first switching mechanism 72 and the intake side of the first compressor 71.

[0038] When the cascade heat exchanger 35 functions as an evaporator of the first refrigerant, the first switching mechanism 72 is in a fifth connection state connecting the suction side of the first compressor 71 and the gas side of the first flow path 35b of the cascade heat exchanger 35 (see the solid line of the first switching mechanism 72 in FIG. 1). When the cascade heat exchanger 35 functions as a radiator of the first refrigerant, the first switching mechanism 72 is in a sixth connection state connecting the discharge side of the first compressor 71 and the gas side of the first flow path 35b of the cascade heat exchanger 35 (see the dashed line of the first switching mechanism 72 in FIG. 1). In this way, the first switching mechanism 72 is a device capable of switching the flow path of the refrigerant in the first circuit 5a, and is, for example, a four-way switching valve. By changing the switching state of the first switching mechanism 72, the cascade heat exchanger 35 can function as an evaporator or a radiator of the first refrigerant.

[0039] The cascade heat exchanger 35 is a device for performing heat exchange between a first refrigerant such as R32 and a second refrigerant such as carbon dioxide without mixing them. The cascade heat exchanger 35 is, for example, a plate-type heat exchanger. The cascade heat exchanger 35 has a second flow path 35a belonging to the second circuit 10 and a first flow path 35b belonging to the first circuit 5a. The gas side of the second flow path 35a is connected to the second switching mechanism 22 via the third heat source piping 25, and the liquid side is connected to the heat source side expansion valve 36 via the fourth heat source piping 26. The first flow path 35b has its gas side connected to the first compressor 71 via the first piping P1 (more specifically, the first refrigerant piping 113, the first connecting piping 112, the first shut-off valve 109, and the first switching mechanism 72), and its liquid side connected to the second piping P2 (more specifically, the second refrigerant piping 114 in which the second expansion valve 102 is provided).

[0040] The first heat exchanger 74 is a device for exchanging heat between the first refrigerant and the outdoor air. In the first heat exchanger 74, the first refrigerant obtains cold or hot heat from the outdoor air. The gas side of the first heat exchanger 74 is connected to the first pipe P1 extending from the first switching mechanism 72. The first heat exchanger 74 is, for example, a fin-and-tube type heat exchanger configured with a large number of heat transfer tubes and fins.

[0041] The first expansion valve 76 is provided in the second pipe P2 extending from the liquid side of the first heat exchanger 74 to the first subcooling heat exchanger 103. The first expansion valve 76 is an electrically operated expansion valve with adjustable opening that adjusts the flow rate of the first refrigerant flowing through the liquid side of the first circuit 5a.

[0042] The first subcooling circuit 104 branches off between the first expansion valve 76 and the first subcooling heat exchanger 103, and is connected to a portion of the suction flow path between the first switching mechanism 72 and the first accumulator 105. The first subcooling expansion valve 104a is provided upstream of the first subcooling heat exchanger 103 in the first subcooling circuit 104, and is an electrically operated expansion valve with adjustable opening that adjusts the flow rate of the first refrigerant, etc.

[0043] The first subcooling heat exchanger 103 is a heat exchanger that exchanges heat between the refrigerant flowing from the first expansion valve 76 toward the second shutoff valve 108 and the refrigerant whose pressure has been reduced in the first subcooling expansion valve 104a in the first subcooling circuit 104.

[0044] The first connection pipe 112 is a pipe that connects the first unit 5 and the cascade unit 2. The second connection pipe 111 is a pipe that connects the first unit 5 and the cascade unit 2.

[0045] The second expansion valve 102 is provided in the second refrigerant pipe 114. The second expansion valve 102 is an electric expansion valve whose opening degree can be adjusted to adjust the flow rate of the first refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35.

[0046] The first shutoff valve 109 is provided between the first connection pipe 112 and the first switching mechanism 72 .

[0047] The second stop valve 108 is provided between the second connection pipe 111 and the first subcooling heat exchanger 103 .

[0048] (3)Second circuit (3-1) Overview of the Second Circuit The second circuit 10 is configured by connecting a plurality of utilization units 3a, 3b, 3c, a plurality of branch units 6a, 6b, 6c, and a cascade unit 2 to each other. Each utilization unit 3a, 3b, 3c is connected to a corresponding branch unit 6a, 6b, 6c in a one-to-one relationship. Specifically, the utilization unit 3a and the branch unit 6a are connected via a first connection pipe 15a and a second connection pipe 16a, the utilization unit 3b and the branch unit 6b are connected via a first connection pipe 15b and a second connection pipe 16b, and the utilization unit 3c and the branch unit 6c are connected via a first connection pipe 15c and a second connection pipe 16c. In addition, each branch unit 6a, 6b, 6c is connected to the cascade unit 2 via three connection pipes, that is, a third connection pipe 7, a fourth connection pipe 8, and a fifth connection pipe 9. Specifically, a third connection pipe 7, a fourth connection pipe 8, and a fifth connection pipe 9 extending from the cascade unit 2 each branch into a plurality of pipes, which are connected to the respective branch units 6a, 6b, and 6c.

[0049] Depending on the operating state, either a gas-liquid two-phase refrigerant or a liquid refrigerant flows through the third connecting pipe 7. Depending on the type of the second refrigerant, either a supercritical refrigerant flows through the third connecting pipe 7. Depending on the operating state, either a gas-liquid two-phase refrigerant or a gaseous refrigerant flows through the fourth connecting pipe 8. Depending on the type of the second refrigerant, either a supercritical refrigerant flows through the fourth connecting pipe 8. Depending on the operating state, either a gas-liquid two-phase refrigerant or a gaseous refrigerant flows through the fifth connecting pipe 9.

[0050] The second circuit 10 is configured by connecting a heat source circuit 12, branch circuits 14a, 14b, and 14c, and utilization circuits 13a, 13b, and 13c to each other.

[0051] (3-2) Heat source circuit The heat source circuit 12 mainly includes the second compressor 21, the second switching mechanism 22, the first heat source pipe 28, the second heat source pipe 29, the intake passage 23, the discharge passage 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, the third shutoff valve 32, the fourth shutoff valve 33, the fifth shutoff valve 31, the second accumulator 30, the oil separator 34, the oil return circuit 40, the second receiver 45, the bypass circuit 46, the bypass expansion valve 46a, the second supercooling heat exchanger 47, the second supercooling circuit 48, and the second supercooling expansion valve 48a. The heat source circuit 12 of the second circuit 10 also includes the second flow passage 35a of the cascade heat exchanger 35.

[0052] The second compressor 21 is a device for compressing the second refrigerant in the heat source circuit 12 of the second circuit, and is, for example, a scroll type or other positive displacement compressor whose operating capacity can be varied by inverter controlling the compressor motor 21a. The second compressor 21 is controlled according to the load during operation so that the operating capacity increases as the load increases.

[0053] The second switching mechanism 22 is a mechanism capable of switching the connection state of the second circuit 10, in particular, the flow path of the refrigerant in the heat source circuit 12. In this embodiment, the second switching mechanism 22 has a discharge side communication part 22x, a suction side communication part 22y, a first switching valve 22a, and a second switching valve 22b. The discharge side communication part 22x is connected to an end of the discharge flow path 24 opposite to the second compressor 21 side. The suction side communication part 22y is connected to an end of the suction flow path 23 opposite to the second compressor 21 side. The first switching valve 22a and the second switching valve 22b are provided in parallel with each other between the discharge flow path 24 and the suction flow path 23 of the second compressor 21. The first switching valve 22a is connected to one end of the discharge side communication part 22x and one end of the suction side communication part 22y. The second switching valve 22b is connected to the other end of the discharge side communication part 22x and the other end of the suction side communication part 22y. In this embodiment, the first switching valve 22a and the second switching valve 22b are both configured as four-way switching valves. The first switching valve 22a and the second switching valve 22b each have four connection ports, namely, a first connection port, a second connection port, a third connection port, and a fourth connection port. In the first switching valve 22a and the second switching valve 22b of this embodiment, each of the fourth ports is closed and is a connection port that is not connected to the flow path of the second circuit 10. The first switching valve 22a has a first connection port connected to one end of the discharge side communication part 22x, a second connection port connected to the third heat source pipe 25 extending from the second flow path 35a of the cascade heat exchanger 35, and a third connection port connected to one end of the suction side communication part 22y. The first switching valve 22a switches between a switching state in which the first connection port and the second connection port are connected and the third connection port and the fourth connection port are connected, and a switching state in which the third connection port and the second connection port are connected and the first connection port and the fourth connection port are connected. The second switching valve 22b has a first connection port connected to the other end of the discharge side communication section 22x, a second connection port connected to the first heat source pipe 28, and a third connection port connected to the other end of the suction side communication section 22y. The second switching valve 22b switches between a switching state in which the first connection port and the second connection port are connected and the third connection port and the fourth connection port are connected, and a switching state in which the third connection port and the second connection port are connected and the first connection port and the fourth connection port are connected.

[0054] When the second switching mechanism 22 is to suppress the second refrigerant discharged from the second compressor 21 from being sent to the fourth connection pipe 8 while causing the cascade heat exchanger 35 to function as a radiator of the second refrigerant, the second switching mechanism 22 is switched to a first connection state in which the discharge passage 24 and the third heat source pipe 25 are connected by the first switching valve 22a and the first heat source pipe 28 and the suction passage 23 are connected by the second switching valve 22b. The first connection state of the second switching mechanism 22 is a connection state adopted during cooling operation, which will be described later. When the cascade heat exchanger 35 is to function as an evaporator of the second refrigerant, the second switching mechanism 22 is switched to a second connection state in which the discharge passage 24 and the first heat source pipe 28 are connected by the second switching valve 22b and the third heat source pipe 25 and the suction passage 23 are connected by the first switching valve 22a. The second connection state of the second switching mechanism 22 is a connection state adopted during heating operation and heating-dominated operation described later. When the second refrigerant discharged from the second compressor 21 is sent to the fourth connection pipe 8 while the cascade heat exchanger 35 functions as a radiator of the second refrigerant, the second switching mechanism 22 is switched to a third connection state in which the discharge flow path 24 and the third heat source pipe 25 are connected by the first switching valve 22a and the discharge flow path 24 and the first heat source pipe 28 are connected by the second switching valve 22b. The third connection state of the second switching mechanism 22 is a connection state adopted during cooling-dominated operation described later.

[0055] As described above, the cascade heat exchanger 35 is a device for performing heat exchange between a first refrigerant, such as R32, flowing through the first circuit 5a and a second refrigerant, such as carbon dioxide, flowing through the second circuit 10, without mixing them. The cascade heat exchanger 35 is shared by the first unit 5 and the cascade unit 2 by having a second flow path 35a through which the second refrigerant of the second circuit 10 flows and a first flow path 35b through which the first refrigerant of the first circuit 5a flows. In this embodiment, the cascade heat exchanger 35 is disposed inside the cascade casing 2x of the cascade unit 2, as shown in FIG. 7. The gas side of the first flow path 35b of the cascade heat exchanger 35 extends through the first refrigerant piping 113 to the first connection piping 112 outside the cascade casing 2x. The liquid side of the first flow path 35b of the cascade heat exchanger 35 passes through a second refrigerant pipe 114 in which a second expansion valve 102 is provided, and extends to a second connection pipe 111 outside the cascade casing 2x.

[0056] The heat source side expansion valve 36 is an electrically operated expansion valve whose opening degree can be adjusted and is connected to the liquid side of the cascade heat exchanger 35 in order to adjust the flow rate of the second refrigerant flowing through the cascade heat exchanger 35. The heat source side expansion valve 36 is provided in the fourth heat source piping 26.

[0057] The third shutoff valve 32, the fourth shutoff valve 33, and the fifth shutoff valve 31 are valves provided at connection ports to external equipment and piping (specifically, the connecting piping 7, 8, and 9). Specifically, the third shutoff valve 32 is connected to the fourth connecting piping 8 drawn from the cascade unit 2. The fourth shutoff valve 33 is connected to the fifth connecting piping 9 drawn from the cascade unit 2. The fifth shutoff valve 31 is connected to the third connecting piping 7 drawn from the cascade unit 2.

[0058] The first heat source piping 28 is a refrigerant piping that connects the third shutoff valve 32 and the second switching mechanism 22. Specifically, the first heat source piping 28 connects the third shutoff valve 32 and the second connection port of the second switching valve 22b of the second switching mechanism 22.

[0059] The suction passage 23 is a passage that communicates between the second switching mechanism 22 and the suction side of the second compressor 21. Specifically, the suction passage 23 connects the suction side communication unit 22y of the second switching mechanism 22 and the suction side of the second compressor 21. A second accumulator 30 is provided in the middle of the suction passage 23.

