Refrigeration cycle device

Abstract

This refrigeration cycle device is provided with: a heat source machine having a compressor, a heat-source-side heat exchanger, and a first flow path switching device; a high-pressure-side pipe through which a refrigerant flows out from the heat source machine; a low-pressure-side pipe through which the refrigerant flows into and out from the heat source machine; a use-side unit; a heat medium relay unit; a first branch part; a second branch part; and an external heat source circuit that circulates the refrigerant between the heat source machine and the heat medium relay unit without passing the refrigerant through the first branch part and the second branch part. The first branch part is provided with a second flow path switching device that switches connection between a first connection pipe and the high-pressure-side pipe or the low-pressure-side pipe. The first flow path switching device is configured to form, when the heat-source-side heat exchanger functions as a condenser, such connection that the refrigerant flows from a discharge side of the compressor to the high-pressure-side pipe through the heat-source-side heat exchanger and such connection that the refrigerant flows from the low-pressure-side pipe to a suction side of the compressor and to form, when the heat-source-side heat exchanger functions as an evaporator, such connection that the refrigerant flows from the discharge side of the compressor to the high-pressure-side pipe and such connection that the refrigerant flows from the low-pressure-side pipe to the suction side of the compressor through the heat-source-side heat exchanger. The external heat source circuit is configured to be able to cause the refrigerant to flow between the discharge side or the suction side of the compressor and the heat-source-side heat exchanger via an inter-heat-medium heat exchanger.

Description

Refrigeration Cycle Equipment

[0001] The present disclosure relates to a refrigeration cycle device capable of multiple operations such as cooling operation, heating operation, and hot water supply operation, and in particular to a refrigeration cycle device that can reduce the load on a heat source-side heat exchanger by using unused heat as a heat source.

[0002] It has been known for some time that in combined air conditioning and hot water supply systems capable of simultaneously supplying cooling, heating, and hot water loads, balancing the cooling, heating, and hot water loads improves the system COP (see, for example, Patent Document 1). The refrigeration cycle device disclosed in Patent Document 1 includes a heat source unit, a relay unit connected to the heat source unit via a high-pressure connection pipe and a low-pressure connection pipe, and user units including an indoor unit and a hot water heat source circuit. The relay unit has a first distribution section and a second distribution section configured to selectively connect two connection pipes extending from each user unit to the high-pressure connection pipe or the low-pressure connection pipe. In Patent Document 1, the first distribution section switches the connection between one of the connection pipes of each user unit and the high-pressure connection pipe or the low-pressure connection pipe, allowing each user unit to individually perform heating operation, cooling operation, or hot water supply operation. The refrigeration cycle device of Patent Document 1 balances the cooling load, heating load, and hot water supply load of a plurality of user-side units, thereby improving the efficiency of the entire system.

[0003] Air conditioning systems that use melted snow water or well water are also known (see, for example, Patent Document 2). The snow and ice air conditioning system disclosed in Patent Document 2 includes an indirect outdoor air cooler, a compression refrigeration cooler, and a snow and ice cooler. The snow and ice cooler uses the cold energy of a snowy mountain to cool a refrigerant, which then cools the outdoor air supplied to the heat exchangers on the heat source side of the indirect outdoor air cooler and the compression refrigeration cooler. The snow and ice air conditioning system of Patent Document 2 makes effective use of the cold energy of a snowy mountain, enabling energy-saving operation.

[0004] Japanese Patent No. 5642085 Japanese Patent Application Laid-Open No. 2018-146221

[0005] The refrigeration cycle device disclosed in Patent Document 1 can improve COP by balancing the cooling load, heating load, and hot water supply load of the user unit, but the cooling / heating capacity required for the load in the usage situation of the user unit is borne by the heat source unit, so further energy-saving effects beyond the improvement of the COP of the refrigeration cycle device cannot be expected.

[0006] Furthermore, the snow and ice air conditioning system disclosed in Patent Document 2 can reduce the load on the indirect outdoor air cooler and the compression refrigeration cooler by using the cold energy from snowy mountains, but the refrigerant circuits of the indirect outdoor air cooler, the compression refrigeration cooler, and the snow and ice cooler are all independent. The snow and ice cooler supplies cooled outdoor air to the sensible heat exchanger of the indirect outdoor air cooler and the condenser of the compression refrigeration cooler, and the refrigerant circuits of the indirect outdoor air cooler and the compression refrigeration cooler are also independent, making it difficult to improve the efficiency of the entire system by balancing the loads of the two coolers.

[0007] The present disclosure has been made to solve the above-mentioned problems, and provides a refrigeration cycle device that improves COP by balancing the load between each user unit and enables energy-saving operation of the entire system by utilizing an external heat source.

[0008] a heat medium relay unit having an intermediate heat exchanger that exchanges heat between the refrigerant and a heat medium carrying heat from an external heat source and a second flow control device that controls the flow rate of the refrigerant flowing through the intermediate heat exchanger; a heat source unit having a compressor that compresses a refrigerant, a heat source side heat exchanger, and a first flow switching device that switches a flow rate of the refrigerant; a high-pressure side pipe through which the refrigerant flows out from the heat source unit; a low-pressure side pipe through which the refrigerant flows in and out of the heat source unit; a user side unit having a user side heat exchanger and a first flow control device that controls the flow rate of the refrigerant flowing through the user side heat exchanger; a heat medium relay unit having an intermediate heat exchanger that exchanges heat between the refrigerant and a heat medium carrying heat from an external heat source and a second flow control device that controls the flow rate of the refrigerant flowing through the intermediate heat exchanger; a first branch part that branches the high-pressure side pipe and the low-pressure side pipe to the user side unit, and connected to a first connecting pipe extending from the user side unit; a second branch part that branches the high-pressure side pipe and the low-pressure side pipe to the user side unit; and an external heat source circuit that circulates the refrigerant between a heat source unit and the heat medium relay unit, wherein the first branch section includes a second flow path switching device that switches a connection between the first connecting pipe and the high-pressure side pipe or the low-pressure side pipe, wherein the first flow path switching device is configured to connect the refrigerant so that it flows from a discharge side of the compressor via the heat source side heat exchanger to the high-pressure side pipe and from the low-pressure side pipe to the suction side of the compressor when the heat source side heat exchanger functions as a condenser, and to connect the refrigerant so that it flows from the discharge side of the compressor to the high-pressure side pipe and from the low-pressure side pipe to the suction side of the compressor via the heat source side heat exchanger when the heat source side heat exchanger functions as an evaporator, and the external heat source circuit is configured to allow the refrigerant to flow between the discharge side or the suction side of the compressor and the heat source side heat exchanger via the heat medium heat exchanger.

[0009] According to the present disclosure, a refrigeration cycle apparatus is configured so that a heat medium relay unit using an external heat source can be connected to a heat source unit via a relay unit, or the heat source unit and the heat medium relay unit can be directly connected via an external heat source circuit. Therefore, the refrigeration cycle apparatus can have the heat medium relay unit connected in series upstream or downstream of the heat source-side heat exchanger. This allows the refrigeration cycle apparatus to simultaneously perform simultaneous heating and cooling operations and hot water supply operations, and the heat medium relay unit can function to supplement or replace the capacity of the heat source-side heat exchanger. Furthermore, the heat medium relay unit can be appropriately used depending on the temperature of the external heat source, making it more efficient to use the heat medium relay unit as an auxiliary heat source. Because the heat medium relay unit can partially or entirely compensate for the capacity of the heat source-side heat exchanger using an external heat source, the refrigeration cycle apparatus can operate more energy-efficiently than conventional refrigeration cycle apparatuses.

[0010] 1 is a schematic diagram of a configuration of a refrigeration cycle apparatus 100 according to embodiment 1. FIG. 2 is an example of a circuit diagram showing the refrigeration cycle apparatus 100 according to embodiment 1. FIG. 3 is an explanatory diagram of a refrigerant flow when the refrigeration cycle apparatus 100 according to embodiment 1 is performing cooling operation. FIG. 4 is a Mollier diagram of the refrigeration cycle apparatus 100 according to embodiment 1 performing cooling operation. FIG. 5 is an explanatory diagram of a refrigerant flow when the refrigeration cycle apparatus 100 according to embodiment 1 is performing cooling operation. FIG. 6 is a Mollier diagram of the refrigeration cycle apparatus 100 according to embodiment 1 performing cooling operation. FIG. 7 is an explanatory diagram of a refrigerant flow when the refrigeration cycle apparatus 100 according to embodiment 1 is performing heating operation. FIG. 8 is a Mollier diagram of the refrigeration cycle apparatus 100 according to embodiment 1 performing heating operation. FIG. 9 is a Mollier diagram of the refrigeration cycle apparatus 100 according to embodiment 1 performing heating operation. FIG. 10 is an explanatory diagram of a refrigerant flow when the refrigeration cycle apparatus 100 according to embodiment 1 is performing defrost operation. FIG. 11 is a Mollier diagram of the refrigeration cycle apparatus 100 according to embodiment 1 performing defrost operation. 1 is an explanatory diagram of a refrigerant flow when the refrigeration cycle apparatus 100 according to Embodiment 1 is in defrost operation. FIG. 2 is a Mollier diagram of the refrigeration cycle apparatus 100 according to Embodiment 1 in defrost operation. FIG. 3 is an example of a circuit diagram showing a refrigeration cycle apparatus 200 according to Embodiment 2.

[0011] Embodiment 1. An embodiment of an air conditioning apparatus according to the present disclosure will now be described with reference to the drawings. FIG. 1 is a schematic diagram of the configuration of a refrigeration cycle apparatus 100 according to embodiment 1. As shown in FIG. 1, the refrigeration cycle apparatus 100 includes a heat source unit A, a relay unit B connected to the heat source unit A via a low-pressure side pipe 6 and a high-pressure side pipe 7, and a user unit C connected to the relay unit B via a first connection pipe 40 and a second connection pipe 41. The user unit C can select cooling operation, heating operation, or hot water supply operation by utilizing a refrigeration cycle. When the refrigeration cycle apparatus 100 includes multiple user units C, each of the multiple user units C can freely select and operate in one of the following operating modes: cooling operation, heating operation, or hot water supply operation. In other words, the refrigeration cycle apparatus 100 is capable of mixed cooling and heating operation, in which cooling operation and heating operation are performed simultaneously, as well as mixed operation such as water heating operation.