[0060] The second heat source piping 29 is a refrigerant piping that connects the fourth shutoff valve 33 and a portion of the suction passage 23. In this embodiment, the second heat source piping 29 is connected to the suction passage 23 at a connection point between the suction side communication part 22y of the second switching mechanism 22 and the second accumulator 30.

[0061] The discharge flow path 24 is a refrigerant piping that connects the discharge side of the second compressor 21 and the second switching mechanism 22. Specifically, the discharge flow path 24 connects the discharge side of the second compressor 21 and a discharge side communication unit 22x of the second switching mechanism 22.

[0062] The third heat source piping 25 is a refrigerant piping that connects the second switching mechanism 22 and the gas side of the cascade heat exchanger 35. Specifically, the third heat source piping 25 connects the second connection port of the first switching valve 22a of the second switching mechanism 22 and the gas side end of the second flow path 35a in the cascade heat exchanger 35.

[0063] The fourth heat source piping 26 is a refrigerant piping that connects the liquid side (the side opposite to the gas side, the side opposite to the side where the second switching mechanism 22 is provided) of the cascade heat exchanger 35 and the second receiver 45. Specifically, the fourth heat source piping 26 connects the liquid side end (the end opposite to the gas side) of the second flow path 35a in the cascade heat exchanger 35 and the second receiver 45.

[0064] The second receiver 45 is a refrigerant container that stores excess refrigerant in the second circuit 10. From the second receiver 45, a fourth heat source pipe 26, a fifth heat source pipe 27, and a bypass circuit 46 extend.

[0065] The bypass circuit 46 is a refrigerant pipe that connects a gas phase region, which is an upper region inside the second receiver 45, with the suction passage 23. Specifically, the bypass circuit 46 is connected to a portion of the suction passage 23 between the second switching mechanism 22 and the second accumulator 30. The bypass circuit 46 is provided with a bypass expansion valve 46a. The bypass expansion valve 46a is an electric expansion valve that can adjust the amount of refrigerant guided from inside the second receiver 45 to the suction side of the second compressor 21 by adjusting the opening degree.

[0066] The fifth heat source pipe 27 is a refrigerant pipe that connects the second receiver 45 and the fifth stop valve 31.

[0067] The second subcooling circuit 48 is a refrigerant pipe that connects a part of the fifth heat source pipe 27 and the suction passage 23. Specifically, the second subcooling circuit 48 is connected to a portion of the suction passage 23 between the second switching mechanism 22 and the second accumulator 30. In this embodiment, the second subcooling circuit 48 extends so as to branch off from between the second receiver 45 and the second subcooling heat exchanger 47.

[0068] The second subcooling heat exchanger 47 is a heat exchanger that performs heat exchange between the refrigerant flowing through a flow path belonging to the fifth heat source pipe 27 and the refrigerant flowing through a flow path belonging to the second subcooling circuit 48. In this embodiment, the second subcooling heat exchanger 47 is provided between a point in the fifth heat source pipe 27 where the second subcooling circuit 48 branches off and the fifth stop valve 31. The second subcooling expansion valve 48a is provided between a branching point from the fifth heat source pipe 27 in the second subcooling circuit 48 and the second subcooling heat exchanger 47. The second subcooling expansion valve 48a supplies the decompressed refrigerant to the second subcooling heat exchanger 47, and is an electrically-operated expansion valve whose opening degree is adjustable.

[0069] The second accumulator 30 is a container capable of storing the second refrigerant, and is provided on the suction side of the second compressor 21.

[0070] The oil separator 34 is provided in the middle of the discharge flow path 24. The oil separator 34 is a device for separating the refrigeration oil discharged from the second compressor 21 together with the second refrigerant from the second refrigerant, and returning the refrigeration oil to the second compressor 21.

[0071] The oil return circuit 40 is provided to connect the oil separator 34 and the suction passage 23. The oil return circuit 40 has an oil return passage 41 extending from the oil separator 34 so as to join a portion of the suction passage 23 between the second accumulator 30 and the suction side of the second compressor 21. An oil return on-off valve 44 is provided in the middle of the oil return passage 41. By controlling the oil return on-off valve 44 to an open state, the refrigeration oil separated in the oil separator 34 passes through the oil return passage 41 and is returned to the suction side of the second compressor 21. Here, in this embodiment, when the second compressor 21 is in an operating state in the second circuit 10, the oil return on-off valve 44 repeatedly maintains an open state for a predetermined time and a closed state for a predetermined time, thereby controlling the amount of refrigeration oil returned through the oil return circuit 40. Note that, in this embodiment, the oil return on-off valve 44 is an electromagnetic valve that is controlled to open and close, but it may be an electric expansion valve whose opening degree can be adjusted.

[0072] (3-3)Used circuit The utilization circuits 13a, 13b, and 13c will be described below. However, since the utilization circuits 13b and 13c have the same configuration as the utilization circuit 13a, the suffix "b" or "c" will be added to the symbols indicating each part of the utilization circuit 13a instead of the suffix "a" for the utilization circuits 13b and 13c, and the description of each part will be omitted.

[0073] The utilization circuit 13a mainly includes a second heat exchanger 52a, a first utilization pipe 57a, a second utilization pipe 56a, and a utilization side expansion valve 51a.

[0074] The second heat exchanger 52a is a device for exchanging heat between the refrigerant and the indoor air, and is, for example, a fin-and-tube type heat exchanger composed of a number of heat transfer tubes and fins. The second heat exchangers 52a, 52b, and 52c are connected in parallel to the second switching mechanism 22, the intake passage 23, and the cascade heat exchanger 35.

[0075] One end of the second utilization pipe 56a is connected to the liquid side (opposite the gas side) of the second heat exchanger 52a of the first utilization unit 3a. The other end of the second utilization pipe 56a is connected to the second connection pipe 16a. The utilization side expansion valve 51a described above is provided midway along the second utilization pipe 56a.

[0076] The utilization side expansion valve 51a is an electrically operated expansion valve capable of adjusting the opening degree and adjusting the flow rate of the refrigerant flowing through the second heat exchanger 52a, etc. The utilization side expansion valve 51a is provided in the second utilization pipe 56a.

[0077] One end of the first utilization pipe 57a is connected to the gas side of the second heat exchanger 52a of the first utilization unit 3a. In this embodiment, the first utilization pipe 57a is connected to the side opposite to the utilization side expansion valve 51a of the second heat exchanger 52a. The other end of the first utilization pipe 57a is connected to the first connection pipe 15a.

[0078] (3-4) Branch circuit The branch circuits 14a, 14b, and 14c will be described below. However, since the branch circuits 14b and 14c have the same configuration as the branch circuit 14a, the explanation of each part of the branch circuits 14b and 14c will be omitted by adding the suffix "b" or "c" instead of the suffix "a" to the symbols indicating each part of the branch circuit 14a.

[0079] The branch circuit 14a mainly includes a junction pipe 62a, a first branch pipe 63a, a second branch pipe 64a, a first control valve 66a, a second control valve 67a, a bypass pipe 69a, a check valve 68a, and a third branch pipe 61a.

[0080] One end of the junction pipe 62a is connected to the first connection pipe 15a. A first branch pipe 63a and a second branch pipe 64a are branched and connected to the other end of the junction pipe 62a.

[0081] The first branch pipe 63a is connected to the fourth connection pipe 8 at the side opposite to the junction pipe 62. The first branch pipe 63a is provided with a first control valve 66a that can be opened and closed.

[0082] The second branch pipe 64a is connected to the fifth connection pipe 9 at the opposite end to the junction pipe 62. The second branch pipe 64a is provided with a second control valve 67a that can be opened and closed.

[0083] The bypass pipe 69a is a refrigerant pipe that connects a portion of the first branch pipe 63a that is closer to the fourth connection pipe 8 than the first control valve 66a and a portion of the second branch pipe 64a that is closer to the fifth connection pipe 9 than the second control valve 67a. A check valve 68a is provided in the middle of the bypass pipe 69a. The check valve 68a only allows refrigerant to flow from the second branch pipe 64a side to the first branch pipe 63a side, and does not allow refrigerant to flow from the first branch pipe 63a side to the second branch pipe 64a side.

[0084] The third branch pipe 61a has one end connected to the second connection pipe 16a and the other end connected to the third connection pipe 7.

[0085] When performing the cooling operation described later, the first branch unit 6a can function as follows by closing the first control valve 66a and opening the second control valve 67a. The first branch unit 6a sends the refrigerant flowing into the third branch pipe 61a through the third connection pipe 7 to the second connection pipe 16a. The refrigerant flowing through the second usage pipe 56a of the first usage unit 3a through the second connection pipe 16a is sent to the second heat exchanger 52a of the first usage unit 3a through the usage side expansion valve 51a. The refrigerant sent to the second heat exchanger 52a is evaporated by heat exchange with the indoor air, and then flows through the first connection pipe 15a via the first usage pipe 57a. The refrigerant that has flowed through the first connection pipe 15a is sent to the junction pipe 62a of the first branch unit 6a. The refrigerant that has flowed through the junction pipe 62a does not flow to the first branch pipe 63a side, but flows to the second branch pipe 64a side. The refrigerant flowing through the second branch pipe 64a passes through the second control valve 67a. A portion of the refrigerant that has passed through the second control valve 67a is sent to the fifth connection pipe 9. The remaining portion of the refrigerant that has passed through the second control valve 67a flows so as to branch off into a bypass pipe 69a provided with a check valve 68a, passes through a portion of the first branch pipe 63a, and is then sent to the fourth connection pipe 8. This makes it possible to increase the total flow path cross-sectional area when sending the second refrigerant in a gaseous state evaporated in the second heat exchanger 52a to the second compressor 21, thereby reducing pressure loss.

[0086] In addition, when performing cooling-dominated operation and heating-dominated operation described later, the first branch unit 6a can function as follows when cooling the room in the first usage unit 3a by closing the first control valve 66a and opening the second control valve 67a. The first branch unit 6a sends the refrigerant flowing into the third branch pipe 61a through the third connection pipe 7 to the second connection pipe 16a. The refrigerant flowing through the second usage pipe 56a of the first usage unit 3a through the second connection pipe 16a is sent to the second heat exchanger 52a of the first usage unit 3a through the usage-side expansion valve 51a. The refrigerant sent to the second heat exchanger 52a is evaporated by heat exchange with the indoor air, and then flows through the first connection pipe 15a via the first usage pipe 57a. The refrigerant that has flowed through the first connection pipe 15a is sent to the junction pipe 62a of the first branch unit 6a. The refrigerant that has flowed through the junction pipe 62a flows into the second branch pipe 64a and passes through the second control valve 67a, and is then sent to the fifth connection pipe 9.

[0087] In addition, when performing a heating operation described later, the first branch unit 6a can function as follows by closing the second control valve 67a and opening the first control valve 66a. In the first branch unit 6a, the refrigerant flowing into the first branch pipe 63a through the fourth connection pipe 8 passes through the first control valve 66a and is sent to the junction pipe 62a. The refrigerant that has flowed through the junction pipe 62a passes through the first use pipe 57a of the use unit 3a via the first connection pipe 15a and is sent to the second heat exchanger 52a. The refrigerant sent to the second heat exchanger 52a dissipates heat by heat exchange with the indoor air, and then passes through the use-side expansion valve 51a provided in the second use pipe 56a. The refrigerant that has passed through the second use pipe 56a passes through the third branch pipe 61a of the first branch unit 6a via the second connection pipe 16a, and is then sent to the third connection pipe 7.

[0088] In addition, when performing cooling-dominated operation and heating-dominated operation described later, the first branch unit 6a can function as follows when heating the room in the first utilization unit 3a by closing the second control valve 67a and opening the first control valve 66a. In the first branch unit 6a, the refrigerant flowing into the first branch pipe 63a through the fourth connection pipe 8 passes through the first control valve 66a and is sent to the junction pipe 62a. The refrigerant that has flowed through the junction pipe 62a passes through the first utilization pipe 57a of the utilization unit 3a via the first connection pipe 15a and is sent to the second heat exchanger 52a. The refrigerant sent to the second heat exchanger 52a dissipates heat by heat exchange with the indoor air, and then passes through the utilization-side expansion valve 51a provided in the second utilization pipe 56a. The refrigerant that has passed through the second utilization pipe 56a passes through the second connection pipe 16a, flows through the third branch pipe 61a of the first branch unit 6a, and is then sent to the third connection pipe 7.

[0089] Such a function is possessed not only by the first branch unit 6a but also by the second branch unit 6b and the third branch unit 6c. Therefore, the first branch unit 6a, the second branch unit 6b, and the third branch unit 6c are capable of individually switching whether to function as a refrigerant evaporator or a refrigerant radiator for each of the second heat exchangers 52a, 52b, and 52c.

[0090] (3-5) Liquid and gas pipes As described above, the second circuit 10 has the liquid pipe P3 and the gas pipes P4 and P5 that connect the second heat exchangers 52a, 52b, 52c to the cascade heat exchanger 35. The gas pipes in this embodiment are the first gas pipe P4 and the second gas pipe P5.