[0012] The heat source unit A and the relay unit B are connected by a low-pressure side pipe 6 and a high-pressure side pipe 7, and are configured so that refrigerant compressed by a compressor 1 (see Figure 2) provided in the heat source unit A is sent to the relay unit B, which then distributes the refrigerant to each user-side unit C. The operating state of each user-side unit C is changed depending on whether the first connection pipe 40 and the second connection pipe 41 are connected to the low-pressure side pipe 6 or the high-pressure side pipe 7. Figure 1 shows, as an example, a case where the top user-side unit C1 is in heating operation, the second user-side unit C2 from the top is in cooling operation, and the third user-side unit C3 from the top is in water-heating operation.

[0013] The user-side units C are, for example, indoor air conditioners or water heaters, which are supplied with refrigerant from the relay unit B and use a refrigeration cycle to perform indoor air conditioning or water heating. Each user-side unit C is connected in series to the relay unit B and in parallel with each other. In FIG. 1, three user-side units C are connected to the relay unit B, but this number is not limited, and two or more user-side units C may be installed, or even just one. Furthermore, the user-side unit C can be an indoor unit of an air conditioner, a water heater, a refrigerator, or the like, and there are no restrictions on the equipment that can be connected.

[0014] When the user-side unit C is directly connected to the low-pressure side pipe 6, the user-side heat exchanger 5 (see FIG. 2) functions as an evaporator and performs cooling operation, and when it is directly connected to the high-pressure side pipe 7, the user-side heat exchanger 5 functions as a condenser and performs heating operation or water-heating operation. The operation of each user-side unit C is switched by a second flow path switching device 10c (see FIG. 2) provided in the relay device B.

[0015] A heat medium converter D is also connected to the relay unit B. The heat medium converter D is connected to the relay unit B in a circuit configuration similar to that of the user unit C. Like the user unit C, the heat medium converter D is configured to allow a refrigerant to flow in from the relay unit B. The heat medium converter D is also connected to an external heat source E. The external heat source E and the heat medium converter D are connected by a circuit through which a heat medium different from the refrigerant flowing in from the relay unit B circulates. The heat medium converter D is configured to exchange heat between the heat medium having heat from the external heat source E and the refrigerant that flows into the heat medium converter D from the heat source unit A via the relay unit B, and to transfer heat or cold from the external heat source E to the refrigerant, thereby functioning as a condenser or evaporator. The heat medium converter D may be configured to circulate a liquid such as well water contained in the external heat source E through the heat medium circulation circuit 34 (see FIG. 2 ), or may be configured to circulate an independent heat medium through the heat medium circulation circuit 34.

[0016] In the first embodiment, the heat medium relay unit D functions to assist the heat source-side heat exchanger 3 (see FIG. 2 ) of the heat source unit A, and can function as a condenser when the heat source-side heat exchanger 3 functions as a condenser, and can function as an evaporator when the heat source-side heat exchanger 3 functions as an evaporator. This allows the heat source-side heat exchanger 3 to operate with reduced heat exchange capacity by the amount of use of the external heat source E, thereby achieving energy savings in the refrigeration cycle apparatus 100 as a whole.

[0017] Furthermore, the refrigeration cycle apparatus 100 is also capable of performing a defrosting operation of the heat source side heat exchanger 3 by utilizing the intermediate heat exchanger 30. This will be described later.

[0018] The external heat source E connected to the heat medium converter D is a source of heat or cold, such as well water, geothermal heat, or sunlight. The heat medium converter D is a device that transfers the heat or cold from the external heat source E to a refrigerant via a heat medium. When the external heat source E is well water, the well water is pumped up and circulated as a heat medium through a heat medium circulation circuit 34 (see FIG. 2 ). When geothermal heat is used as the external heat source E, a heat medium such as water heated by geothermal heat circulates through the heat medium circulation circuit 34. When sunlight is used as the external heat source E, a heat medium such as water heated by sunlight circulates through the heat medium circulation circuit 34. Alternatively, snow or melted snow may be used as the external heat source E. Alternatively, unused heat such as heat from river water, exhaust gas from equipment, wastewater, or waste heat generated by equipment may be used as the external heat source E. The heat medium such as water circulating through the heat medium circulation circuit 34 exchanges heat with the refrigerant circulating through the heat source unit A and the like in the intermediate heat exchanger 30 (see FIG. 2).

[0019] The heat medium relay unit D also includes an external heat source circuit 90 that is directly connected to the heat source unit A by piping without passing through the relay unit B. This allows the heat source unit A to utilize heat or cold from the external heat source E using the heat medium relay unit D. The refrigeration cycle apparatus 100 is capable of flowing refrigerant by directly connecting the compressor 1 and the intermediate heat exchanger 30. The intermediate heat exchanger 30 can be used as an auxiliary or alternative heat exchanger for the heat source side heat exchanger 3 that is used as a condenser or evaporator.

[0020] 1, one heat medium relay unit D and one external heat source E are installed, but a plurality of units may be installed. Also, the external heat source E may use a plurality of types of heat sources.

[0021] Whether the heat medium relay unit D is used as an evaporator or a condenser depends on whether the temperature of the external heat source E is high or low based on the evaporation temperature and condensation temperature of the refrigerant in the refrigeration cycle circulating through the heat source unit A, the relay unit B, the user unit C, and the heat medium relay unit D. When the temperature of the external heat source E is higher than the evaporation temperature of the refrigerant, the heat medium relay unit D is used as an evaporator, and when the temperature of the external heat source E is lower than the condensation temperature of the refrigerant, the heat medium relay unit D is used as a condenser. In general, when a relatively high-temperature external heat source E such as geothermal energy or sunlight is used, the heat medium relay unit D is used as an evaporator, and when a relatively low-temperature external heat source E such as well water, snow, or melted snow is used, the heat medium relay unit D is used as a condenser.

[0022] Depending on the temperature of the external heat source E, the heat medium relay unit D can be switched between using the first connection pipe 40 as an evaporator by directly connecting it to the low-pressure side pipe 6 and using it as a condenser by directly connecting it to the high-pressure side pipe 7. Switching of operation using the heat medium relay unit D is performed by the first flow switching device 2a and the third flow switching device 2b provided in the heat source unit A and the second flow switching device 10c (see FIG. 2 ) provided in the relay unit B. The first flow switching devices 2a and 2b provided in the heat source unit A may be collectively referred to as the heat source-side flow switching device 2.

[0023] (Circuit Configuration of Refrigeration Cycle Apparatus 100) Fig. 2 is an example of a circuit diagram showing the refrigeration cycle apparatus 100 according to Embodiment 1. The heat source unit A and the relay unit B are connected by a low-pressure side pipe 6 and a high-pressure side pipe 7. The high-pressure side pipe 7 is a pipe through which high-pressure refrigerant compressed by the compressor 1 flows out, either directly or via the heat source side heat exchanger 3. The low-pressure side pipe 6 is a pipe into which low-pressure refrigerant that has passed through the user side unit C or the heat medium relay unit D flows, and is a pipe through which the refrigerant is returned from the relay unit B to the heat source unit A. Note that the refrigeration cycle apparatus 100 shown in Figs. 1 and 2 has a relay unit B between the heat source unit A and the user side unit C and the heat medium relay unit D. However, the relay unit B does not need to be provided independently as long as the components constituting the refrigerant circuit, such as the first branch unit 10 of the relay unit B, are provided. For example, the first branch section 10, the second branch section 11, the gas-liquid separation device 12, the third flow control device 13, the fourth flow control device 14, the first heat exchanger 17 and the second heat exchanger 16 provided in the relay unit B may each exist independently or may be present within the heat source unit A or other unit.

[0024] The refrigerant in the high-pressure side pipe 7 flows into the high-pressure side branch 10a of the first branch 10 of the relay unit B. By opening the high-pressure side solenoid valves 9c1, 9c2, and 9d1 provided in the first branch 10, the refrigerant in the high-pressure side branch 10a flows into the user side unit C or the heat medium relay unit D. The high-pressure side solenoid valves 9c1, 9c2, and 9d1 may be collectively referred to as the high-pressure side solenoid valves 9.

[0025] The low-pressure side pipe 6 is connected to a low-pressure side branch 10b of the first branch 10 of the relay unit B. Refrigerant from the user side unit C or the heat medium relay unit D flows into the low-pressure side branch 10b by opening low-pressure side solenoid valves 8c1, 8c2, and 8d1. The low-pressure side solenoid valves 8c1, 8c2, and 8d1 may be collectively referred to as low-pressure side solenoid valves 8.

[0026] The low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 are respectively connected to first connection pipes 40c1, 40c2, and 40d1, which are one of the pipes extending from the user side unit C and the heat medium relay unit D. The first connection pipes 40c1, 40c2, and 40d1 may be collectively referred to as the first connection pipes 40.

[0027] The other pipes extending from the user side unit C and the heat medium relay unit D are referred to as second connection pipes 41c1, 41c2, and 41d1. The second connection pipes 41c1, 41c2, and 41d1 are connected to the second branch section 11 of the relay unit. The second connection pipes 41c1, 41c2, and 41d1 may be collectively referred to as second connection pipes 41.

[0028] By switching the low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 of the first branch section 10 between open and closed states, the refrigerant can be switched between flowing into the user-side unit C and the heat medium converter D from the second branch section 11 and flowing out from the user-side unit C and the heat medium converter D to the second branch section 11.

[0029] For example, when the high-pressure side solenoid valve 9 is open and the low-pressure side solenoid valve 8 is closed, the refrigerant flows from the high-pressure side branch 10a connected to the high-pressure side pipe 7 through the high-pressure side solenoid valve 9 into the user side unit C or the heat medium relay unit D, and the refrigerant that has passed through the user side unit C or the heat medium relay unit D flows into the second branch 11.

[0030] For example, when the high-pressure side solenoid valve 9 is closed and the low-pressure side solenoid valve 8 is opened, refrigerant that has passed through another user-side unit C, another heat medium relay unit D, or refrigerant that has been separated from the high-pressure side piping 7 by the gas-liquid separator 12 and passed through the first heat exchanger 17 and the second heat exchanger 16 flows from the second branch 11 into the user-side unit C or the heat medium relay unit D. The refrigerant that has passed through the user-side unit C or the heat medium relay unit D passes through the low-pressure side solenoid valve 8 and flows from the low-pressure side branch 10b into the low-pressure side piping 6. The first heat exchanger 17 and the second heat exchanger 16 are sometimes referred to as internal heat exchangers.

[0031] As described above, the relay unit B switches the connection state of the user unit C or the relay unit D by switching the open / close states of the low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 of the first branch section 10. This switching switches whether the user-side heat exchanger 5 of the user unit C and the intermediate heat exchanger 30 of the relay unit D function as an evaporator or a condenser, respectively.