[0091] The liquid pipe P3 is a pipe extending from the liquid side of the second flow path 35a of the cascade heat exchanger 35 to the second heat exchangers 52a, 52b, and 52c. The liquid pipe is a pipe through which a refrigerant in a liquid state, a gas-liquid two-phase state, or a supercritical state flows.

[0092] The liquid pipe P3 in this embodiment is connected to the fifth shutoff valve 31. In detail, the liquid pipe P3 includes the third connection pipe 7, the fourth heat source pipe 26, the fifth heat source pipe 27, the second connection pipes 16a, 16b, 16c, the second utilization pipes 56a, 56b, 56c, and the third branch pipes 61a, 61b, 61c.

[0093] The gas pipes P4 and P5 extend from the gas side of the second flow passage 35a of the cascade heat exchanger 35 to the second heat exchangers 52a, 52b, and 52c. The gas pipes P4 and P5 are pipes through which a refrigerant in a gas state or a two-phase gas-liquid state flows.

[0094] The first gas pipe P4 in this embodiment is connected to the third shutoff valve 32. In detail, the first gas pipe P4 includes the fourth connection pipe 8, the third heat source pipe 25, the first heat source pipe 28, the intake passage 23, the discharge passage 24, the first connection pipes 15a, 15b, and 15c, the first utilization pipes 57a, 57b, and 57c, the junction pipes 62a, 62b, and 62c, the first branch pipes 63a, 63b, and 63c, and the bypass pipes 69a, 69b, and 69c.

[0095] The second gas pipe P5 in this embodiment is connected to the fourth stop valve 33. In detail, the second gas pipe P5 includes the fifth connection pipe 9, the third heat source pipe 25, the second heat source pipe 29, the discharge flow path 24, the first connection pipes 15a, 15b, and 15c, the first utilization pipes 57a, 57b, and 57c, the junction pipes 62a, 62b, and 62c, and the second branch pipes 64a, 64b, and 64c.

[0096] The second circuit 10 has a second connection part C2 (see Figure 9) for connecting the liquid pipe P3 and the gas pipe P4 extending from the cascade heat exchanger 35, among the liquid pipe P3 and the gas pipe P4 connecting the second heat exchanger 52a, 52b, 52c and the cascade heat exchanger 35, to the liquid pipe P3 and the gas pipe P4 extending from the second heat exchanger 52a, 52b, 52c inside or outside the cascade casing 2x.

[0097] The second circuit 10 has a second connection part C2 (see FIG. 9) for connecting the liquid pipe P3 and the gas pipes P4, P5 extending from the second heat exchangers 52a, 52b, 52c inside or outside the cascade casing 2x (see FIGS. 7 and 8). Here, the second circuit 10 has a second connection part C21 for connecting the liquid pipe P3, a second connection part C22 for connecting the first gas pipe P4, and a second connection part C23 for connecting the second gas pipe P5.

[0098] (4) Unit 1 The first unit 5 is disposed in a space different from the space in which the second units 4a, 4b, and 4c (specifically, the utilization units 3a, 3b, and 3c and the branching units 6a, 6b, and 6c) are disposed. Here, the first unit 5 is disposed on the rooftop of a building.

[0099] The first unit 5 has a part of the above-mentioned first circuit 5a, a first fan 75, various sensors, a first control unit 70, and a first casing 5x as shown in FIG.

[0100] The first unit 5 includes, as a part of the first circuit 5a, a first compressor 71, a first switching mechanism 72, a first heat exchanger 74, a first expansion valve 76, a first subcooling heat exchanger 103, a first subcooling circuit 104, a first subcooling expansion valve 104a, a second stop valve 108, a first stop valve 109, a first accumulator 105, a part of the first pipe P1, and a part of the second pipe P2. The first unit 5 further includes a first casing 5x shown in FIG.

[0101] The first casing 5x is a rectangular parallelepiped having multiple faces. The first casing 5x accommodates the first compressor 71, the first switching mechanism 72, the first heat exchanger 74, the first expansion valve 76, the first subcooling heat exchanger 103, the first subcooling circuit 104, the first subcooling expansion valve 104a, the second shutoff valve 108, the first shutoff valve 109, and the first accumulator 105. The first casing 5x also accommodates a part of the first pipe P1 and a part of the second pipe P2. A first connecting pipe 112 constituting the first pipe P1 and a second connecting pipe 111 constituting the second pipe P2 extend from the first casing 5x.

[0102] The first fan 75 is provided in the first unit 5, and generates an air flow in which the outdoor air is guided to the first heat exchanger 74, where it exchanges heat with the first refrigerant flowing through the first heat exchanger 74, and then the air is discharged to the outside. The first fan 75 is driven by a first fan motor 75a.

[0103] In addition, various sensors are provided in the first unit 5. Specifically, an outside air temperature sensor 77 that detects the temperature of the outside air before passing through the first heat exchanger 74, a first discharge pressure sensor 78 that detects the pressure of the first refrigerant discharged from the first compressor 71, a first suction pressure sensor 79 that detects the pressure of the first refrigerant sucked into the first compressor 71, a first suction temperature sensor 81 that detects the temperature of the first refrigerant sucked into the first compressor 71, and a first heat exchange temperature sensor 82 that detects the temperature of the refrigerant flowing through the first heat exchanger 74 are provided.

[0104] The first control unit 70 controls the operation of each of the members 71 (71a), 72, 75 (75a), 76, and 104a provided in the first unit 5. The first control unit 70 has a processor, such as a CPU or a microcomputer, and a memory provided for controlling the first unit 5, and is capable of exchanging control signals and the like with a remote control (not shown), as well as with the heat source side control unit 20 of the cascade unit 2, the branching unit control units 60a, 60b, and 60c, and the utilization side control units 50a, 50b, and 50c.

[0105] (5) Cascade unit (5-1) Overview The cascade unit 2 is arranged in a space different from the space in which the second units 4a, 4b, and 4c (specifically, the utilization units 3a, 3b, and 3c and the branching units 6a, 6b, and 6c) are arranged. Here, the cascade unit 2 is arranged on the rooftop of a building.

[0106] The cascade unit 2 is connected to the branch units 6a, 6b, and 6c via connecting pipes 7, 8, and 9, and constitutes a part of the second circuit 10. In addition, the cascade unit 2 is connected to the first unit 5 via connecting pipes 111 and 112, and constitutes a part of the first circuit 5a.

[0107] The cascade unit 2 includes the above-mentioned heat source circuit 12, various sensors, a heat source side control unit 20, a portion of the first piping P1 and a portion of the second piping P2 constituting the first circuit 5a, a cascade casing 2x as shown in Figures 7 and 8, electrical equipment 90 shown in Figure 8, and wiring.

[0108] The electrical equipment 90 drives the second compressor 21. The wiring is connected to the electrical equipment 90. Here, the wiring is an electric wiring and includes a signal line.

[0109] The cascade unit 2 includes a second suction pressure sensor 37 that detects the pressure of the second refrigerant on the suction side of the second compressor 21, a second discharge pressure sensor 38 that detects the pressure of the second refrigerant on the discharge side of the second compressor 21, a second discharge temperature sensor 39 that detects the temperature of the second refrigerant on the discharge side of the second compressor 21, a second suction temperature sensor 88 that detects the temperature of the second refrigerant on the suction side of the second compressor 21, and a cascade temperature sensor 83 that detects the temperature of the second refrigerant flowing between the second flow path 35a of the cascade heat exchanger 35 and the heat source side expansion valve 36. There are also provided a receiver outlet temperature sensor 84 that detects the temperature of the second refrigerant flowing between the second receiver 45 and the second subcooling heat exchanger 47, a bypass circuit temperature sensor 85 that detects the temperature of the second refrigerant flowing downstream of the bypass expansion valve 46a in the bypass circuit 46, a subcooling outlet temperature sensor 86 that detects the temperature of the second refrigerant flowing between the second subcooling heat exchanger 47 and the fifth stop valve 31, and a subcooling circuit temperature sensor 87 that detects the temperature of the second refrigerant flowing at the outlet of the second subcooling heat exchanger 47 in the second subcooling circuit 48.

[0110] The heat source side control section 20 controls the operation of each of the members 21 (21a), 22, 36, 44, 46a, 48a, 102 provided inside the cascade casing 2x of the cascade unit 2. The heat source side control section 20 has a processor such as a CPU or a microcomputer and a memory provided for controlling the cascade unit 2, and is capable of exchanging control signals and the like with the first control section 70 of the first unit 5, the utilization side control sections 50a, 50b, 50c of the utilization units 3a, 3b, 3c, and the branching unit control sections 60a, 60b, 60c.

[0111] In this manner, the heat source side control unit 20 can control not only each component constituting the heat source circuit 12 of the second circuit 10, but also the second expansion valve 102 constituting a part of the first circuit 5a. Therefore, the heat source side control unit 20 can control the valve opening degree of the second expansion valve 102 itself based on the state of the heat source circuit 12 that it controls, thereby making it possible to bring the state of the heat source circuit 12 closer to a desired state. Specifically, it becomes possible to control the amount of heat that the second refrigerant flowing through the second flow path 35a of the cascade heat exchanger 35 in the heat source circuit 12 receives from the first refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35 or the amount of heat that the second refrigerant flowing through the second flow path 35a of the cascade heat exchanger 35 receives from the first refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35 or the amount of heat that the second refrigerant gives to the first refrigerant.

[0112] (5-2) Characteristic parts (5-2-1) Cascade casing The cascade casing 2x accommodates a part of the first circuit 5a and a part of the second circuit 10 shown in Fig. 9. In this embodiment, the part of the first circuit 5a includes the second refrigerant pipe 114 which is a part of the second pipe P2, the second expansion valve 102, the first flow path 35b of the cascade heat exchanger 35, and the first refrigerant pipe 113 which is a part of the first pipe P1. A part of the second circuit 10 includes the second compressor 21, the second switching mechanism 22, the first heat source pipe 28, the second heat source pipe 29, the intake passage 23, the discharge passage 24, the third heat source pipe 25, the fourth heat source pipe 26, the fifth heat source pipe 27, the second passage 35a of the cascade heat exchanger 35, the heat source side expansion valve 36, the fifth shutoff valve 31, the third shutoff valve 32, the fourth shutoff valve 33, the second accumulator 30, the oil separator 34, the oil return circuit 40, the second receiver 45, the bypass circuit 46, the bypass expansion valve 46a, the second supercooling heat exchanger 47, the second supercooling circuit 48, and the second supercooling expansion valve 48a. Furthermore, the cascade casing 2x accommodates an electrical component 90 and a plurality of wirings.

[0113] A third connection pipe 7, a fourth connection pipe 8, and a fifth connection pipe 9, which are parts of the second circuit 10, extend from the cascade casing 2x. In addition, a second connection pipe 111 and a first connection pipe 112, which are parts of the first circuit 5a, extend from the cascade casing 2x.

[0114] As shown in Fig. 8, the cascade casing 2x is a rectangular parallelepiped having a top surface 120e, a bottom surface 120f, and side surfaces. The top surface 120e and the bottom surface 120f face each other. The cascade casing 2x has four side surfaces, a front surface 120a, a rear surface 120b, a left surface 120c, and a right surface 120d. The front surface 120a and the rear surface 120b face each other. The left surface 120c and the right surface 120d face each other.

[0115] In this embodiment, the cascade casing 2x includes a front plate constituting the front surface 120a, a rear plate constituting the rear surface 120b, a left plate constituting the left surface 120c, a right plate constituting the right surface 120d, an upper plate constituting the upper surface 120e, and a bottom plate constituting the bottom surface 120f. The bottom plate has a rectangular shape.

[0116] The cascade heat exchanger 35 is disposed on a bottom plate constituting the bottom surface 120f. As shown in Fig. 10, when viewed from the front surface 120a, the electrical equipment 90 and the cascade heat exchanger 35 do not overlap. In other words, the cascade heat exchanger 35 and the electrical equipment 90 are disposed separately in the longitudinal direction (first direction) of the front surface 120a as a side surface.

[0117] As shown in FIG. 9, the first pipe P1 and the second pipe P2 are disposed near the bottom surface 120f.

[0118] The front surface 120a extends in a second direction extending vertically and a first direction intersecting the second direction. Here, the front surface 120a extends in the vertical direction as the second direction and in the left-right direction as the first direction perpendicular to the vertical direction. An opening O is formed in the front surface 120a. The opening O includes a piping opening O1 and a wiring opening O2.

[0119] The front surface 120a is composed of an upper plate 120a1, a lower plate 120a2, a first fixed plate 120a3, and a second fixed plate 120a4. The upper plate 120a1 and the lower plate 120a2 are removable plate members. The upper plate 120a1 covers an opening for maintenance. The lower plate 120a2 is disposed below the upper plate 120a1. The first fixed plate 120a3 and the second fixed plate 120a4 are plate members fixed to a bottom plate constituting the bottom surface 120f.

[0120] When the upper plate 120a1 and the lower plate 120a2 are removed, an opening for maintenance is exposed. In this embodiment, since the opening for maintenance is exposed on the front surface 120a side, maintenance can be performed from the front surface 120a side. In this case, a service space for performing maintenance is provided on the front surface 120a side. Here, since the piping port O1 and the wiring port O2 are formed on the front surface 120a, the service space is provided only on the front surface 120a side.

[0121] The first fixing plate 120a3 has a piping port O1. The piping port O1 is an opening for drawing out the first piping P1 and the second piping P2 of the first circuit 5a, and the liquid pipe P3 and the gas pipes P4 and P5 of the second circuit 10. Therefore, the first piping P1, the second piping P2, the liquid pipe P3, and the gas pipes P4 and P5 pass through the piping port O1. In detail, the piping port O1 is provided with the first refrigerant piping 113 or the first connecting piping 112, the second refrigerant piping 114 or the second connecting piping 111, the liquid refrigerant pipe extending from the third connecting piping 7 or the cascade heat exchanger 35, the fourth connecting piping 8 or the cascade heat exchanger 35, and the gas refrigerant pipe extending from the fifth connecting piping 9 or the cascade heat exchanger 35. The cascade heat exchanger 35 is disposed near the piping port O1.

[0122] The pipe opening O1 is a common opening where the first pipe P1 and the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are located. Here, at the pipe opening O1, the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are arranged in a plurality of different directions. In other words, the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are not arranged in one direction. In FIG. 11, the first pipe P1 and the second pipe P2 are arranged in the left-right direction, and the liquid pipe P3 and the gas pipes P4 and P5 are arranged in the up-down direction. Thus, in this embodiment, of the five refrigerant pipes, the first pipe P1 and the second pipe P2 of the first circuit 5a and the liquid pipe P3 and the gas pipes P4 and P5 of the second circuit, a plurality of pipes are arranged in the up-down direction (the second direction in FIG. 11).

[0123] The second fixing plate 120a4 has a wiring port O2. The wiring port O2 is an opening for drawing out wiring connected to the electrical component 90. For this reason, wiring passes through the wiring port O2. Here, a plurality of wires are drawn out from the wiring port O2.

[0124] The piping port O1 is formed on the front surface 120a in a range from one end in the first direction (the left end in the left-right direction in FIG. 8) to 1 / 3, preferably 1 / 5 of the first direction width. The wiring port O2 is formed on the front surface 120a in a range from the other end in the first direction (the right end in the left-right direction in FIG. 8) to 1 / 3, preferably 1 / 5 of the first direction width.

[0125] A first direction (left-right direction) of the front surface 120a in which the piping port O1 and the wiring port O2 are formed is the longitudinal direction of the front surface 120a.

[0126] The piping outlet O1 and the wiring outlet O2 are located below the center in the up-down direction. Here, the piping outlet O1 and the wiring outlet O2 are formed at one end in the second direction (the lower end in the up-down direction in FIG. 8) on the front surface 120a. Specifically, the piping outlet O1 and the wiring outlet O2 are formed near the bottom surface 120f.

[0127] (5-2-2) First connection part and second connection part The cascade unit 2 has the above-mentioned first connection part C1 and second connection part C2. The first connection part C1 and the second connection part C2 are located near the cascade casing 2x inside or outside the cascade casing 2x.

[0128] The first connection part C1 is a portion of the first pipe P1 and the second pipe P2 extending from the cascade heat exchanger 35 that is connected to the first pipe P1 and the second pipe P2 extending from the first heat exchanger 74. In FIG. 9, the first connection part C1 is an end of the first refrigerant pipe 113 that is left uncut, and an end of the second refrigerant pipe 114 that is left uncut.

[0129] The second connection part C2 is a part of the liquid pipe P3 and the gas pipes P4 and P5 extending from the cascade heat exchanger 35 that are connected to the liquid pipe P3 and the gas pipes P4 and P5 extending from the second heat exchangers 52a, 52b, and 52c. In FIG. 9, the second connection part C2 is a fifth stop valve 31 (C21), a third stop valve 32 (C22), and a fourth stop valve 33 (C23) housed in the cascade casing 2x. In detail, the fifth stop valve 31 is the second connection part C21 of the liquid pipe P3. The third stop valve 32 is the second connection part C22 of the first gas pipe P4. The fourth stop valve 33 is the second connection part C23 of the second gas pipe P5.

[0130] The first connection part C1 and the second connection part C2 are disposed in close proximity to each other. The term "close" refers to a distance of 0.5 times or less the width (longitudinal length) of the cascade casing 2x. In detail, the first connection part C1 and the second connection part C2 are located within a distance of 0.5 times or less the left-right width of the front surface 120a.

[0131] In this embodiment, in the cascade casing 2x, the portions (drawing positions) through which the first pipe P1 and the second pipe P2 of the first circuit 5a and the liquid pipe P3 and the gas pipes P4 and P5 of the second circuit 10 pass are arranged in the vicinity of each other. In other words, in the cascade casing 2x, the two first pipes P1 and the second pipe P2 of the first circuit 5a and the three liquid pipes P3 and the gas pipes P4 and P5 of the second circuit 10 are arranged in the vicinity of each other. Here, as described above, the two first pipes P1 and the second pipe P2 of the first circuit 5a and the three liquid pipes P3 and the gas pipes P4 and P5 of the second circuit 10 are gathered at the pipe opening O1 which is one opening.

[0132] The first connection part C1 and the second connection part C2 may be located inside the cascade casing 2x or outside the cascade casing 2x. Therefore, at a predetermined position (piping port O1 in FIG. 8) of the cascade casing 2x, there are cases where the communication pipes 111 and 112 are located (the first connection part C1 is inside the cascade casing 2x) ​​and cases where the first refrigerant pipe 113 and the second refrigerant pipe 114 are located (the first connection part C1 is outside the casing). At a predetermined position (piping port O1 in FIG. 8) of the cascade casing 2x, there are cases where the communication pipes 7, 8, and 9 are located (the second connection part C2 is inside the cascade casing 2x) ​​and cases where the liquid pipe P3 and the gas pipes P4 and P5 extending from the cascade heat exchanger 35 are located (the second connection part C2 is outside the cascade casing 2x).

[0133] The first connection part C1 and the second connection part C2 are located on one side (the left side in FIG. 8) of the center in the left-right direction of the front surface 120a when viewed from the front surface 120a. In this manner, in this embodiment, the first connection part C1 and the second connection part C2 are located on the same side surface side with respect to the center in the left-right direction of the cascade casing 2x.

[0134] The first connection portion C1 and the second connection portion C2 are located below the center in the up-down direction. Here, the first connection portion C1 is located below the second connection portion C2.

[0135] The liquid pipe P3 and the gas pipes P4 and P5 in which carbon dioxide is sealed are arranged at a distance from each other. Specifically, as shown in Fig. 9, the distance L2 between the second connection part C21 of the liquid pipe P3 and the second connection parts C22 and C23 of the gas pipes P4 and P5 is greater than the distance L1 between the first connection part C11 of the first pipe P1 and the first connection part C12 of the second pipe P2. The distance L2 between the second connection part C21 of the liquid pipe P3 and the second connection parts C22 and C23 of the gas pipes P4 and P5 is the distance between the first gas pipe P4 and the second gas pipe P5 and the gas pipes in the direction closer to the liquid pipe P3.

[0136] 11, at the pipe port O1 of the cascade casing 2x, the distance L2 between the liquid pipe P3 and the first gas pipe P4 is greater than the distance L1 between the first pipe P1 and the first connection part C12 of the second pipe P2. At the pipe port O1 of the cascade casing 2x, the distance L2 between the first gas pipe P4 and the second gas pipe P5 is greater than the distance L1 between the first pipe P1 and the first connection part C12 of the second pipe P2.

[0137] In addition, the distance L2 between the second connection part C21 of the liquid pipe P3 and the second connection part C22 of the first gas pipe P4, and the distance L2 between the second connection part C22 of the first gas pipe P4 and the second connection part C23 of the second gas pipe P5 may be different, but are the same in this embodiment.

[0138] 12, the liquid pipe P3 and the gas pipes P4 and P5 extending from the second heat exchangers 52a, 52b, and 52c are connected to the third stop valve 32, the fourth stop valve 33, and the fifth stop valve 31 via joint members J1, J2, and J3, respectively. The joint members J1, J2, and J3 are, for example, bent pipes. The liquid pipe P3 and the gas pipes P4 and P5 are pipes extending straight, and are connected to the curved portions using the joint members J1, J2, and J3.

[0139] (5-2-3) Relationship between cascade unit and first unit 7, in this embodiment, the first unit 5 is arranged next to the side of the cascade unit 2. Therefore, the cascade unit 2 and the first unit 5 are arranged next to each other on the rooftop of a building.

[0140] Here, the communication pipes 111, 112 connecting the cascade unit 2 and the first unit 5 are drawn out horizontally from the pipe port O1 of the cascade casing 2x. The communication pipes 7, 8, 9 connecting the cascade unit 2 and the second units 4a, 4b, 4c are also drawn out horizontally from the pipe port O1.

[0141] (6) Second Unit The second units 4a, 4b, and 4c include utilization units 3a, 3b, and 3c, branching units 6a, 6b, and 6c, first connecting pipes 15a, 15b, and 15c, and second connecting pipes 16a, 16b, and 16c.

[0142] (6-1) Usage unit The utilization units 3a, 3b, and 3c are installed in a room of a building or the like by being embedded in or suspended from the ceiling, or by being hung on a wall surface of the room.

[0143] The utilization units 3 a , 3 b , and 3 c are connected to the cascade unit 2 via interconnecting pipes 7 , 8 , and 9 .

[0144] The utilization units 3 a, 3 b, and 3 c have utilization circuits 13 a, 13 b, and 13 c that constitute a part of the second circuit 10.

[0145] The configurations of the usage units 3a, 3b, and 3c will be described below. Note that the second usage unit 3b and the third usage unit 3c have the same configuration as the first usage unit 3a, so only the configuration of the first usage unit 3a will be described here, and for the configurations of the second usage unit 3b and the third usage unit 3c, the suffix "b" or "c" will be added instead of the suffix "a" of the reference numerals indicating the respective parts of the first usage unit 3a, and the description of each part will be omitted.

[0146] The first utilization unit 3a mainly includes the utilization circuit 13a, a second fan 53a, a utilization side control unit 50a, and various sensors. The second fan 53a includes a second fan motor 54a.

[0147] The second fan 53a draws indoor air into the utilization unit 3a, exchanges heat with the refrigerant flowing through the second heat exchanger 52a, and generates an air flow to be supplied to the room as supply air. The second fan 53a is driven by a second fan motor 54a.

[0148] 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 second heat exchanger 52a. The utilization unit 3a is also provided with an indoor temperature sensor 55a that detects the indoor temperature, which is the temperature of air taken in from the room before passing through the second heat exchanger 52a.

[0149] The usage-side control section 50a controls the operation of each of the members 51a, 53a (54a) that constitute the usage unit 3a. The usage-side control section 50a has a processor, such as a CPU or a microcomputer, and a memory that are provided to control the usage unit 3a, and is capable of exchanging control signals and the like with a remote control (not shown), as well as with the heat-source-side control section 20 of the cascade unit 2, the branching unit control sections 60a, 60b, 60c, and the first control section 70 of the first unit 5.

[0150] The second usage unit 3b has a usage circuit 13b, a second fan 53b, a usage side controller 50b, and a second fan motor 54b. The third usage unit 3c has a usage circuit 13c, a second fan 53c, a usage side controller 50c, and a second fan motor 54c.

[0151] (6-2) Branch unit The branching units 6a, 6b, and 6c are installed in a space above the ceiling in a room of a building or the like.

[0152] The branching units 6a, 6b, and 6c are connected to the utilization units 3a, 3b, and 3c in a one-to-one correspondence. The branching units 6a, 6b, and 6c are connected to the cascade unit 2 via connection pipes 7, 8, and 9.

[0153] Next, the configurations of the branching units 6a, 6b, and 6c will be described. Note that the second branching unit 6b and the third branching unit 6c have the same configuration as the first branching unit 6a, so only the configuration of the first branching unit 6a will be described here, and for the configurations of the second branching unit 6b and the third branching unit 6c, the suffix "b" or "c" will be added instead of the suffix "a" of the reference numerals indicating the respective parts of the first branching unit 6a, and the description of each part will be omitted.

[0154] The first branching unit 6a mainly includes the above-mentioned branching circuit 14a and a branching unit control section 60a.