[0032] The first branching section 10 branches the high-pressure side pipe 7 and the low-pressure side pipe 6 for each of the user units C and the heat medium relay units D, and connects them to a first connecting pipe 40, which is one of the pipes extending from each of the user units C and the heat medium relay units D. The first branching section 10 controls whether the first connecting pipes 40 of the user units C and the heat medium relay units D are connected to the high-pressure side pipe 7 or the low-pressure side pipe 6 by closing one of the high-pressure side solenoid valve 9 and the low-pressure side solenoid valve 8 and opening the other. The low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 of the first branching section 10 are sometimes collectively referred to as a second flow path switching device 10c. The second flow path switching device 10c includes a high-pressure side solenoid valve 9 and a low-pressure side solenoid valve 8, respectively, but is not limited to this configuration. For example, the second flow path switching device 10c may be configured as a three-way valve to which the high-pressure side pipe 7, the low-pressure side pipe, and the first connecting pipe 40 are connected.

[0033] (Heat source unit A) The heat source unit A is usually placed in a space outside a building such as a rooftop, and supplies cold or hot heat to the user side units C1 and C2 via the relay unit B. The heat source unit A is not limited to being placed outdoors, and may be placed in an enclosed space such as a machine room with a ventilation opening. The heat source unit A may also be placed inside a building if waste heat can be exhausted to the outside of the building through an exhaust duct. Furthermore, the heat source unit A may be placed inside a building as a water-cooled outdoor unit.

[0034] The heat source unit A incorporates a compressor 1, a first flow switching device 2a that switches the refrigerant flow direction of the heat source unit A, a heat source side heat exchanger 3, and an accumulator 29. The compressor 1, the first flow switching device 2a, the heat source side heat exchanger 3, and the accumulator 29 are connected by a low pressure side pipe 6 and a high pressure side pipe 7.

[0035] The heat source side heat exchanger 3 is connected in series with the first flow rate control device 22. Furthermore, in the heat source unit A, a bypass pipe 25 having a second flow rate control device 26 is connected in parallel with the heat source side heat exchanger 3. The second flow rate control device 26 adjusts the flow rate to adjust the amount of refrigerant that bypasses the heat source side heat exchanger 3. In Fig. 3, the bypass pipe 25 is directly connected to the discharge side of the compressor 1, but it may also be connected between the first flow rate switching device 2a and the third flow rate switching device 2b.

[0036] An outdoor flow control device 3m is installed near the heat source-side heat exchanger 3 to control the flow rate of a fluid, such as outdoor air. In the first embodiment, the outdoor air is sent to the heat source-side heat exchanger 3 by the outdoor flow control device 3m, where it exchanges heat with the refrigerant. The outdoor flow control device 3m is, for example, a fan that sends the outdoor air to the heat source-side heat exchanger 3. In the first embodiment, an air-cooled outdoor heat exchanger is used as an example of the heat source-side heat exchanger 3, and an outdoor fan is used as an example of the outdoor flow control device 3m. The heat source-side heat exchanger 3 may be a water-cooled outdoor heat exchanger or the like, as long as it exchanges heat between the refrigerant and another fluid. In this case, a pump is used as the outdoor flow control device 3m. A heat medium, such as outdoor air, that exchanges heat with the refrigerant in the heat source-side heat exchanger 3 may be referred to as a heat source heat medium. Although the first embodiment illustrates an example in which one heat source-side heat exchanger 3 is provided, multiple heat source-side heat exchangers may be provided.

[0037] Furthermore, the heat source unit A is provided with a first connecting pipe 60a, a second connecting pipe 60b, a check valve 18, a check valve 19, a check valve 20, and a check valve 21. Regardless of the connection direction of the first flow path switching device 2a, the first connecting pipe 60a, the second connecting pipe 60b, the check valve 18, the check valve 19, the check valve 20, and the check valve 21 allow high-pressure refrigerant to flow from inside the heat source unit A to the relay unit B via the high-pressure side pipe 7. Furthermore, the first connecting pipe 60a, the second connecting pipe 60b, the check valve 18, the check valve 19, the check valve 20, and the check valve 21 allow low-pressure refrigerant from the relay unit B to flow into the heat source unit A via the low-pressure side pipe 6.

[0038] The compressor 1 draws in a refrigerant and compresses it to a high-temperature and high-pressure state, and is configured, for example, by a capacity-controllable inverter compressor.

[0039] The first flow switching device 2a switches the refrigerant flow between heating operation and cooling operation. The first flow switching device 2a switches between two connection states. In one connection state, the first pipe 27 and the bypass pipe 25 are connected to the discharge side of the compressor 1, and the low-pressure side pipe 6 is connected to an accumulator 29 provided on the suction side of the compressor 1. The first pipe 27 is installed in parallel with the bypass pipe 25 and is a pipe leading to the heat source side heat exchanger 3. In the other connection state, the first pipe 27 and the bypass pipe 25 are connected to the accumulator 29 provided on the suction side of the compressor 1, and the discharge side of the compressor 1 is directly connected to the high-pressure side pipe 7. In FIG. 2 , a third flow switching device 2b is connected between the first flow switching device 2a and the first pipe 27 leading to the heat source side heat exchanger 3. The third flow switching device 2b is intended to enable direct connection between the heat source unit A and the heat medium relay unit D via the external heat source circuit 90. The third flow switching device 2b can switch between connection and disconnection between the heat source unit A and the heat medium relay unit D. The third flow switching device 2b and the external heat source circuit 90 will be described later.

[0040] The first flow path switching device 2 a is illustrated as a four-way switching valve. By switching the flow path of the first flow path switching device 2 a, the heat source side heat exchanger 3 functions as an evaporator during heating operation and as a condenser or a radiator during cooling operation.

[0041] In the first embodiment, the heat source-side heat exchanger 3 exchanges heat between the refrigerant and outdoor air, evaporating the refrigerant to gasify it or condensing it to liquefy it. The outdoor flow rate control device 3m forms an air path for the air flowing to the heat source-side heat exchanger 3. The accumulator 29 is provided on the suction side of the compressor 1 and stores surplus refrigerant due to differences between heating and cooling operations or surplus refrigerant due to transient changes in operation. Although the first embodiment illustrates the case where one heat source-side heat exchanger 3 is provided, multiple heat source-side heat exchangers 3 may be connected in parallel.

[0042] The check valve 18 is connected to the high-pressure side pipe 7 between the heat source side heat exchanger 3 and the relay unit B, and allows refrigerant to flow only in the direction from the heat source unit A to the relay unit B. The check valve 19 is provided in the low-pressure side pipe 6 between the relay unit B and the first flow path switching device 2a, and allows refrigerant to flow only in the direction from the relay unit B to the heat source unit A. The check valve 20 is provided in the first connecting pipe 60a, and allows refrigerant discharged from the compressor 1 to flow to the relay unit B during heating operation. The check valve 21 is provided in the second connecting pipe 60b, and allows refrigerant returning from the relay unit B to flow to the suction side of the compressor 1 via the heat source side heat exchanger 3 or the bypass pipe 25 during heating operation.

[0043] The first connection pipe 60a connects, within the heat source unit A, the low-pressure side pipe 6 between the first flow path switching device 2a and the check valve 19, and the high-pressure side pipe 7 between the check valve 18 and the relay unit B. The second connection pipe 60b connects, within the heat source unit A, the low-pressure side pipe 6 between the check valve 19 and the relay unit B, and the high-pressure side pipe 7 between the heat source-side heat exchanger 3 and the check valve 18.

[0044] The heat source unit A may also be provided with a discharge pressure gauge 51, a suction pressure gauge 52, an intermediate-pressure pressure gauge 53, and a thermometer 54. The discharge pressure gauge 51 is provided on the discharge side of the compressor 1 and measures the pressure of the refrigerant discharged from the compressor 1. The suction pressure gauge 52 is provided on the suction side of the compressor 1 and measures the pressure of the refrigerant sucked into the compressor 1. The intermediate-pressure pressure gauge 53 is provided upstream of the check valve 18 and measures the intermediate pressure, which is the pressure of the refrigerant upstream of the check valve 18. The thermometer 54 is provided on the discharge side of the compressor 1 and measures the temperature of the refrigerant discharged from the compressor 1. Pressure information and temperature information detected by the discharge pressure gauge 51, the suction pressure gauge 52, the intermediate-pressure pressure gauge 53, and the thermometer 54 are sent to the control device 50 that controls the operation of the refrigeration cycle apparatus 100, and are used to control the actuators.

[0045] The first flow rate control device 22 is connected in series to the heat source side heat exchanger 3, and is provided between the check valves 21 and 18 and the heat source side heat exchanger 3, and is configured to be able to open and close freely. The first flow rate control device 22 adjusts the flow rate of refrigerant flowing from the heat source side heat exchanger 3 to the check valve 18 during cooling operation, and adjusts the flow rate of refrigerant flowing from the check valve 21 into the heat source side heat exchanger 3 during heating operation. The first flow rate control device 22 is configured so that the flow path resistance changes continuously.

[0046] The bypass pipe 25 bypasses the heat source-side heat exchanger 3. The second flow control device 26 is provided midway along the bypass pipe 25, is configured to be freely openable and closable, and controls the flow rate of the refrigerant flowing through the bypass pipe 25. The second flow control device 26 adjusts the flow rate of the refrigerant flowing into the heat source-side heat exchanger 3. The second flow control device 26 is configured so that the flow path resistance changes continuously.

[0047] (Relay unit B) The relay unit B incorporates a first branch section 10, a second branch section 11, a gas-liquid separator 12, a first bypass pipe 14a, a second bypass pipe 14b, a third flow control device 13, a fourth flow control device 15, a first heat exchanger 17, a second heat exchanger 16, and a control device 50. The control device 50 has the same configuration and function as the control device 50 of the heat source unit A.

[0048] The first branch section 10 branches the refrigerant flowing through the high-pressure side pipe 7 toward the user unit C and the heat medium relay unit D. The first branch section 10 also merges the refrigerant flowing through the user unit C and the heat medium relay unit D and causes the refrigerant to flow into the low-pressure side pipe 6. The first branch section 10 includes a low-pressure side solenoid valve 8 and a high-pressure side solenoid valve 9 installed on first connecting pipes 40 of the user unit C and the heat medium relay unit D. In other words, the first connecting pipes 40 of the user unit C and the heat medium relay unit D are branched at the first branch section 10, one branch connected to the low-pressure side pipe 6 via the low-pressure side solenoid valve 8 and the other branch connected to the high-pressure side pipe 7 via the high-pressure side solenoid valve 9.

[0049] The low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 are controlled to open and close, thereby switching the first connecting pipe 40 of the user side unit C and the heat medium relay unit D to either the low-pressure side pipe 6 or the high-pressure side pipe 7. The low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 provided in the relay unit B are collectively referred to as a second flow path switching device 10c. The low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 are installed on each of the two pipes where the first connecting pipe 40 branches, but they may also be configured using, for example, a three-way valve. That is, other structures may be used as long as the first connecting pipe 40 of the user side unit C and the heat medium relay unit D is configured to connect to either the low-pressure side pipe 6 or the high-pressure side pipe 7. The low-pressure side solenoid valve 8 and the high-pressure side solenoid valve 9 are preferably configured to be closed to prevent refrigerant from flowing through any of the user side units C and the heat medium relay units D.

[0050] The second branch section 11 branches the refrigerant flowing through the first bypass pipe 14a toward the user unit C and the heat medium relay unit D. The second branch section 11 also merges the refrigerant flowing through the user unit C and the heat medium relay unit D and causes the refrigerant to flow into the second bypass pipe 14b. The second branch section 11 has a junction where the first bypass pipe 14a and the second bypass pipe 14b meet.

[0051] The gas-liquid separator 12 is provided midway along the high-pressure side pipe 7, and separates the refrigerant that has flowed in through the high-pressure side pipe 7 into gas and liquid. The gas phase portion separated by the gas-liquid separator 12 flows to the first branch section 10, and the liquid phase portion separated by the gas-liquid separator 12 flows to the second branch section 11.

[0052] The first bypass pipe 14a is a pipe that connects the gas-liquid separator 12 and the second branch 11 in the relay unit B. The second bypass pipe 14b is a pipe that connects the second branch 11 and the low-pressure side pipe 6 in the relay unit B. The third flow control device 13 is provided midway along the first bypass pipe 14a and is configured to be able to open and close freely. The fourth flow control device 15 is provided midway along the second bypass pipe 14b and is configured to be able to open and close freely.

[0053] The first heat exchanger 17 exchanges heat between the refrigerant in the first bypass pipe 14a between the gas-liquid separator 12 and the third flow control device 13 and the refrigerant in the second bypass pipe 14b between the fourth flow control device 15 and the low-pressure side pipe 6. The second heat exchanger 16 exchanges heat between the refrigerant in the first bypass pipe 14a between the third flow control device 13 and the second branch portion 11 and the refrigerant in the second bypass pipe 14b between the fourth flow control device 15 and the first heat exchanger 17.

[0054] (User-side unit C) The user-side units C are installed in positions where they can supply conditioned air to a space to be air-conditioned, such as a room, and supply cooled air or heated air to the space to be air-conditioned using cold or hot heat from the heat source unit A supplied via the relay unit B. The user-side units C1 and C2 each have a built-in user-side heat exchanger 5c1 or 5c2 and a first flow control device 4c1 or 4c2.

[0055] In addition, a flow control device 5m is installed near the user-side heat exchangers 5c1, 5c2 to control the flow rate of indoor air, which is a fluid that exchanges heat with the refrigerant. In the first embodiment, air-cooled user-side heat exchangers are used as an example of the user-side heat exchangers 5c1, 5c2, and an indoor fan is used as an example of the flow control device 5m. However, a water-cooled user-side heat exchanger or the like may also be used as long as the refrigerant exchanges heat with another fluid. Furthermore, if a water heater is used as the user-side unit C, the user-side heat exchanger 5 may be a water heat exchanger that exchanges heat between water and the refrigerant. In this case, a pump that moves water is used as the flow control device 5m.

[0056] Each of the use-side heat exchangers 5c1 and 5c2 exchanges heat between the air supplied from the flow control device 5m and the refrigerant to generate heated air or cooled air to be supplied to the air-conditioned space. The flow control device 5m forms an air path for the air flowing to the use-side heat exchangers 5c1 and 5c2. The first flow control devices 4c1 and 4c2 are provided between the second branching section 11 of the relay unit B and the use-side heat exchanger 5c1 or 5c2 and are configured to be able to open and close freely. The first flow control devices 4c1 and 4c2 adjust the flow rates of the refrigerant flowing into the use-side heat exchangers 5c1 and 5c2.

[0057] (Relay Unit D) The relay unit D supplies heat or cold from the external heat source E to the refrigerant circulating in the refrigeration cycle apparatus 100. The relay unit D has an intermediate heat exchanger 30 that exchanges heat between the refrigerant circulating in the heat source unit A, the relay unit B, and the user unit C and a heat medium that carries heat from the external heat source E. The relay unit D also has a built-in second flow control device 4d1 that controls the flow rate of the refrigerant circulating in the intermediate heat exchanger 30. The second flow control device 4d1 is provided between the second branch unit 11 of the relay unit B and the intermediate heat exchanger 30d1 and is configured to be freely openable and closable. The second flow control device 4d1 adjusts the flow rate of the refrigerant flowing into the intermediate heat exchanger 30d1.

[0058] The heat medium is circulated through the heat medium circulation circuit 34 by the pump 31 and sent from the external heat source E to the intermediate heat exchanger 30. The intermediate heat exchanger 30 is, for example, a plate-type heat exchanger, and the refrigerant and the heat medium circulate inside, and the heat or cold of the heat medium is transferred to the refrigerant.

[0059] The heat medium relay unit D includes external heat source temperature sensors 32 and 33. The external heat source temperature sensor 32 detects the temperature of the heat medium flowing into the intermediate heat exchanger 30. The external heat source temperature sensor 33 detects the temperature of the heat medium flowing out of the intermediate heat exchanger 30.

[0060] (External Heat Source E) The external heat source E is, for example, well water, melted snow, ice and snow, geothermal energy, solar light, etc., and the heat medium can be changed appropriately depending on the target heat source. For example, if the external heat source E is well water stored in large quantities in an underground well, the well water is pumped up by a pump 31 to serve as a heat medium and is then introduced into the intermediate heat exchanger 30 by the heat medium circulation circuit 34. The well water exchanges heat with the refrigerant, flows out of the intermediate heat exchanger 30, and its temperature increases. The well water with its increased temperature is returned to the well. The well water that serves as the external heat source E is stored in large quantities underground, and even if the water with its increased temperature is returned through the heat medium converter D, the temperature of the external heat source E remains almost unchanged.

[0061] The heat medium circulation circuit 34 may be configured to circulate an independent heat medium therein. As shown in FIG. 2 , the heat medium circulation circuit 34 may be connected to an external heat exchanger F that exchanges heat between an external heat source E and the heat medium flowing through the heat medium circulation circuit 34. The external heat exchanger F exchanges heat between the heat medium and the external heat source E. The heat medium that has exchanged heat in the external heat exchanger F is sent to the heat medium-to-heat medium heat exchanger 30 and exchanges heat with the refrigerant circulating through the refrigeration cycle apparatus 100. This configuration maintains the quality of the heat medium flowing through the heat medium circulation circuit 34, and ensures the durability of the heat medium circulation circuit 34 and the heat medium converter D, compared to, for example, pumping well water as the heat medium. The configuration of the heat medium circulation circuit 34 may be changed as appropriate depending on the external heat source E.

[0062] Furthermore, when geothermal energy is used as the external heat source E, piping through which a heat medium such as water circulates is extended underground to transfer the geothermal energy to the heat medium. When sunlight is used as the external heat source E, piping through which a heat medium such as water circulates is connected to a solar water heater or the like to transfer heat from the sunlight to the heat medium. The refrigeration cycle apparatus 100 according to the first embodiment effectively utilizes such an external heat source E to achieve energy savings.

[0063] (Control device 50) The refrigeration cycle apparatus 100 is provided with a control device 50. The control device 50 controls actuators and the like based on refrigerant pressure information, refrigerant and heat medium temperature information, outdoor temperature information, indoor temperature information, and the like detected by each sensor provided in the refrigeration cycle apparatus 100. For example, the control device 50 controls driving of the compressor 1, switching between the first flow path switching device 2a and the second flow path switching device 10c, driving of the fan motor of the outdoor flow control device 3m, driving of the fan motor of the flow control device 5m, and the pump 31 that sends the heat medium to the heat source side heat exchanger 3.

[0064] The control device 50 controls the opening degrees of the first flow control device 22, the second flow control device 26, the third flow control device 13, and the fourth flow control device 15. The control device 50 includes a memory 50a that stores information for determining each control value. The control device 50 may be configured with hardware such as a control circuit that realizes its functions. The control device 50 may also be configured with a software program stored in a storage unit such as a semiconductor memory and a computing device such as a microcomputer or CPU (Central Processing Unit) that executes the software program. Although the first embodiment illustrates a case in which the control device 50 is provided in the heat source unit A and the relay unit B, the number of control devices 50 may be one or three or more. The control device 50 may also be installed in the user unit C or the heat medium relay unit D, or may be installed as a separate unit in a location other than the heat source unit A, the relay unit B, the user unit C, and the heat medium relay unit D.

[0065] 1 and 2, the heat source unit A and the heat medium reactor D are configured so that the refrigerant flowing out from the heat source unit A is sent directly to the heat medium reactor D via the external heat source circuit 90, and heat exchange occurs between the refrigerant and a heat medium having heat or cold from the external heat source E1. The refrigerant that has exchanged heat with the external heat source E1 returns to the heat source unit A and is used in the user unit C as described above, or is drawn into the compressor 1 and is pressurized and heated again.

[0066] In the heat source unit A, a third flow switching device 2b is connected between the first flow switching device 2a and a first pipe 27 connected to the heat source side heat exchanger 3. The third flow switching device 2b switches between two connection states. In one connection state, the first flow switching device 2a is connected to the first pipe 27 connected to the heat source side heat exchanger 3. In the other connection state, the first flow switching device 2a is connected to the heat source side heat exchanger 3. By switching these connection states, the third flow switching device 2b circulates or blocks the refrigerant between the heat source unit A and the heat medium relay unit D.

[0067] When refrigerant is circulated between the heat source unit A and the heat medium relay unit D via the external heat source circuit 90, the second flow switching device 10c of the relay unit B cuts off the connection between the first branch unit 10 and the heat medium relay unit D. In other words, at this time, refrigerant is not circulated between the relay unit B and the heat medium relay unit D.

[0068] One pipe 91 of the external heat source circuit 90 connects the third flow switching device 2b and the second connection pipe 41d1. The other pipe 92 of the external heat source circuit 90 connects the first connection pipe 40d1 and the third flow switching device 2b. An on-off valve 93 is installed in one pipe 91. The on-off valve 93 closes when refrigerant is not flowing through the external heat source circuit 90, preventing refrigerant that has flowed into the heat medium relay unit D via the relay unit B from flowing into the external heat source circuit 90. The installation location of the on-off valve 93 is not limited as long as it prevents refrigerant from flowing through the external heat source circuit 90.