[0155] The branching unit control section 60a controls the operation of each of the members 66a and 67a that constitute the branching unit 6a. The branching unit control section 60a has a processor, such as a CPU or a microcomputer, and a memory that are provided to control the branching unit 6a, and is capable of exchanging control signals and the like with a remote control (not shown), as well as with the heat source side control section 20 of the cascade unit 2, the utilization units 3a, 3b, and 3c, and the first control section 70 of the first unit 5.

[0156] The second branching unit 6b includes a branching circuit 14b and a branching unit control unit 60b, and the third branching unit 6c includes a branching circuit 14c and a branching unit control unit 60c.

[0157] (7) Control section In the refrigeration system 1, the above-mentioned heat source side control unit 20, usage side control units 50a, 50b, 50c, branching unit control units 60a, 60b, 60c, and first control unit 70 are connected to each other so as to be able to communicate with each other via wired or wireless communication, thereby forming a control unit 80. Therefore, this control unit 80 controls the operation of each member 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, 104a, etc. based on detection information from various sensors 37, 38, 39, 83, 84, 85, 86, 87, 88, 77, 78, 79, 81, 82, 58a, 58b, 58c, etc. and instruction information received from a remote control or the like not shown.

[0158] (8) Refrigeration system operation Next, the operation of the refrigeration system 1 will be described with reference to FIGS.

[0159] The refrigeration cycle operation of the refrigeration system 1 can be mainly divided into a cooling operation, a heating operation, a cooling-dominated operation, and a heating-dominated operation.

[0160] Here, the cooling operation is a refrigeration cycle operation in which only utilization units exist in which the second heat exchangers 52a, 52b, 52c function as evaporators of the second refrigerant, and the cascade heat exchanger 35 functions as a radiator of the second refrigerant for the evaporation load of the entire utilization units.

[0161] The heating operation is a refrigeration cycle operation in which only utilization units exist in which the second heat exchangers 52a, 52b, 52c function as radiators of the second refrigerant, and the cascade heat exchanger 35 functions as an evaporator of the second refrigerant for the heat dissipation load of the entire utilization units.

[0162] The cooling-dominated operation is an operation in which a utilization unit in which the second heat exchangers 52a, 52b, and 52c function as evaporators of the second refrigerant and a utilization unit in which the second heat exchangers 52a, 52b, and 52c function as radiators of the refrigerant are mixed together. The cooling-dominated operation is a refrigeration cycle operation in which, when the evaporative load is the main component of the heat load of the entire utilization unit, the cascade heat exchanger 35 is made to function as a radiator of the second refrigerant to process the evaporative load of the entire utilization unit.

[0163] The heating-dominated operation is an operation in which a utilization unit in which the second heat exchangers 52a, 52b, and 52c function as refrigerant evaporators and a utilization unit in which the second heat exchangers 52a, 52b, and 52c function as refrigerant radiators are mixed together. The heating-dominated operation is a refrigeration cycle operation in which, when the heat radiation load is the main component of the heat load of the entire utilization unit, the cascade heat exchanger 35 is made to function as an evaporator of the second refrigerant to process the heat radiation load of the entire utilization unit.

[0164] The operation of the refrigeration system 1, including these refrigeration cycle operations, is performed by the control unit 80 described above.

[0165] (8-1) Cooling operation In the cooling operation, for example, all of the second heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c function as evaporators of the refrigerant, and the cascade heat exchanger 35 functions as a radiator of the second refrigerant. In this cooling operation, the first circuit 5a and the second circuit 10 of the refrigeration system 1 are configured as shown in Fig. 3. Note that the arrows attached to the first circuit 5a and the second circuit 10 in Fig. 3 indicate the flow of the refrigerant during the cooling operation.

[0166] Specifically, in the first unit 5, the cascade heat exchanger 35 is made to function as an evaporator of the first refrigerant by switching the first switching mechanism 72 to the fifth connection state. The fifth connection state of the first switching mechanism 72 is the connection state shown by the solid line in the first switching mechanism 72 in FIG. 3. As a result, in the first unit 5, the first refrigerant discharged from the first compressor 71 passes through the first switching mechanism 72 and is condensed in the first heat exchanger 74 by heat exchange with outside air supplied from the first fan 75. The first refrigerant condensed in the first heat exchanger 74 passes through the first expansion valve 76 controlled to a fully open state, and a part of the refrigerant flows toward the second stop valve 108 through the first supercooling heat exchanger 103, and the other part of the refrigerant branches off and flows into the first supercooling circuit 104. The refrigerant flowing through the first supercooling circuit 104 is decompressed when passing through the first supercooling expansion valve 104a. The refrigerant flowing from the first expansion valve 76 toward the second shutoff valve 108 exchanges heat with the refrigerant decompressed by the first subcooling expansion valve 104a and flowing through the first subcooling circuit 104 in the first subcooling heat exchanger 103, and is cooled until it is in a subcooled state. The refrigerant in the subcooled state passes through the second connection pipe 111, and the first refrigerant is decompressed when passing through the second expansion valve 102. Here, the valve opening degree of the second expansion valve 102 is controlled so that the superheat degree of the first refrigerant sucked into the first compressor 71 satisfies a predetermined condition. The first refrigerant decompressed by the second expansion valve 102 evaporates by exchanging heat with the second refrigerant flowing through the second passage 35a when flowing through the first passage 35b of the cascade heat exchanger 35, and flows toward the first connection pipe 112. This first refrigerant passes through the first connection pipe 112 and the first shutoff valve 109, and then reaches the first switching mechanism 72. The refrigerant that has passed through the first switching mechanism 72 merges with the refrigerant that has flowed through the first subcooling circuit 104, and is then sucked into the first compressor 71 via the first accumulator 105.

[0167] In the cascade unit 2, the second switching mechanism 22 is switched to the first connection state to cause the cascade heat exchanger 35 to function as a radiator of the second refrigerant. In the first connection state of the second switching mechanism 22, the discharge flow path 24 and the third heat source pipe 25 are connected by the first switching valve 22a, and the first heat source pipe 28 and the suction flow path 23 are connected by the second switching valve 22b. Here, the opening degree of the heat source side expansion valve 36 is adjusted. In the first to third utilization units 3a, 3b, and 3c, the second adjustment valves 67a, 67b, and 67c are controlled to be in an open state. As a result, all of the second heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c function as evaporators of the refrigerant. In addition, all of the second heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c are connected to the suction side of the second compressor 21 of the cascade unit 2 via the first utilization pipes 57a, 57b, and 57c, the first connecting pipes 15a, 15b, and 15c, the junction pipes 62a, 62b, and 62c, the second branch pipes 64a, 64b, and 64c, the bypass pipes 69a, 69b, and 69c, a part of the first branch pipes 63a, 63b, and 63c, the fourth connecting pipe 8, and the fifth connecting pipe 9. In addition, the second supercooling expansion valve 48a is controlled in opening degree so that the degree of supercooling of the second refrigerant flowing from the outlet of the second supercooling heat exchanger 47 toward the third connecting pipe 7 satisfies a predetermined condition. The bypass expansion valve 46a is controlled to a closed state. In the utilization units 3a, 3b, and 3c, the utilization side expansion valves 51a, 51b, and 51c have their openings adjusted.

[0168] In the second circuit 10, the high-pressure second refrigerant compressed and discharged by the second compressor 21 is sent to the second flow path 35a of the cascade heat exchanger 35 through the first switching valve 22a of the second switching mechanism 22. In the cascade heat exchanger 35, the high-pressure second refrigerant flowing through the second flow path 35a dissipates heat, and the first refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35 evaporates. The second refrigerant that has dissipated heat in the cascade heat exchanger 35 passes through the heat source side expansion valve 36, the opening of which is adjusted, and then flows into the second receiver 45. A part of the second refrigerant that flows out of the second receiver 45 branches off and flows into the second supercooling circuit 48, and is depressurized in the second supercooling expansion valve 48a before joining the suction flow path 23. In the second subcooling heat exchanger 47, another portion of the refrigerant flowing out from the second receiver 45 is cooled by the refrigerant flowing through the second subcooling circuit 48, and then sent to the third connecting pipe 7 through the fifth shut-off valve 31.

[0169] The refrigerant sent to the third connection pipe 7 is then branched into three and passes through the third branch pipes 61a, 61b, and 61c of the first to third branch units 6a, 6b, and 6c. The refrigerant that has flowed through the second connection pipes 16a, 16b, and 16c is then sent to the second utilization pipes 56a, 56b, and 56c of the first to third utilization units 3a, 3b, and 3c. The refrigerant sent to the second utilization pipes 56a, 56b, and 56c is sent to the utilization side expansion valves 51a, 51b, and 51c of the utilization units 3a, 3b, and 3c.

[0170] Then, the second refrigerant that has passed through the utilization side expansion valves 51a, 51b, 51c, the opening of which has been adjusted, exchanges heat with the indoor air supplied by the second fans 53a, 53b, 53c in the second heat exchangers 52a, 52b, 52c. As a result, the second refrigerant flowing through the second heat exchangers 52a, 52b, 52c evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant that has evaporated in the second heat exchangers 52a, 52b, 52c flows through the first utilization pipes 57a, 57b, 57c, and the first connecting pipes 15a, 15b, 15c, and is then sent to the junction pipes 62a, 62b, 62c of the first to third branching units 6a, 6b, 6c.

[0171] The low-pressure gas refrigerant sent to the junction pipes 62a, 62b, 62c flows to the second branch pipes 64a, 64b, 64c. A portion of the second refrigerant that has passed through the second control valves 67a, 67b, 67c in the second branch pipes 64a, 64b, 64c is sent to the fifth connection pipe 9. The remaining portion of the refrigerant that has passed through the second control valves 67a, 67b, 67c passes through bypass pipes 69a, 69b, 69c, flows through portions of the first branch pipes 63a, 63b, 63c, and is then sent to the fourth connection pipe 8.

[0172] Then, the low-pressure gas refrigerant sent to the fourth connecting pipe 8 and the fifth connecting pipe 9 is returned to the suction side of the second compressor 21 through the third shut-off valve 32, the fourth shut-off valve 33, the first heat source pipe 28, the second heat source pipe 29, the second switching valve 22b of the second switching mechanism 22, the suction passage 23 and the second accumulator 30.

[0173] In the cooling operation, the capacity control is performed in the second circuit 10, for example, by controlling the second compressor 21 so that the evaporation temperature of the second refrigerant in the second heat exchangers 52a, 52b, and 52c becomes a predetermined evaporation target temperature. In the first circuit 5a, the capacity control is performed, for example, by controlling the first compressor 71 so that the evaporation temperature of the first refrigerant in the first flow path 35b of the cascade heat exchanger 35 becomes a predetermined evaporation target temperature. Here, the evaporation target temperature is changed so that the carbon dioxide refrigerant flowing through the second flow path 35a of the cascade heat exchanger 35 does not exceed the critical point when the predetermined operating condition is not such that the carbon dioxide refrigerant exceeds the critical point, and is changed so that the critical point is exceeded by a predetermined amount when the predetermined operating condition is such that the carbon dioxide refrigerant exceeds the critical point.

[0174] In this manner, the cooling operation is carried out.

[0175] (8-2) Heating operation In the heating operation, for example, all of the second heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c function as radiators of the refrigerant. In the heating operation, the cascade heat exchanger 35 functions as an evaporator of the second refrigerant. In the heating operation, the first circuit 5a and the second circuit 10 of the refrigeration system 1 are configured as shown in Fig. 4. The arrows on the first circuit 5a and the arrows on the second circuit 10 in Fig. 4 indicate the flow of the refrigerant during the heating operation.

[0176] Specifically, in the first unit 5, the first switching mechanism 72 is switched to the sixth operating state to cause the cascade heat exchanger 35 to function as a radiator for the first refrigerant. The sixth operating state of the first switching mechanism 72 is the connection state shown by the dashed line in the first switching mechanism 72 in FIG. 4. As a result, in the first unit 5, the first refrigerant discharged from the first compressor 71 and passing through the first switching mechanism 72 passes through the first connection pipe 112 and is sent to the first flow path 35b of the cascade heat exchanger 35. The refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35 is condensed by heat exchange with the second refrigerant flowing through the second flow path 35a. The first refrigerant condensed in the cascade heat exchanger 35 passes through the second expansion valve 102 controlled to a fully open state while flowing through the second refrigerant pipe 114. The refrigerant that has passed through the second expansion valve 102 flows through the second connection pipe 111, the second closing valve 108, and the first subcooling heat exchanger 103 in this order, and is decompressed in the first expansion valve 76. During heating operation, the first subcooling expansion valve 104a is controlled to a closed state, so that no refrigerant flows through the first subcooling circuit 104, and no heat exchange is performed in the first subcooling heat exchanger 103. The first expansion valve 76 has a valve opening controlled so that the degree of superheat of the first refrigerant drawn into the first compressor 71 satisfies a predetermined condition. The refrigerant that has been decompressed in the first expansion valve 76 evaporates by exchanging heat with outside air supplied from the first fan 75 in the first heat exchanger 74, passes through the first switching mechanism 72 and the first accumulator 105, and is drawn into the first compressor 71.