[0069] (Operation modes of the refrigeration cycle apparatus 100) Next, the operating behavior during various operations performed by the refrigeration cycle apparatus 100 will be described. The operating behavior of the refrigeration cycle apparatus 100 includes cooling operation, heating operation, and defrost operation. The cooling operation includes cooling-dominated operation in which heating operation is performed in some of the use-side units C. The heating operation includes heating-dominated operation in which cooling operation is performed in some of the use-side units C. The defrost operation includes operation in which the use-side units C are stopped and the heat-source-side heat exchanger 3 is defrosted, and operation in which defrosting is performed while the use-side units C are operating.

[0070] Cooling operation is an operation mode in which all of the user-side units C are in either cooling operation or stopped. Heating operation is an operation mode in which all of the user-side units C are in either heating operation or stopped. Cooling-dominated operation is an operation mode in which cooling or heating can be selected for each indoor unit, and the cooling load is greater than the heating load. Cooling-dominated operation is an operation mode in which the heat-source-side heat exchanger 3 is connected to the discharge side of the compressor 1 and acts as a condenser. Heating-dominated operation is an operation mode in which heating or cooling can be selected for each indoor unit, and the heating load is greater than the cooling load. Heating-dominated operation is an operation mode in which the heat-source-side heat exchanger 3 is connected to the suction side of the compressor 1 and acts as an evaporator.

[0071]

[0072] Table 1 shows the operation of the refrigeration cycle apparatus 100 according to the first embodiment in each operation mode. The control device 50 operates the first flow switching device 2a, the second flow switching device 10c, and the third flow switching device 2b to determine how the refrigerant flows into the relay unit D. The intermediate heat exchanger 30 of the relay unit D basically functions to assist the heat source side heat exchanger 3. Therefore, it functions as an evaporator when the heat source side heat exchanger 3 is an evaporator, and as a condenser when the heat source side heat exchanger 3 is a condenser. However, whether the refrigerant flows first through the intermediate heat exchanger 30 or the heat source side heat exchanger 3 is determined depending on the relationship between the outside air temperature T, the external heat source temperature t, and the freezing threshold temperature f of the intermediate heat exchanger 30, which perform heat exchange with the heat source side heat exchanger 3.

[0073] (Operating Condition No. 1: Cooling Operation) FIG. 3 is an explanatory diagram of the refrigerant flow when the refrigeration cycle apparatus 100 according to Embodiment 1 is operating in cooling mode. FIG. 3 shows the state of the refrigeration cycle apparatus 100 under operating condition No. 1 in Table 1. Operating condition No. 1 corresponds to a case in which the outside air temperature T is higher than the external heat source temperature t. The refrigerant discharged from the compressor 1 is condensed in the heat-source-side heat exchanger 3 and then in the intermediate heat exchanger 30. This condenses the refrigerant to a temperature equivalent to the lower temperature of the external heat source E1, ensuring an enthalpy difference between the refrigerant before and after passing through the condenser, thereby further improving the cooling capacity. The outside air temperature T is the temperature of the air flowing into the heat-source-side heat exchanger 3 and is measured by the temperature sensor 3t. The external heat source temperature t is measured by the external heat source temperature sensor 33 installed on the outlet side of the intermediate heat exchanger 30d1 in the heat medium circulation circuit 34 of the heat medium relay unit D1. However, the external heat source temperature t may be a value measured by an external heat source temperature sensor 32 installed on the inlet side of the heat medium-related heat exchanger 30d1, or the temperature of the external heat source E itself may be measured and used.

[0074] 3 illustrates a cooling operation in which both the user-side units C1 and C2 are in cooling mode. When the cooling operation is performed, the control device 50 switches the first flow path switching device 2a so that the refrigerant discharged from the compressor 1 flows to the heat-source-side heat exchanger 3. The low-pressure-side solenoid valves 8c1 and 8c2 connected to the user-side units C1 and C2 are opened, and the high-pressure-side solenoid valves 9c1 and 9c2 are closed. In Figure 3 and subsequent figures, the closed valves of the second flow path switching device 10c are indicated by solid black.

[0075] When the compressor 1 starts operating, a low-temperature, low-pressure gaseous refrigerant is compressed by the compressor 1 and discharged as a high-temperature, high-pressure gaseous refrigerant. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1 flows into the heat-source-side heat exchanger 3 via the first flow switching device 2a. The third flow switching device 2b is switched to connect the first flow switching device 2a and the heat-source-side heat exchanger 3, and the external heat source circuit 90 is blocked. The refrigerant discharged from the compressor 1 and flowing into the heat-source-side heat exchanger 3 is cooled while heating the outdoor air, and becomes a medium-temperature, high-pressure liquid refrigerant or a gas-liquid two-phase refrigerant. The medium-temperature, high-pressure refrigerant flowing out of the heat-source-side heat exchanger 3 passes through the high-pressure-side pipe 7 and is separated into a liquid refrigerant and a gas-liquid refrigerant by the gas-liquid separator 12.

[0076] The liquid refrigerant separated by the gas-liquid separator 12 passes through the first bypass pipe 14a, exchanges heat with the refrigerant flowing through the second bypass pipe 14b in the first heat exchanger 17, then passes through the third flow control device 13, exchanges heat with the refrigerant flowing through the second bypass pipe 14b in the second heat exchanger 16, is cooled, and flows into the second branch section 11.

[0077] A portion of the refrigerant that flows into the second branch 11 is bypassed to the second bypass piping 14b, and the remainder flows into the second connecting piping 41c1, 41c2 of the user-side units C1, C2. The high-pressure liquid or two-phase gas-liquid refrigerant branched at the second branch 11 flows through the second connecting piping 41c1, 41c2 and flows into the first flow control devices 4c1, 4c2 of the user-side units C1, C2. The high-pressure liquid refrigerant is then throttled and expanded by the first flow control devices 4c1, 4c2, reducing its pressure and becoming a low-temperature, low-pressure, two-phase gas-liquid refrigerant. The low-temperature, low-pressure, two-phase gas-liquid refrigerant that flows out of the first flow control devices 4c1, 4c2 flows into the user-side heat exchangers 5c1, 5c2. The refrigerant is then heated while cooling the indoor air, becoming a low-temperature, low-pressure, gaseous refrigerant.

[0078] The low-temperature, low-pressure gaseous refrigerant flowing out from the user-side heat exchangers 5c1, 5c2 passes through the low-pressure-side solenoid valves 8c1, 8c2, respectively, and flows into the low-pressure-side branch 10b of the first branch 10. The low-temperature, low-pressure gaseous refrigerant that joins in the low-pressure-side branch 10b also joins with the low-temperature, low-pressure gaseous refrigerant that has been heated in the first heat exchanger 17 and the second heat exchanger 16 of the second bypass pipe 14b, passes through the low-pressure-side pipe 6 and the first flow switching device 2a, flows into the compressor 1, and is compressed.

[0079] When the heat medium relay unit D1 is connected to the refrigeration cycle apparatus 100, it is determined whether to connect the heat medium relay unit D1 upstream or downstream of the heat source-side heat exchanger 3 based on the magnitude relationship between the temperature t of the external heat source E1 and the temperature T of the heat flowing into the heat source-side heat exchanger 3.

[0080] The outside air temperature T is the temperature of the outside air sent to the heat source-side heat exchanger 3, and the external heat source temperature t is the temperature of the heat medium circulating through the heat medium circuit 34. In particular, temperature t1 is the temperature of the heat medium flowing into the intermediate heat exchanger 30d1 of the heat medium relay unit D1, and temperature t2 is the temperature of the heat medium flowing into the intermediate heat exchanger 30d2 of the heat medium relay unit D2. The cooling operation shown in FIG. 3 illustrates a case where the heat medium temperature t is lower than the outside air temperature T flowing into the heat source-side heat exchanger 3. In the first embodiment, the temperature t2 of the refrigerant flowing out of the intermediate heat exchanger 30d1 is used as the external heat source temperature t. The temperature T is measured by a temperature sensor 3t installed near the heat source-side heat exchanger 3. The temperature t1 is measured by an external heat source temperature sensor 32 installed upstream of the intermediate heat exchanger 30d1 in the heat medium circuit 34 of the heat medium relay unit D1. The temperature t2 is measured by an external heat source temperature sensor 32 installed upstream of the intermediate heat exchanger 30d2 in the heat medium circulation circuit 34 of the heat medium relay unit D2.

[0081] The medium-temperature, high-pressure liquid refrigerant flowing out of the heat source-side heat exchanger 3 passes through the high-pressure-side pipe 7 and is separated into liquid refrigerant and gas refrigerant in the gas-liquid separator 12. The separated gas refrigerant flows into the high-pressure-side branch 10a. The high-pressure-side solenoid valve 9d1 connected to the heat medium relay unit D1 is opened, and the low-pressure-side solenoid valve 8d1 is closed. The gas refrigerant in the high-pressure-side branch 10a flows through the first connecting pipe 40d1 and into the intermediate heat exchanger 30d1.

[0082] The gas refrigerant that flows into the heat medium-intermediate heat exchanger 30d1 is condensed by heat exchange with the low-temperature heat medium, becoming a high-pressure, low-temperature liquid or gas-liquid two-phase refrigerant. The high-pressure, low-temperature refrigerant is throttled by the second flow control device 4d1, expands, and reduces its pressure, becoming a low-temperature, low-pressure, gas-liquid two-phase refrigerant. The refrigerant that flows out of the second flow control device 4d1 flows into the second branch section 11, where it is mixed with the refrigerant that flows into the second branch section 11 from the gas-liquid separator 12 via the first bypass pipe 14a, and then flows into the user-side units C1 and C2.

[0083] As described above, during cooling operation of the refrigeration cycle apparatus 100, not only the heat source-side heat exchanger 3 but also the heat medium relay unit D1 can be used as a condenser. Therefore, in the heat source unit A, the output of the outdoor flow control device 3m that sends air to the heat source-side heat exchanger 3 can be reduced, or part of the refrigerant discharged from the compressor 1 can be sent from the bypass piping 25 to the high-pressure piping 7. The refrigerant that passes through the bypass piping 25 without passing through the heat source-side heat exchanger 3 flows from the gas-liquid separator 12 into the high-pressure branch section 10a and into the intermediate heat exchanger 30d1 where it is condensed. In this way, the heat medium relay unit D1 can supplement the capacity of the heat source-side heat exchanger 3 by utilizing the external heat source E1.