[0177] In addition, in the cascade unit 2, the second switching mechanism 22 is switched to the second connection state. This allows the cascade heat exchanger 35 to function as an evaporator of the second refrigerant. In the second connection state of the second switching mechanism 22, the discharge flow path 24 and the first heat source pipe 28 are connected by the second switching valve 22b, and the third heat source pipe 25 and the suction flow path 23 are connected by the first switching valve 22a. In addition, the opening degree of the heat source side expansion valve 36 is adjusted. In the first to third branch units 6a, 6b, and 6c, the first adjustment valves 66a, 66b, and 66c are controlled to be in an open state, and the second adjustment valves 67a, 67b, and 67c are controlled to be in a closed state. This allows all of the second heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c to function as radiators of the refrigerant. The second heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c are connected to the discharge side of the second compressor 21 of the cascade unit 2 via the discharge flow path 24, the first heat source pipe 28, the fourth connection pipe 8, the first branch pipes 63a, 63b, and 63c, the junction pipes 62a, 62b, and 62c, the first connection pipes 15a, 15b, and 15c, and the first utilization pipes 57a, 57b, and 57c. The second supercooling expansion valve 48a and the bypass expansion valve 46a are controlled to be in a closed state. In the utilization units 3a, 3b, and 3c, the utilization side expansion valves 51a, 51b, and 51c are adjusted in opening degree.

[0178] In such a second circuit 10, the high-pressure second refrigerant compressed and discharged by the second compressor 21 is sent to the first heat source piping 28 through the second switching valve 22b of the second switching mechanism 22. The refrigerant sent to the first heat source piping 28 is sent to the fourth connection piping 8 through the third stop valve 32.

[0179] The high-pressure refrigerant sent to the fourth connection pipe 8 is then branched into three and sent to the first branch pipes 63a, 63b, and 63c of the utilization units 3a, 3b, and 3c that are in operation. The high-pressure second refrigerant sent to the first branch pipes 63a, 63b, and 63c passes through the first control valves 66a, 66b, and 66c, and flows through the junction pipes 62a, 62b, and 62c. The refrigerant then flows through the first connection pipes 15a, 15b, and 15c and the first utilization pipes 57a, 57b, and 57c, and is sent to the second heat exchangers 52a, 52b, and 52c.

[0180] The high-pressure second refrigerant sent to the second heat exchangers 52a, 52b, 52c exchanges heat with the indoor air supplied by the second fans 53a, 53b, 53c in the second heat exchangers 52a, 52b, 52c. As a result, the second refrigerant flowing through the second heat exchangers 52a, 52b, 52c dissipates heat. The indoor air is heated and supplied to the room. As a result, the indoor space is heated. The second refrigerant that dissipates heat in the second heat exchangers 52a, 52b, 52c flows through the second utilization pipes 56a, 56b, 56c and passes through the utilization side expansion valves 51a, 51b, 51c whose opening degree is adjusted. After that, the refrigerant that flows through the second connection pipes 16a, 16b, 16c flows through the third branch pipes 61a, 61b, 61c of the branch units 6a, 6b, 6c.

[0181] The second refrigerant sent to the third branch pipes 61a, 61b, 61c is sent to the third connection pipe 7 and merges therewith.

[0182] The second refrigerant sent to the third communication pipe 7 is sent to the heat source side expansion valve 36 through the fifth shutoff valve 31. The refrigerant sent to the heat source side expansion valve 36 has its flow rate adjusted in the heat source side expansion valve 36, and is then sent to the cascade heat exchanger 35. In the cascade heat exchanger 35, the second refrigerant flowing through the second flow path 35a evaporates to become a low-pressure gas refrigerant and is sent to the second switching mechanism 22, and the first refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35 condenses. The low-pressure gas refrigerant sent to the first switching valve 22a of the second switching mechanism 22 is returned to the suction side of the second compressor 21 through the suction flow path 23 and the second accumulator 30.

[0183] In the heating operation, the capacity control is performed in the second circuit 10, for example, by controlling the second compressor 21 so as to process the load in the second heat exchangers 52a, 52b, and 52c. In the first circuit 5a, the capacity control is performed, for example, by controlling the first compressor 71 so that the condensation temperature of the first refrigerant in the first flow path 35b of the cascade heat exchanger 35 becomes a predetermined condensation target temperature.

[0184] In this manner, the operation in the heating mode is carried out.

[0185] (8-3) Cooling-dominant operation In the cooling-dominated operation, for example, the second heat exchangers 52a, 52b of the utilization units 3a, 3b function as refrigerant evaporators, and the second heat exchanger 52c of the utilization unit 3c functions as a refrigerant radiator. In the cooling-dominated operation, the cascade heat exchanger 35 functions as a radiator of the second refrigerant. In the cooling-dominated operation, the first circuit 5a and the second circuit 10 of the refrigeration system 1 are configured as shown in Fig. 5. The arrows attached to the first circuit 5a and the second circuit 10 in Fig. 5 indicate the flow of the refrigerant during the cooling-dominated operation.

[0186] Specifically, in the first unit 5, the first switching mechanism 72 is switched to the fifth connection state (the state shown by the solid line of the first switching mechanism 72 in FIG. 5 ) to make the cascade heat exchanger 35 function as an evaporator of the first refrigerant. As a result, in the first unit 5, the first refrigerant discharged from the first compressor 71 passes through the first switching mechanism 72 and is condensed in the first heat exchanger 74 by heat exchange with outside air supplied from the first fan 75. The first refrigerant condensed in the first heat exchanger 74 passes through the first expansion valve 76 controlled to a fully open state, and a part of the refrigerant flows toward the second stop valve 108 through the first supercooling heat exchanger 103, and the other part of the refrigerant branches off and flows into the first supercooling circuit 104. The refrigerant flowing through the first supercooling circuit 104 is decompressed when passing through the first supercooling expansion valve 104a. The refrigerant flowing from the first expansion valve 76 toward the second shutoff valve 108 exchanges heat with the refrigerant decompressed by the first subcooling expansion valve 104a and flowing through the first subcooling circuit 104 in the first subcooling heat exchanger 103, and is cooled until it is in a subcooled state. The refrigerant in the subcooled state flows through the second connection pipe 111 and is decompressed by the second expansion valve 102. At this time, the valve opening degree of the second expansion valve 102 is controlled so that the degree of superheat of the refrigerant sucked into the first compressor 71 satisfies a predetermined condition, for example. The first refrigerant decompressed by the second expansion valve 102 evaporates by exchanging heat with the second refrigerant flowing through the second passage 35a while flowing through the first passage 35b of the cascade heat exchanger 35, and flows toward the first connection pipe 112. This first refrigerant passes through the first connection pipe 112 and the first shutoff valve 109, and then reaches the first switching mechanism 72. The refrigerant that has passed through the first switching mechanism 72 merges with the refrigerant that has flowed through the first subcooling circuit 104, and is then sucked into the first compressor 71 via the first accumulator 105.

[0187] In the cascade unit 2, the second switching mechanism 22 is switched to a third connection state in which the discharge flow path 24 and the third heat source pipe 25 are connected by the first switching valve 22a, and the discharge flow path 24 and the first heat source pipe 28 are connected by the second switching valve 22b, so that the cascade heat exchanger 35 functions as a radiator of the second refrigerant. In addition, the opening degree of the heat source side expansion valve 36 is adjusted. In the first to third branch units 6a, 6b, and 6c, the first control valve 66c and the second control valves 67a and 67b are controlled to an open state, and the first control valves 66a, 66b, and the second control valve 67c are controlled to a closed state. As a result, the second heat exchangers 52a and 52b of the utilization units 3a and 3b function as evaporators of the refrigerant, and the second heat exchanger 52c of the utilization unit 3c functions as a radiator of the refrigerant. The second heat exchangers 52a, 52b of the utilization units 3a, 3b are connected to the suction side of the second compressor 21 of the cascade unit 2 via the fifth connection pipe 9, and the second heat exchanger 52c of the utilization unit 3c is connected to the discharge side of the second compressor 21 of the cascade unit 2 via the fourth connection pipe 8. The second supercooling expansion valve 48a is controlled to have an opening degree such that the degree of supercooling of the second refrigerant flowing from the outlet of the second supercooling heat exchanger 47 toward the third connection pipe 7 satisfies a predetermined condition. The bypass expansion valve 46a is controlled to a closed state. In the utilization units 3a, 3b, 3c, the utilization side expansion valves 51a, 51b, 51c are adjusted in opening degree.

[0188] In such a second circuit 10, a portion of the high-pressure second refrigerant compressed and discharged by the second compressor 21 is sent to the fourth connection pipe 8 through the second switching valve 22b of the second switching mechanism 22, the first heat source pipe 28, and the third shut-off valve 32, and the remainder is sent to the second flow path 35a of the cascade heat exchanger 35 through the first switching valve 22a of the second switching mechanism 22 and the third heat source pipe 25.

[0189] The high-pressure refrigerant sent to the fourth connection pipe 8 is then sent to the first branch pipe 63c. The high-pressure refrigerant sent to the first branch pipe 63c is sent to the second heat exchanger 52c of the utilization unit 3c through the first control valve 66c and the junction pipe 62c.

[0190] The high-pressure refrigerant sent to the second heat exchanger 52c exchanges heat with the indoor air supplied by the second fan 53c in the second heat exchanger 52c. As a result, the second refrigerant flowing through the second heat exchanger 52c dissipates heat. The indoor air is heated and supplied to the room, and the heating operation of the utilization unit 3c is performed. The second refrigerant that has dissipated heat in the second heat exchanger 52c flows through the second utilization pipe 56c and has its flow rate adjusted by the utilization side expansion valve 51c. After that, the second refrigerant that has flowed through the second connecting pipe 16c is sent to the third branch pipe 61c of the branch unit 6c.

[0191] The second refrigerant sent to the third branch pipe 61c is then sent to the third connection pipe 7.

[0192] In addition, the high-pressure refrigerant sent to the second flow path 35a of the cascade heat exchanger 35 dissipates heat by exchanging heat with the first refrigerant flowing through the first flow path 35b in the cascade heat exchanger 35. The second refrigerant that has dissipated heat in the cascade heat exchanger 35 is adjusted in flow rate in the heat source side expansion valve 36, and then flows into the second receiver 45. A part of the second refrigerant that has flowed out from the second receiver 45 branches off and flows into the second supercooling circuit 48, and after being depressurized in the second supercooling expansion valve 48a, it merges with the suction flow path 23. In the second supercooling heat exchanger 47, another part of the refrigerant that has flowed out from the second receiver 45 is cooled by the refrigerant flowing through the second supercooling circuit 48, and then sent to the third connection pipe 7 through the fifth stop valve 31, and merges with the refrigerant that has dissipated heat in the second heat exchanger 52c.

[0193] Then, the refrigerant that joins in the third connection pipe 7 branches into two and is sent to the third branch pipes 61a, 61b of the branch units 6a, 6b. After that, the refrigerant that flows through the second connection pipes 16a, 16b is sent to the second usage pipes 56a, 56b of the first and second usage units 3a, 3b. The refrigerant that flows through the second usage pipes 56a, 56b passes through the usage side expansion valves 51a, 51b of the usage units 3a, 3b.

[0194] Then, the refrigerant that has passed through the utilization side expansion valves 51a, 51b, the opening of which has been adjusted, exchanges heat with the indoor air supplied by the second fans 53a, 53b in the second heat exchangers 52a, 52b. As a result, the refrigerant flowing through the second heat exchangers 52a, 52b evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the second heat exchangers 52a, 52b is sent to the junction pipes 62a, 62b of the first and second branch units 6a, 6b.

[0195] Then, the low-pressure gas refrigerant sent to the junction pipes 62a, 62b passes through the second control valves 67a, 67b and the second branch pipes 64a, 64b and is sent to the fifth connection pipe 9 where it joins with the second control valves 67a, 67b and the second branch pipes 64a, 64b.

[0196] Then, the low-pressure gas refrigerant sent to the fifth connection pipe 9 passes through the fourth stop valve 33, the second heat source pipe 29, the suction passage 23 and the second accumulator 30, and is returned to the suction side of the second compressor 21.

[0197] In the cooling-dominated operation, the capacity control is performed in the second circuit 10 by controlling the second compressor 21 so that the evaporation temperature in the heat exchanger that functions as an evaporator of the second refrigerant among the second heat exchangers 52a, 52b, and 52c becomes a predetermined evaporation target temperature. In the first circuit 5a, the capacity control is performed by controlling the first compressor 71 so that the evaporation temperature of the first refrigerant in the first flow path 35b of the cascade heat exchanger 35 becomes a predetermined evaporation target temperature. Here, the evaporation target temperature is changed so that the carbon dioxide refrigerant flowing through the second flow path 35a of the cascade heat exchanger 35 does not exceed the critical point when the predetermined operating condition is not such that the carbon dioxide refrigerant exceeds the critical point, and is changed so that the critical point is exceeded by a predetermined amount when the predetermined operating condition is such that the carbon dioxide refrigerant exceeds the critical point.