[0084] Depending on the capacity of the heat medium relay unit D1, the heat source unit A may be configured so that the refrigerant does not flow into the heat source-side heat exchanger 3 and all of the refrigerant flows through the bypass pipe 25 to the high-pressure-side pipe 7. The high-pressure refrigerant is separated into liquid refrigerant and gas refrigerant in the gas-liquid separator 12. The gas refrigerant flows into the heat medium relay unit D1 through the high-pressure-side branch 10a, where it exchanges heat with the heat medium and is condensed. The low-temperature, high-pressure liquid or gas-liquid two-phase refrigerant is then decompressed by the flow control devices 4d1, 4c1, and 4c2 and flows into the user-side heat exchangers 5c1 and 5c2, where it exchanges heat with the indoor air and expands, thereby cooling the room. In this way, the heat medium relay unit D1 can function as a substitute for the heat source-side heat exchanger 3 by utilizing the external heat source E1.

[0085] In the cooling operation of No. 1 in Table 1, the temperature t of the heat medium circulating through the heat medium relay unit D1 is low, so the control device 50 may control the flow rate of the pump 31 of the heat medium relay unit D1 to be increased. This allows more cold heat from the external heat source E1, which is effective as a heat source for the condenser, to be utilized. The flow rate of the refrigerant flowing through the heat medium relay unit D1 may also be appropriately adjusted using the high-pressure side solenoid valve 9d1. When the heat source-side heat exchanger 3 is not in use, the outdoor flow rate control device 3m may be stopped.

[0086] (Operation of the refrigeration cycle apparatus 100 in FIG. 3) FIG. 4 is a Mollier diagram of the refrigeration cycle apparatus 100 according to the first embodiment during cooling operation. As shown in FIG. 4, during cooling operation, the heat source-side heat exchanger 3 functions as a condenser, and the use-side heat exchanger 5 of the use-side unit C functions as an evaporator. Note that the number of use-side heat exchangers 5 shown in FIG. 4 may be multiple or may be single. The intermediate heat exchanger 30 is connected so that the refrigerant from the heat source-side heat exchanger 3 flows into it, and further cools the refrigerant. The refrigerant condensed in the heat source-side heat exchanger 3 and the intermediate heat exchanger 30 is decompressed by the flow control device 4, which is an expander, evaporated in the use-side heat exchangers 5 of the use-side units C1 and C2, and drawn into the compressor 1. The refrigeration cycle apparatus 100 performs a heat pump cycle by utilizing heat radiation in the heat source-side heat exchanger 3 and the intermediate heat exchanger 30 and heat absorption in the use-side heat exchangers 5c1 and 5c2. In particular, in the refrigeration cycle apparatus 100 shown in FIG. 3, by arranging the heat medium relay unit D1, which utilizes the external heat source E1 with a lower temperature, downstream of the heat source side heat exchanger 3, supercooling can be performed to the external heat source temperature t.

[0087] In addition, during cooling operation of the refrigeration cycle apparatus 100 shown in Figure 3, one of the two user-side units C1 and C2 can also be operated in heating operation. For example, when the user-side unit C2 in Figure 3 is operated in heating operation, the user-side heat exchanger 5c2 functions as a condenser. In this case, the second flow switching device 10c is controlled so that the low-pressure-side solenoid valve 8c2 is closed and the high-pressure-side solenoid valve 9c1 is opened, and the refrigerant from the high-pressure-side branch 10a flows into the user-side heat exchanger 5c2. In other words, as shown in Figure 4(b), the user-side heat exchanger 5c2 and the intermediate heat exchanger 30d1 are arranged in parallel in the refrigerant circuit.

[0088] (Regarding Operating Condition No. 2: Cooling Operation) Fig. 5 is an explanatory diagram of the flow of refrigerant when the refrigeration cycle apparatus 100 according to Embodiment 1 is operating in cooling mode. Fig. 5 shows the state of the refrigeration cycle apparatus 100 under operating condition No. 2 in Table 1 above. Operating condition No. 2 is a case where the outside air temperature T is lower than the external heat source temperature t. The refrigerant discharged from the compressor 1 is first condensed in the heat medium heat exchanger 30 and then in the heat source-side heat exchanger 3. This condenses the refrigerant to a temperature equivalent to the lower outside air temperature, ensuring an enthalpy difference between the refrigerant before and after passing through the condenser, thereby enabling further improvement in cooling capacity.

[0089] 5, as in FIG. 3, a cooling operation in which all of the user-side units C1 and C2 are cooling will be described. At this time, the control device 50 switches the first flow switching device 2a so that the refrigerant discharged from the compressor 1 flows to the heat-source-side heat exchanger 3. In addition, the low-pressure side solenoid valves 8c1 and 8c2 connected to the user-side units C1 and C2 are opened, and the high-pressure side solenoid valves 9c1 and 9c2 are closed. Note that some of the user-side units C1 and C2 can also be in heating operation. In this case, the low-pressure side solenoid valve 8 of the user-side unit C that is operating in heating operation is closed, and the high-pressure side solenoid valve 9 is opened.

[0090] When the compressor 1 starts operating, a low-temperature, low-pressure gaseous refrigerant is compressed by the compressor 1 and discharged as a high-temperature, high-pressure gaseous refrigerant. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1 flows into the third flow switching device 2b via the first flow switching device 2a. The third flow switching device 2b is switched to connect the external heat source circuit 90 to the first flow switching device 2a and the heat source side heat exchanger 3, so that the refrigerant that has flowed through the external heat source circuit 90 flows into the heat source side heat exchanger 3. The refrigerant that has been discharged from the compressor 1 and flowed into the external heat source circuit 90 flows from the pipe 91 into the heat medium related heat exchanger 30d1, where it exchanges heat with the heat medium flowing through the heat medium circulation circuit 34, is cooled while heating the heat medium, and becomes a medium-temperature, high-pressure liquid refrigerant or a gas-liquid two-phase refrigerant. The medium-temperature, high-pressure liquid refrigerant or gas-liquid two-phase refrigerant that has flowed out of the heat medium heat exchanger 30d1 returns to the third flow switching device 2b through the pipe 92, and flows into the heat source side heat exchanger 3 where it is further condensed. The medium-temperature, high-pressure refrigerant that has flowed out of the heat source side heat exchanger 3 passes through the high-pressure side pipe 7 and is separated into liquid refrigerant and gaseous refrigerant by the gas-liquid separation device 12. However, in the operating state shown in Fig. 5 , the refrigerant that has flowed into the gas-liquid separation device 12 is condensed in the heat medium heat exchanger 30d1 and the heat source side heat exchanger 3, and basically becomes high-pressure, medium-temperature subcooled liquid refrigerant.

[0091] The liquid refrigerant separated by the gas-liquid separator 12 flows into the second branch section 11, is decompressed and expanded by the first flow control devices 4c1 and 4c2 of the user-side units C1 and C2, is evaporated in the user-side heat exchanger 5, returns to the heat source unit A from the low-pressure-side branch section 10b, and is sucked into the low-pressure side of the compressor 1, as in the operating state shown in FIG.

[0092] 5, the low-pressure side solenoid valve 8d1 and the high-pressure side solenoid valve 9d1 of the second flow switching device 10c are closed, and the first branch section 10 is not connected to the relay unit D1. The second flow control device 4d1 of the relay unit D1 is also closed. As a result, the refrigerant that has passed through the relay unit B does not flow into the relay unit D1.

[0093] (Operation of the refrigeration cycle apparatus 100 in FIG. 5) FIG. 6 is a Mollier diagram of the refrigeration cycle apparatus 100 according to the first embodiment during cooling operation. As shown in FIG. 6, during cooling operation, the heat source-side heat exchanger 3 functions as a condenser, and the use-side heat exchanger 5 of the use-side unit C functions as an evaporator. Note that the number of use-side heat exchangers 5 shown in FIG. 6 may be multiple or single. The intermediate heat exchanger 30 is connected to receive the refrigerant from the compressor 1 and cools the refrigerant. Thereafter, as necessary, the refrigerant flows into the heat source-side heat exchanger 3 and is further cooled. The refrigerant condensed in the intermediate heat exchanger 30 and the heat source-side heat exchanger 3 is decompressed by the flow control device 4, which is an expander, evaporated in the use-side heat exchangers 5 of the use-side units C1 and C2, and drawn into the compressor 1. The refrigeration cycle apparatus 100 operates in a heat pump cycle by utilizing heat radiation in the heat source-side heat exchanger 3 and the intermediate heat exchanger 30 and heat absorption in the utilization-side heat exchangers 5c1 and 5c2. In particular, the refrigeration cycle apparatus 100 shown in Fig. 5 can supercool the refrigerant to the outdoor air temperature T by cooling and condensing the refrigerant using an external heat source E having a relatively higher temperature than the outdoor air, and further cooling the refrigerant using the outdoor air having a relatively lower temperature.

[0094] In addition, during cooling operation of the refrigeration cycle apparatus 100 shown in Figure 5, one of the two user-side units C1, C2 can also be operated in heating operation. For example, when the user-side unit C2 in Figure 5 is operated in heating operation, the user-side heat exchanger 5c2 functions as a condenser. In this case, the second flow switching device 10c is controlled so that the low-pressure-side solenoid valve 8c2 is closed and the high-pressure-side solenoid valve 9c1 is opened, and the refrigerant from the high-pressure-side branch 10a flows into the user-side heat exchanger 5c2. In other words, as shown in Figure 6(b), the user-side heat exchanger 5c2 is arranged in series downstream of the heat medium-to-heat medium heat exchanger 30d1 and the heat-source-side heat exchanger 3 in the refrigerant circuit.

[0095] (Operating Condition No. 3: Heating Operation) FIG. 7 is an explanatory diagram of the refrigerant flow when the refrigeration cycle apparatus 100 according to Embodiment 1 is performing heating operation. FIG. 7 shows the state of the refrigeration cycle apparatus 100 under operating condition No. 3 in Table 1. Operating condition No. 3 corresponds to a case where the external heat source temperature t is lower than the freezing threshold temperature f of the intermediate heat exchanger 30d1. The freezing threshold temperature f of the intermediate heat exchanger 30d1 varies depending on the performance of the intermediate heat exchanger 30d1 and is determined through testing. After being used for heating operation in the user side units C1 and C2, the refrigerant discharged from the compressor 1 flows into the intermediate heat exchanger 30d1 of the relay unit D1, which functions as an evaporator, where it evaporates. After evaporating, the refrigerant returns to the heat source unit A and is further evaporated in the heat source-side heat exchanger 3. The refrigeration cycle apparatus 100 can utilize the external heat source E to prevent freezing in the intermediate heat exchanger 30d1 by flowing the refrigerant through the intermediate heat exchanger 30d1 before the heat source-side heat exchanger 3. In an actual refrigeration cycle, low-pressure pressure loss occurs, causing the temperature at the outlet side of the evaporator to drop relative to the inlet side due to pipe resistance, and as shown in diagrams such as FIG. 8 , the line between points da and a slopes downward toward point a. Due to the low-pressure pressure loss, frost may form in the evaporator because a low-temperature refrigerant flows through it. However, under the operating conditions shown in FIG. 7 , even if the temperature t of the external heat source E1 is low, frost formation is suppressed because a relatively high-temperature refrigerant flows first into the intermediate heat exchanger 30d1. Furthermore, the refrigeration cycle apparatus 100 improves evaporation capacity by having the intermediate heat exchanger 30 function as an evaporator in addition to the heat source-side heat exchanger 3.

[0096] 7 illustrates a heating operation in which both the user side units C1 and C2 are performing heating. When the heating operation is performed, the control device 50 directly connects the first flow path switching device 2a to the high-pressure side pipe 7, and switches the refrigerant discharged from the compressor 1 to flow out of the high-pressure side pipe 7. In addition, the high-pressure side solenoid valves 9c1 and 9c2 connected to the user side units C1 and C2 are opened, and the low-pressure side solenoid valves 8c1 and 8c2 are closed.

[0097] When compressor 1 is operated, low-temperature, low-pressure gaseous refrigerant is compressed by compressor 1 and discharged as high-temperature, high-pressure gaseous refrigerant. The high-temperature, high-pressure gaseous refrigerant discharged from compressor 1 flows into high-pressure side branch section 10a of first branch section 10 via first flow switching device 2a and high-pressure side piping 7. The high-temperature, high-pressure gaseous refrigerant that has flowed into high-pressure side branch section 10a is branched, passes through high-pressure side solenoid valves 9c1 and 9c2, and flows into user-side heat exchangers 5c1 and 5c2. The refrigerant is then cooled while heating the indoor air, becoming a medium-temperature, high-pressure liquid refrigerant.

[0098] The medium-temperature, high-pressure liquid refrigerant flowing out of the user-side heat exchangers 5c1, 5c2 flows into the first flow control devices 4c1, 4c2. The refrigerant expands and is decompressed in the first flow control devices 4c1, 4c2 to become medium-temperature, medium-pressure, two-phase gas-liquid refrigerant, which then joins at the second branch section 11. The refrigerant that flows into the second branch section 11 flows into the second bypass pipe 14b or the heat medium relay unit D1.

[0099] A portion of the refrigerant that has flowed into the second branch section 11 passes through the second bypass pipe 14b and the fourth flow control device 15 and flows into the low-pressure branch section 10b of the first branch section 10. A portion of the refrigerant that has flowed into the second branch section 11 also flows into the relay unit D1. The refrigerant that has flowed into the relay unit D1 is expanded and decompressed to a medium-temperature and medium-pressure state in the second flow control device 4d1, and then evaporates through heat exchange with a heat medium from the external heat source E1 in the intermediate heat exchanger 30d1. The refrigerant then becomes a low-temperature, low-pressure gas refrigerant and flows into the low-pressure branch section 10b of the first branch section 10.

[0100] The refrigerant that joins at the low-pressure branch 10b passes through the low-pressure piping 6 and flows into the first flow control device 22, where it becomes a low-temperature, low-pressure, two-phase gas-liquid refrigerant, and is heated while cooling the outdoor air in the heat source heat exchanger 3, becoming a low-temperature, low-pressure gaseous refrigerant. Note that if the refrigerant that has entered the low-pressure piping 6 has become a sufficiently low-temperature, low-pressure gaseous refrigerant, it may be sent to the suction side of the compressor 1 via the bypass piping 25 without passing through the heat source heat exchanger 3.

[0101] Alternatively, all of the refrigerant flowing into the second branch section 11 from the user-side units C1 and C2 operating in heating mode may be directed to the heat medium relay unit D1. This allows the entire amount of refrigerant to be evaporated using the external heat source E1, reducing the load on the heat-source-side heat exchanger 3 and leading to energy savings. If the entire amount of refrigerant can be converted into a sufficiently low-temperature, low-pressure gas refrigerant in the heat medium relay unit D1, the refrigeration cycle apparatus 100 may draw the refrigerant into the compressor 1 without using the outdoor flow rate control device 3m or the heat-source-side heat exchanger 3.

[0102] As described above, in the heating operation of the refrigeration cycle apparatus 100, not only the heat source side heat exchanger 3 is used as an evaporator, but also the heat medium relay unit D1 can be used as an evaporator. Therefore, in the heat source unit A, the output of the outdoor flow control device 3m that sends air to the heat source side heat exchanger 3 may be reduced, or part of the refrigerant flowing through the heat source side heat exchanger 3 may be bypassed and drawn into the compressor 1. The refrigerant that does not pass through the heat source side heat exchanger 3 but passes through the bypass piping 25 flows into the accumulator 29 and is drawn into the compressor 1. In this way, the heat medium relay unit D1 can complement the capacity of the heat source side heat exchanger 3 by utilizing the external heat source E1.

[0103] Depending on the capacity of the heat medium relay unit D1, the heat source unit A can be configured so that the refrigerant does not flow into the heat source-side heat exchanger 3 and is entirely drawn into the compressor 1 through the bypass piping 25. In the heat medium relay unit D1, the refrigerant becomes a low-temperature, low-pressure gas refrigerant and passes through the low-pressure side branch section 10b, the low-pressure side piping 6, the second flow control device 26, the bypass piping 25, and the first flow switching device 2a before being drawn into the compressor 1. In Fig. 6, the bypass piping 25 is preferably connected between the first flow switching device 2a and the third flow switching device 2b.

[0104] (Operation of the refrigeration cycle apparatus 100 in FIG. 7) FIG. 8 is a Mollier diagram of the refrigeration cycle apparatus 100 according to the first embodiment during heating operation. As shown in FIG. 8, during heating operation, the use-side heat exchanger 5 functions as a condenser, and the intermediate heat exchanger 30 and the heat-source-side heat exchanger 3 function as evaporators. The use-side heat exchanger 5 shown in FIG. 8 may be provided in a single or multiple locations. The intermediate heat exchanger 30 is connected before the heat-source-side heat exchanger 3 so that the refrigerant flows in, and heats the refrigerant. The refrigerant condensed in the use-side heat exchanger 5 is decompressed by the flow control device 4, which is an expander, and evaporates in the heat medium relay unit D and the heat source unit A. The refrigeration cycle apparatus 100 performs a heat pump cycle by utilizing the heat absorption in the heat-source-side heat exchanger 3 and the intermediate heat exchanger 30 and the heat release in the use-side heat exchangers 5c1 and 5c2. In particular, in the refrigeration cycle apparatus 100 shown in FIG. 8 , the heat medium relay unit D1, which utilizes an external heat source E whose temperature is lower than the freezing threshold, is located upstream of the heat source-side heat exchanger 3. This arrangement can suppress frost formation on the heat medium relay unit D1 while assisting or complementing the ability of the heat source-side heat exchanger 3 to function as an evaporator.

[0105] In addition, during heating operation of the refrigeration cycle apparatus 100 shown in Figure 7, one of the two user-side units C1, C2 can also be operated in cooling operation. For example, when the user-side unit C2 in Figure 7 is operated in cooling operation, the user-side heat exchanger 5c2 functions as an evaporator. In this case, the second flow switching device 10c is controlled so that the low-pressure side solenoid valve 8c2 is opened and the high-pressure side solenoid valve 9c2 is closed, and the refrigerant from the second branch section 11 flows into the user-side heat exchanger 5c2 via the flow control device 4c2. In other words, as shown in Figure 8(b), the user-side heat exchanger 5c2 and the intermediate heat exchanger 30 are arranged in parallel in the refrigerant circuit.

[0106] (Operating Condition No. 4: Heating Operation) Fig. 9 is an explanatory diagram of the refrigerant flow when the refrigeration cycle apparatus 100 according to Embodiment 1 is performing heating operation. Fig. 9 shows the state of the refrigeration cycle apparatus 100 under operating condition No. 4 in Table 1. Operating condition No. 4 corresponds to a case where the external heat source temperature t is higher than the freezing threshold temperature f of the intermediate heat exchanger 30d1. After being used for heating operation in the user side units C1 and C2, the refrigerant discharged from the compressor 1 flows into the heat source side heat exchanger 3, which functions as an evaporator, and is evaporated. Thereafter, the refrigerant flows through the third flow switching device 2b into the intermediate heat exchanger 30d1 of the relay unit D1 and is further evaporated. As a result, a refrigerant with a relatively high temperature is flowed into the heat source side heat exchanger 3, so that frost formation in the heat source side heat exchanger 3 is suppressed. In addition, the refrigerant whose temperature has been lowered due to the low pressure drop is flowed into the heat medium-to-heat medium heat exchanger 30, which is free from the risk of freezing, and evaporated, thereby improving the evaporation capacity of the refrigeration cycle apparatus 100 as a whole.

[0107] 9 will be used to explain the case where both of the utilization side units C1 and C2 are in heating operation, as in the case of FIG. 7. When the heating operation is performed, the control device 50 directly connects the first flow path switching device 2a to the high-pressure side pipe 7, and switches the refrigerant discharged from the compressor 1 to flow out of the high-pressure side pipe 7. In addition, the high-pressure side solenoid valves 9c1 and 9c2 connected to the utilization side units C1 and C2 are opened, and the low-pressure side solenoid valves 8c1 and 8c2 are closed.

[0108] When the compressor 1 is operated, a low-temperature, low-pressure gaseous refrigerant is compressed by the compressor 1 and discharged as a high-temperature, high-pressure gaseous refrigerant. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1 flows into the user-side units C1 and C2 from the high-pressure side branch 10a of the first branch 10, as in the case of Fig. 7. The high-temperature, high-pressure gaseous refrigerant that has flowed into the user-side units C1 and C2 is heated while cooling the indoor air, and becomes a medium-temperature, high-pressure liquid or two-phase gas-liquid refrigerant that flows into the second branch 11. The liquid or two-phase gas-liquid refrigerant that has flowed into the second branch 11 flows into the low-pressure side branch via the second bypass piping 14b and returns to the heat source unit A.

[0109] The refrigerant returned to the heat source unit A is evaporated in the heat source-side heat exchanger 3, and then flows into the external heat source circuit 90 through the third flow switching device 2b and is sent to the heat medium relay unit D. In the heat medium relay unit D, the refrigerant is further evaporated in the intermediate heat exchanger 30d1, returns to the heat source unit A again, and is sucked into the compressor 1 through the first flow switching device 2a. Note that part or all of the refrigerant flowing through the heat source-side heat exchanger 3 can be circulated using the bypass piping 25. In FIG. 9 , the bypass piping 25 is preferably connected between the heat source-side heat exchanger 3 and the third flow switching device 2b.