[0198] In this manner, the cooling-dominant operation is performed.

[0199] (8-4) Heating-dominant operation In the heating-dominated operation, for example, the second heat exchangers 52a, 52b of the utilization units 3a, 3b function as refrigerant radiators, and the second heat exchanger 52c functions as a refrigerant evaporator. In the heating-dominated operation, the cascade heat exchanger 35 functions as an evaporator of the second refrigerant. In the heating-dominated operation, the first circuit 5a and the second circuit 10 of the refrigeration system 1 are configured as shown in FIG. 6. The arrows attached to the first circuit 5a and the second circuit 10 in FIG. 6 indicate the flow of the refrigerant during the heating-dominated operation.

[0200] Specifically, in the first unit 5, the first switching mechanism 72 is switched to a sixth operating state, so that the cascade heat exchanger 35 functions as a radiator for the first refrigerant. The sixth operating state of the first switching mechanism 72 is a connection state shown by a dashed line in the first switching mechanism 72 in FIG. 6. As a result, in the first unit 5, the first refrigerant discharged from the first compressor 71, passing through the first switching mechanism 72 and the first stop valve 109 passes through the first connection pipe 112 and is sent to the first flow path 35b of the cascade heat exchanger 35. The refrigerant flowing through the first flow path 35b of the cascade heat exchanger 35 is condensed by exchanging heat with the second refrigerant flowing through the second flow path 35a. The first refrigerant condensed in the cascade heat exchanger 35 passes through the second expansion valve 102 controlled to a fully open state, and then flows through the second connection pipe 111, the second closing valve 108, and the first subcooling heat exchanger 103 in this order, and is decompressed in the first expansion valve 76. During heating-dominated operation, the first subcooling expansion valve 104a is controlled to a closed state, so that no refrigerant flows through the first subcooling circuit 104, and no heat exchange is performed in the first subcooling heat exchanger 103. The first expansion valve 76 is controlled to have a valve opening such that the degree of superheat of the refrigerant drawn into the first compressor 71 satisfies a predetermined condition. The refrigerant decompressed in the first expansion valve 76 evaporates by exchanging heat with outside air supplied from the first fan 75 in the first heat exchanger 74, passes through the first switching mechanism 72 and the first accumulator 105, and is drawn into the first compressor 71.

[0201] In the cascade unit 2, the second switching mechanism 22 is switched to the second connection state. In the second connection state of the second switching mechanism 22, the discharge flow path 24 and the first heat source pipe 28 are connected by the second switching valve 22b, and the third heat source pipe 25 and the suction flow path 23 are connected by the first switching valve 22a. This allows the cascade heat exchanger 35 to function as an evaporator for the second refrigerant. In addition, the opening degree of the heat source side expansion valve 36 is adjusted. In the first to third branch units 6a, 6b, and 6c, the first adjustment valves 66a and 66b and the second adjustment valve 67c are controlled to be in the open state, and the first adjustment valves 66c and the second adjustment valves 67a and 67b are controlled to be in the closed state. As a result, the second heat exchangers 52a and 52b of the utilization units 3a and 3b function as radiators of the refrigerant, and the second heat exchanger 52c of the utilization unit 3c functions as an evaporator of the refrigerant. The second heat exchanger 52c of the utilization unit 3c and the suction side of the second compressor 21 of the cascade unit 2 are connected via the first utilization pipe 57c, the first connecting pipe 15c, the junction pipe 62c, the second branch pipe 64c, and the fifth connecting pipe 9. The second heat exchangers 52a and 52b of the utilization units 3a and 3b and the discharge side of the second compressor 21 of the cascade unit 2 are connected via the discharge flow path 24, the first heat source pipe 28, the fourth connecting pipe 8, the first branch pipes 63a and 63b, the junction pipes 62a and 62b, the first connecting pipes 15a and 15b, and the first utilization pipes 57a and 57b. Further, the second subcooling expansion valve 48a and the bypass expansion valve 46a are controlled to a closed state. In the utilization units 3a, 3b, and 3c, the utilization side expansion valves 51a, 51b, and 51c have their openings adjusted.

[0202] In such a second circuit 10, the high-pressure second refrigerant compressed and discharged by the second compressor 21 is sent to the fourth connecting pipe 8 through the second switching valve 22b of the second switching mechanism 22, the first heat source pipe 28, and the third shut-off valve 32.

[0203] The high-pressure refrigerant sent to the fourth connection pipe 8 is then 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 usage unit 3a and the second usage unit 3b, which are operating usage units. The high-pressure refrigerant sent to the first branch pipes 63a, 63b is sent to the second heat exchangers 52a, 52b of the first usage unit 3a and the second usage unit 3b through the first control valves 66a, 66b, the junction pipes 62a, 62b, and the first connection pipes 15a, 15b.

[0204] The high-pressure second refrigerant sent to the second heat exchangers 52a and 52b exchanges heat with the indoor air supplied by the second fans 53a and 53b in the second heat exchangers 52a and 52b. As a result, the refrigerant flowing through the second heat exchangers 52a and 52b dissipates heat. The indoor air is heated and supplied to the room. As a result, the indoor space is heated. The refrigerant that dissipates heat in the second heat exchangers 52a and 52b flows through the second utilization pipes 56a and 56b and passes through the utilization side expansion valves 51a and 51b whose openings are adjusted. Thereafter, the refrigerant that flows through the second connection pipes 16a and 16b is sent to the third connection pipe 7 via the third branch pipes 61a and 61b of the branch units 6a and 6b.

[0205] Then, a part of the refrigerant sent to the third connection pipe 7 is sent to the third branch pipe 61c of the branch unit 6c, and the remainder is sent through the fifth stop valve 31 to the heat source side expansion valve .

[0206] Then, the refrigerant sent to the third branch pipe 61c flows through the second utilization pipe 56c of the utilization unit 3c via the second connecting pipe 16c, and is sent to the utilization side expansion valve 51c.

[0207] Then, the refrigerant that has passed through the utilization side expansion valve 51c, the degree of opening of which has been adjusted, exchanges heat with the indoor air supplied by the second fan 53c in the second heat exchanger 52c. As a result, the refrigerant flowing through the second heat exchanger 52c evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and supplied to the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant that has evaporated in the second heat exchanger 52c passes through the first utilization pipe 57c and the first connecting pipe 15c, and is sent to the junction pipe 62c.

[0208] Then, the low-pressure gas refrigerant sent to the junction pipe 62c is sent to the fifth connection pipe 9 through the second control valve 67c and the second branch pipe 64c.

[0209] Then, the low-pressure gas refrigerant sent to the fifth connection pipe 9 passes through the fourth stop valve 33, the second heat source pipe 29, the suction passage 23 and the second accumulator 30, and is returned to the suction side of the second compressor 21.

[0210] In addition, the second refrigerant sent to the heat source side expansion valve 36 passes through the heat source side expansion valve 36, the opening of which is adjusted, and then exchanges heat with the first refrigerant flowing through the first flow path 35b in the second flow path 35a of the cascade heat exchanger 35. As a result, the refrigerant flowing through the second flow path 35a of the cascade heat exchanger 35 evaporates and becomes a low-pressure gas refrigerant, and is sent to the first switching valve 22a of the second switching mechanism 22. The low-pressure gas refrigerant sent to the first switching valve 22a of the second switching mechanism 22 merges with the low-pressure gas refrigerant evaporated in the second heat exchanger 52c in the suction flow path 23. The merged refrigerant is returned to the suction side of the second compressor 21 via the second accumulator 30.

[0211] In the heating-dominated operation, the capacity of the second circuit 10 is controlled by, for example, controlling the second compressor 21 so that the load of the heat exchanger that functions as a radiator of the second refrigerant among the second heat exchangers 52a, 52b, and 52c is processed. In the first circuit 5a, the capacity is controlled by, for example, controlling the first compressor 71 so that the condensation temperature of the first refrigerant in the first flow path 35b of the cascade heat exchanger 35 becomes a predetermined condensation target temperature.

[0212] In this manner, the operation in the heating main operation is performed.

[0213] (9) Features (9-1) The cascade unit 2 according to this embodiment is a cascade unit 2 of a refrigeration system 1 having a first circuit 5a, a second circuit 10, and a cascade heat exchanger 35. A heat medium for carrying heat flows through the first circuit 5a. The first circuit 5a has a first heat exchanger 74. The first heat exchanger 74 exchanges heat between a heat source and the heat medium. The second circuit 10 has a second compressor 21 and second heat exchangers 52a, 52b, and 52c. The second compressor 21 compresses a second refrigerant. The second heat exchangers 52a, 52b, and 52c exchange heat between the second refrigerant and indoor air. The second refrigerant circulates through the second circuit 10. The cascade heat exchanger 35 exchanges heat between the heat medium of the first circuit 5a and the second refrigerant of the second circuit 10. The cascade unit 2 includes a cascade heat exchanger 35, a second compressor 21, an electrical component 90, and a cascade casing 2x. The electrical component 90 drives the second compressor 21. The cascade casing 2x houses the cascade heat exchanger 35, the second compressor 21, and the electrical component 90. The cascade casing 2x has a piping port O1 formed in a range from one end (left end in FIG. 8) in the first direction (left-right direction in FIG. 8) to 1 / 3 of the first direction width. The piping port O1 leads out the first piping P1 and the second piping P2 connecting the cascade heat exchanger 35 and the first heat exchanger 74 of the first circuit 5a, and the liquid pipe P3 and the gas pipes P4 and P5 connecting the cascade heat exchanger 35 and the second heat exchangers 52a, 52b, and 52c of the second circuit 10. Further, the cascade casing 2x has a wiring port O2 formed in a range from the other end (the right end in FIG. 8) in the first direction (the left-right direction in FIG. 8) to ⅓ of the width in the first direction. Wiring connected to the electrical equipment 90 is drawn out from the wiring port O2.

[0214] According to the cascade unit 2 of this embodiment, the piping port O1 for leading out the first pipe P1 and the second pipe P2 of the first circuit 5a, the liquid pipe P3 and the gas pipes P4 and P5 of the second circuit 10, and the wiring port O2 for leading out the wiring are arranged apart in the first direction. Therefore, the piping of the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 can be collected at one end of the cascade casing 2x in the first direction, and the wiring can be collected at the other end of the cascade casing 2x in the second direction. As a result, the piping is taken out from the cascade unit 2 to both the first unit 5 and the second units 4a, 4b, and 4c, but since the piping port O1 and the wiring port O2 are sufficiently apart, even if the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are drawn out from the piping port O1 in different directions, the wiring does not get in the way, making it easy to lay out the piping. In this way, it is possible to reduce restrictions on the layout of the piping such as the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 due to wiring, and therefore the degree of freedom in the layout of the piping such as the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 is increased.

[0215] (9-2) In the cascade unit 2 according to this embodiment, the cascade casing 2x preferably has a side surface extending in a first direction (left-right direction in FIG. 8). The piping port O1 and the wiring port O2 are formed on the side surface (front surface 120a in FIG. 8).

[0216] Here, the pipes such as the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 can be collected in a range from one end in the first direction of the side surface (the left end in FIG. 8) to 1 / 3 of the first direction width, and the wiring port O2 can be collected in a range from the other end in the first direction of the side surface (the right end in FIG. 8) to 1 / 3 of the first direction width. This allows for greater freedom in the arrangement of the pipes.

[0217] (9-3) In the cascade unit 2 according to this embodiment, the cascade casing 2x preferably further includes a bottom plate constituting the bottom surface 120f. The cascade heat exchanger 35 is disposed near the pipe port O1 and on the bottom plate.

[0218] Here, the cascade heat exchanger 35 is located near the piping opening O1 and on the bottom plate, so that piping such as the first piping P1, the second piping P2, the liquid pipe P3, and the gas pipes P4, P5 can be shortened and the cascade heat exchanger 35 can be positioned stably.

[0219] (9-4) In the cascade unit 2 according to this embodiment, the cascade casing 2x preferably has a side surface extending in the first direction. When viewed from the side surface (the front surface 120a in FIG. 8), the electrical components 90 and the cascade heat exchanger 35 do not overlap.

[0220] Piping is drawn from the cascade heat exchanger 35 to a piping port O1, and wiring from the electrical equipment 90 is drawn to a wiring port O2. In this case, the electrical equipment 90 and the cascade unit 2 do not overlap when viewed from the front surface 120a, so that an arrangement in which the piping port O1 and the wiring port O2 are separated in the first direction (the left-right direction in FIG. 8) can be easily realized.

[0221] (9-5) In the cascade unit 2 according to this embodiment, the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are preferably arranged in a plurality of different directions at the pipe port O1.

[0222] Here, at the pipe port O1, the direction in which some of the four or more pipes in the cascade casing 2x are lined up (the vertical direction in FIG. 8) differs from the direction in which the other parts are lined up (the horizontal direction in FIG. 8). This makes it possible to easily gather the four or more pipes at the pipe port O1.

[0223] (9-6) In the cascade unit 2 according to this embodiment, the piping port O1 and the wiring port O2 are preferably disposed at one end (lower end in FIG. 8) in a second direction perpendicular to the first direction. The cascade casing 2x has a maintenance opening formed at the other end (upper end in FIG. 8) in the second direction relative to the piping port O1 and the wiring port O2. The cascade casing 2x further has a removable plate (upper plate 120a1 in FIG. 8) that closes the maintenance opening.

[0224] Here, maintenance can be performed through a maintenance opening that is exposed by removing the upper plate 120a1 and the lower plate 120a2 of the front surface 120a. The piping port O1 is arranged at one end in the first direction, and the wiring port O2 is arranged at the other end in the first direction, on the side of one end in the second direction from the maintenance opening, so that the piping and wiring do not protrude from the center. Therefore, when performing maintenance through the maintenance opening, the piping and wiring, such as the first piping P1, the second piping P2, the liquid pipe P3, and the gas pipes P4 and P5, do not get in the way, improving maintainability.

[0225] In particular, if the opening for maintenance is formed at a position higher than the piping port O1 and the wiring port O2, the piping and wiring do not protrude into the central foot area, which further improves maintainability.

[0226] (9-7) In the cascade unit 2 according to this embodiment, the second refrigerant is preferably carbon dioxide.

[0227] Here, carbon dioxide is sealed in the refrigerant piping of the second circuit 10. The refrigerant piping in which carbon dioxide is sealed is required to have high pressure resistance, so the refrigerant piping has a large wall thickness. When brazing is performed during construction, the heat input is large, so the work time is long. The wiring port O2 of this embodiment is disposed on the other end side opposite the pipe port O1 in the first direction, so the wiring can be separated from the refrigerant piping in which carbon dioxide is sealed. This makes it possible to reduce the impact on the wiring caused by the long work time at high temperatures near the pipe port O1.

[0228] (9-8) The refrigeration system 1 according to this embodiment includes a cascade unit 2, a first unit 5, and second units 4a, 4b, and 4c. The first unit 5 includes a first heat exchanger 74. The second units 4a, 4b, and 4c include second heat exchangers 52a, 52b, and 52c.

[0229] Here, in the cascade unit 2, the piping port O1 for leading out the first piping P1 and the second piping P2 of the first circuit 5a, and the liquid pipe P3 and the gas pipes P4 and P5 of the second circuit 410, and the wiring port O2 for leading out the wiring are formed apart in the first direction. Therefore, in the cascade unit 2, restrictions on the layout of the piping due to the wiring can be reduced, and the degree of freedom in the layout of the piping from the cascade unit 2 to the first unit 5 and the second units 4a, 4b, and 4c is increased.

[0230] (10) Variations (10-1) Variation 1 In the above embodiment, the first unit 5 is arranged next to the cascade unit 2, but is not limited to this. In this modification, the first unit 5 is arranged above the cascade unit 2, as shown in FIG.

[0231] Although the first unit 5 may be disposed above the cascade unit 2, in this modification, a mounting table for disposing the first unit thereon is provided above the cascade unit 2.

[0232] In this modification, the communication pipes 111, 112 connecting the cascade unit 2 and the first unit 5 are drawn upward from the pipe port O1 of the cascade casing 2x. Also, the communication pipes 7, 8, 9 connecting the cascade unit 2 and the second units 4a, 4b, 4c are drawn horizontally from the pipe port O1.

[0233] According to this modification, the first unit 5 is disposed above the cascade unit 2. In this modification as well, the first pipe P1 and the second pipe P2 are gathered at a predetermined position of the cascade casing 2x, so that the first pipe P1 and the second pipe P2 can be easily extended from the cascade unit 2 toward the first unit 5 disposed above.

[0234] (10-2) Variation 2 In the above embodiment, the piping port O1 and the wiring port O2 are formed on the front surface 120a of the cascade casing 2x, but are not limited thereto. The piping port O1 and the wiring port O2 may be formed on any surface of the cascade casing 2x. In other words, the piping port O1 and the wiring port O2 may be formed on at least one surface of the front surface 120a, the rear surface 120b, the bottom surface 120f, the top surface 120e, the left surface 120c plate, and the right surface 120d. Preferably, from the viewpoint of reducing the service space, the piping port O1 and the wiring port O2 are formed on at least one surface of the front surface 120a, the bottom surface 120f, the top surface 120e, the left surface 120c plate, and the right surface 120d, except for the rear surface 120b.

[0235] (10-3) Variation 3 In the above embodiment, the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are drawn out from one pipe port O1 of the cascade casing 2x, but this is not limited to this. In this modified example, the first pipe P1, the second pipe P2, the liquid pipe P3, and the gas pipes P4 and P5 are drawn out from multiple pipe ports O1. The multiple pipe ports O1 are arranged in close proximity to each other.

[0236] In the above embodiment, the wiring is drawn out from one wiring port O2, but this is not limited to this. In this modification, multiple wirings are drawn out from multiple wiring ports O2. The multiple wiring ports O2 are arranged close to each other.

[0237] In this case, the multiple piping ports O1 may be formed on one surface, and may not be limited to the front surface 120a, but may be formed on multiple surfaces, such as the bottom surface 120f, the top surface 120e, the left surface 120c, and the right surface 120d, excluding the rear surface 120b. Also, the multiple wiring ports O2 may be formed on one surface, and may not be limited to the front surface 120a, but may be formed on multiple surfaces, such as the bottom surface 120f, the top surface 120e, the left surface 120c, and the right surface 120d, excluding the rear surface 120b.

[0238] In this modification, multiple piping ports O1 and multiple wiring ports O2 are formed on multiple surfaces. The piping ports O1 formed on the multiple surfaces are formed in a range from one end in the left-right direction to 1 / 3 of the left-right width when viewed from the front surface 120a. The wiring ports O2 formed on the multiple surfaces are formed in a range from the other end in the left-right direction to 1 / 3 of the left-right width when viewed from the front surface 120a.

[0239] (10-4) Variation 4 In the above embodiment, the second circuit 10 has three second connection parts C21, C22, and C23, but in this modification, it has two connection parts. In this case, in the second circuit, there is one gas pipe connecting the second heat exchanger and the cascade heat exchanger. This modification is applied to, for example, a configuration in which the multiple utilization units 3a, 3b, and 3c cannot individually perform cooling or heating operation, a configuration in which there is only one second unit, and the like.

[0240] (10-5) Variation 5 In the above embodiment, R32 or R410A is exemplified as the refrigerant used in the first circuit 5a, and carbon dioxide is exemplified as the refrigerant used in the second circuit 10, but the present invention is not limited thereto.

[0241] The refrigerant used in the first circuit 5a may be HFC-32, an HFO refrigerant, a mixed refrigerant of HFC-32 and an HFO refrigerant, carbon dioxide, ammonia, propane, or the like.

[0242] The refrigerant used in the second circuit 10 may be HFC-32, an HFO refrigerant, a mixed refrigerant of HFC-32 and an HFO refrigerant, carbon dioxide, ammonia, propane, or the like.

[0243] As the HFO refrigerant, for example, HFO-1234yf, HFO-1234ze, etc. can be used.

[0244] The first circuit 5a and the second circuit 10 may use the same refrigerant or different refrigerants, but it is preferable that the refrigerant used in the second circuit 10 has at least one of a lower global warming potential (GWP), a lower ozone depletion potential (ODP), a lower flammability, and a lower toxicity than the refrigerant used in the first circuit 5a. In particular, when the total internal volume of the second circuit 10 is larger than the total internal volume of the first circuit 5a, by using a refrigerant in the second circuit 10 that has at least one of a lower global warming potential (GWP), ozone depletion potential (ODP), flammability, and toxicity than the refrigerant in the first circuit 5a, it is possible to minimize the adverse effects of leakage.

[0245] (10-6) Variation 6 In the above embodiment, the first circuit 5a is described as circulating a first refrigerant as a heat medium, but the present invention is not limited to this. A medium other than a refrigerant may be used as a heat medium in the first circuit 5a. In this modification, a heat medium circuit in which a heat medium such as water or brine flows is used instead of the first circuit 5a in which the first refrigerant flows. In this case, the heat medium circuit may have a heat source that functions as a hot or cold source and a pump for circulating the heat medium. In this case, the flow rate can be adjusted by the pump, and the amount of heat can be controlled by the hot or cold source.

[0246] (10-7) Variation 7 In the above embodiment, the first unit 5 is described as an outdoor unit having a first fan 75 for supplying outdoor air that exchanges heat with the first refrigerant to the first heat exchanger 74, but is not limited to this. In this manner, the heat source of the present disclosure is not limited to outdoor air that exchanges heat with the first refrigerant. In this modification, the first unit does not have the first fan 75, and exchanges heat between the first refrigerant and water as a heat source in the first heat exchanger 74.

[0247] (10-8) Variation 8 In the above embodiment, the refrigeration system 1 in which one cascade unit 2 is connected to one first unit 5 has been described as an example, but is not limited thereto. In the refrigeration system 1 of this modification, a plurality of cascade units 2 are connected in parallel to one first unit 5.

[0248] (10-9) Variation 9 In the above embodiment, the refrigeration system 1 in which a plurality of second units 4a, 4b, 4c are connected to one cascade unit 2 has been described as an example, but is not limited thereto. In the refrigeration system of this modification, one second unit is connected to one cascade unit 2.

[0249] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure described in the claims. [Explanation of symbols]

[0250] 1: Refrigeration system 2: Cascade unit 2x: Cascade casing (casing) 4a, 4b, 4c: 2nd unit 5: First unit 5a: 1st circuit 10: 2nd circuit 21: Second compressor (compressor) 35: Cascade heat exchanger 52a, 52b, 52c: 2nd heat exchanger 74: 1st heat exchanger 90: Electrical equipment O1: Pipe outlet O2: Wiring port P1: First pipe P2: Second piping P3:Liquid pipe P4, P5: Gas pipes [Prior art documents] [Patent documents]

[0251] [Patent Document 1] JP 2012-193866 A

Claims

1. A first circuit (5) having a first heat exchanger (74) through which a heat medium for carrying heat flows and which exchanges heat between a heat source and the heat medium; a second circuit (10) including a second compressor that compresses a second refrigerant and a second heat exchanger (52a) that exchanges heat between the second refrigerant and indoor air, and in which the second refrigerant circulates; a cascade heat exchanger (35) for performing heat exchange between the heat medium in the first circuit and the second refrigerant in the second circuit; A cascade unit (2) of a refrigeration system having The cascade heat exchanger; The second compressor (21), An electrical component (90) for driving the second compressor; a casing (2x) that houses the cascade heat exchanger, the second compressor, and the electrical equipment; Equipped with The casing includes: a pipe opening (O1) for drawing out a first pipe (P1) and a second pipe (P2) connecting the cascade heat exchanger and the first heat exchanger of the first circuit, and a liquid pipe (P3) and a gas pipe (P4) connecting the cascade heat exchanger and the second heat exchanger of the second circuit, is formed in a range from one end in a first direction to ⅓ of a first direction width; A wiring port (O2) for drawing out wiring connected to the electrical equipment is formed in a range from the other end in the first direction to 1 / 3 of the width in the first direction. Cascade unit.

2. The casing has a side surface (120a) extending in the first direction, The piping port and the wiring port are formed on the side surface. The cascade unit according to claim 1 .

3. The casing further has a bottom plate constituting a bottom surface (120f), The cascade heat exchanger is disposed near the piping port and on the bottom plate. A cascade unit according to claim 1 or 2.

4. The casing has a side surface (120a) extending in the first direction, When viewed from the side, the electrical equipment and the cascade heat exchanger do not overlap. A cascade unit according to any one of claims 1 to 3.

5. At the pipe port, the first pipe, the second pipe, the liquid pipe, and the gas pipe are arranged in a plurality of different directions. A cascade unit according to any one of claims 1 to 4.

6. The piping port and the wiring port are disposed at one end in a second direction perpendicular to the first direction, a maintenance opening is formed in the casing on the other end side in the second direction relative to the piping port and the wiring port; The casing further includes a removable plate member (120a1) that closes the opening. A cascade unit according to any one of claims 1 to 5.

7. The second refrigerant is carbon dioxide. A cascade unit according to any one of claims 1 to 6.

8. A cascade unit according to any one of claims 1 to 7; A first unit (5) including the first heat exchanger; A second unit (4a) including the second heat exchanger; Equipped with Refrigeration system.

Images