[0110] In the operating state shown in FIG. 9, the low-pressure side solenoid valve 8d1 and the high-pressure side solenoid valve 9d1 of the second flow path switching device 10c are closed, and the first branch section 10 and the heat medium relay unit D1 are not connected to each other.

[0111] (Operation of the refrigeration cycle apparatus 100 in FIG. 9 ) FIG. 10 is a Mollier diagram of the refrigeration cycle apparatus 100 according to the first embodiment during heating operation. As shown in FIG. 10 , during heating operation, the use-side heat exchanger 5 functions as a condenser, and the intermediate heat exchanger 30 and the heat-source-side heat exchanger 3 function as evaporators. The use-side heat exchanger 5 shown in FIG. 10 may be provided in a single or multiple locations. The intermediate heat exchanger 30 is connected after the heat-source-side heat exchanger 3 so that the refrigerant flows in, and heats the refrigerant. The refrigerant condensed in the use-side heat exchanger 5 is decompressed by the flow control device 4, which is an expander, and evaporates in the heat medium relay unit D and the heat source unit A. The refrigeration cycle apparatus 100 performs a heat pump cycle by utilizing the heat absorption in the heat-source-side heat exchanger 3 and the intermediate heat exchanger 30 and the heat release in the use-side heat exchangers 5c1 and 5c2. 9 , an external heat source E having a temperature higher than the freezing threshold is used, and a heat medium relay unit D1, which is free from the risk of freezing, is located downstream of the heat source-side heat exchanger 3, thereby improving evaporation capacity while avoiding the risk of freezing due to low-pressure pressure loss. Furthermore, by first flowing a relatively high-temperature refrigerant into the heat source-side heat exchanger 3, frost formation in the heat source-side heat exchanger 3 is suppressed.

[0112] In addition, during heating operation of the refrigeration cycle apparatus 100 shown in Figure 9, one of the two user-side units C1, C2 can also be operated in cooling operation. For example, when the user-side unit C2 in Figure 9 is operated in cooling operation, the user-side heat exchanger 5c2 functions as an evaporator. In this case, the second flow switching device 10c is controlled so that the low-pressure-side solenoid valve 8c2 is opened and the high-pressure-side solenoid valve 9c2 is closed, and the refrigerant from the second branch section 11 flows into the user-side heat exchanger 5c2 via the flow control device 4c2. In other words, as shown in Figure 10(b), the user-side heat exchanger 5c2 is arranged in series with the heat-source-side heat exchanger 3 and the intermediate heat exchanger 30 in the refrigerant circuit.

[0113] (Operating Condition No. 5: Heating Operation) The operating condition No. 5 in Table 1 corresponds to a case where the external heat source temperature t is lower than the freezing threshold temperature f of the intermediate heat exchanger 30d1. The refrigeration cycle apparatus 100 under the operating condition No. 5 in Table 1 can also perform conventional heating operation without using the intermediate heat exchanger 30. In this case, the second flow switching device 10c closes the low-pressure side solenoid valve 8d1 and the high-pressure side solenoid valve 9d1, and the third flow switching device 2b is switched to connect the heat source side heat exchanger 3 and the first flow switching device 2a, preventing refrigerant from flowing through the relay unit D1. In this way, when the external heat source temperature t is lower than the freezing threshold temperature f of the intermediate heat exchanger 30d1, the refrigeration cycle apparatus 100 can protect the intermediate heat exchanger 30d1 without using it.

[0114] (Operating Condition No. 6: Defrosting Operation) FIG. 11 is an explanatory diagram of the refrigerant flow when the refrigeration cycle apparatus 100 according to Embodiment 1 is performing defrosting operation. FIG. 11 shows the state of the refrigeration cycle apparatus 100 under operating condition No. 6 in Table 1. Operating condition No. 6 involves continuing heating operations of the user-side units C1 and C2 while flowing hot gas into the heat-source-side heat exchanger 3 to perform defrosting. Note that operating condition No. 6 is a condition in which the external heat source temperature t is higher than the freezing threshold temperature f of the intermediate heat exchanger 30d1. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1 flows from the first flow switching device 2a through the third flow switching device 2b and directly into the heat-source-side heat exchanger 3 to perform defrosting. The refrigerant exiting the heat-source-side heat exchanger 3 is sent to the user-side units C1 and C2, where it is cooled and condensed while heating indoor air, etc. The refrigerant flowing out of the user units C2 and C2 joins at the second branch 11 and flows into the heat medium relay unit D1. In the heat medium relay unit D1, the refrigerant is evaporated using heat from the external heat source E1. The evaporated refrigerant returns to the heat source unit A via the low-pressure side pipe 6, passes through the first flow switching device 2a, and passes through the accumulator 29, and is drawn into the compressor 1.

[0115] (Operation of the refrigeration cycle apparatus 100 in FIG. 11 ) FIG. 12 is a Mollier diagram during defrost operation of the refrigeration cycle apparatus 100 according to the first embodiment. During the defrost operation shown in FIG. 12 , the heat source-side heat exchanger 3 performing defrosting and the use-side heat exchanger 5 performing heating operation function as condensers, and the intermediate heat exchanger 30 functions as an evaporator. Note that the use-side heat exchanger 5 shown in FIG. 12 may be provided in multiple or single units. The intermediate heat exchanger 30 is connected after the heat source-side heat exchanger 3 and the use-side units C1 and C2 so that the refrigerant flows in, and heats the refrigerant. As a result, the refrigeration cycle apparatus 100 can perform a defrosting operation of the heat source-side heat exchanger 3 while continuing heating operation by using the external heat source E1.

[0116] (Operating Condition No. 7: Defrosting Operation) FIG. 13 is an explanatory diagram of the refrigerant flow when the refrigeration cycle apparatus 100 according to Embodiment 1 is performing defrosting operation. FIG. 13 shows the state of the refrigeration cycle apparatus 100 under operating condition No. 7 in Table 1. Operating condition No. 7 is a case in which the external heat source temperature t is lower than the freezing threshold temperature f of the heat medium heat exchanger 30d1. The heating operations of the user-side units C1 and C2 are stopped, and hot gas is passed through the heat-source-side heat exchanger 3 to perform defrosting. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1 flows from the first flow switching device 2a to the third flow switching device 2b and directly into the heat-source-side heat exchanger 3 to perform defrosting. The refrigerant exiting the heat-source-side heat exchanger 3 flows through the gas-liquid separator 12, the second branch 11, and the heat medium relay unit D1, where it is evaporated. The refrigerant that has flowed out of the heat medium relay unit D1 returns to the heat source unit A via the low-pressure side pipe 6, and is then drawn into the compressor 1 via the first flow switching device 2a and the accumulator 29.

[0117] (Operation of the refrigeration cycle apparatus 100 in FIG. 13) FIG. 14 shows a Mollier diagram during defrost operation of the refrigeration cycle apparatus 100 according to Embodiment 1. During the defrost operation shown in FIG. 14 , only the heat source side heat exchanger 3 that performs defrosting functions as a condenser, and the intermediate heat exchanger 30 functions as an evaporator. The intermediate heat exchanger 30 is connected after the heat source side heat exchanger 3 so that the refrigerant flows in, and heats the refrigerant. The refrigeration cycle apparatus 100 can perform the defrost operation of the heat source side heat exchanger 3 in a short time by using the external heat source E1 as an evaporator.

[0118] No. 8 in Table 1 corresponds to a case where the external heat source temperature t is lower than the freezing threshold temperature f of the intermediate heat exchanger 30d1, and in this case, no refrigerant flows through the intermediate heat exchanger 30d1, and the defrosting operation is performed only by the compressor 1.

[0119] As described above, the refrigeration cycle apparatus 100 according to the first embodiment is configured so that the heat medium relay unit D1 utilizing the external heat source E can be used to supplement or complement the heat source-side heat exchanger 3, and further so that the heat medium relay unit D1 can be appropriately connected upstream or downstream of the heat source-side heat exchanger 3. This allows the refrigeration cycle apparatus 100 to appropriately use the heat medium relay unit D1 depending on the temperature of the external heat source E1, and to more efficiently use the heat medium relay unit D1 as an auxiliary heat source.

[0120] Embodiment 2 A refrigeration cycle apparatus 200 according to Embodiment 2 is a refrigeration cycle apparatus 100 according to Embodiment 1 provided with a plurality of heat medium relay units D1, D2. The following description will focus on the differences between Embodiment 2 and Embodiment 1.

[0121] 15 is an example of a circuit diagram showing a refrigeration cycle apparatus 200 according to Embodiment 2. The refrigeration cycle apparatus 200 includes a heat medium relay unit D2 in addition to the components of Embodiment 1. The heat medium relay unit D2 is connected to the relay unit B in the same manner as the heat medium relay unit D1, and is also directly connected to the heat source unit A.

[0122] The heat source unit A and the heat medium relay units D1 and D2 are connected via an external heat source circuit 90. Pipes 91 and 92 extending from the third flow switching device 2b of the heat source unit A branch off from the external heat source circuit 90, and are connected to the heat medium relay units D1 and D2, respectively. The pipe 91 is connected to the second connection pipes 41d1 and 41d2, and the pipe 92 is connected to the first connection pipes 40d1 and 40d2, respectively. The pipe 91 is provided with on-off valves 94d1 and 94d2, respectively, on the branched pipes, and it is possible to select whether or not to circulate the refrigerant from the heat source unit A through the intermediate heat exchangers 30d1 and 30d2.

[0123] In the refrigeration cycle apparatus 200 according to the second embodiment, the two heat medium relay units D1 and D2 can be used in the same way, or one can receive a refrigerant directly from the heat source unit A, and the other can receive a refrigerant via the relay unit B. When using two external heat sources E1 and E2 with different temperatures, the refrigeration cycle apparatus 200 can selectively use the heat medium relay units D1 and D2 depending on the relationship between the external heat source temperature t and the outside air temperature T or the freezing threshold temperature f. This allows the heat medium relay units D1 and D2 to efficiently assist or complement the performance of the heat source-side heat exchanger 3 as a condenser or evaporator depending on the environment. Although two heat medium relay units D are connected to the refrigeration cycle apparatus 200 in the second embodiment, more units may be installed.

[0124] 15 , a plurality of heat medium relay units D can be installed in parallel with the relay unit B, allowing a plurality of external heat sources E to be used for the refrigeration cycle apparatus 200. For example, when the refrigeration cycle apparatus 200 is in cooling or cooling-dominated operation, the heat source-side heat exchanger 3 functions as a condenser, and the heat medium relay unit D1 using well water as the external heat source E1 also functions as a condenser, thereby allowing the heat medium relay unit D1 to supplement the capacity of the heat source-side heat exchanger 3 during cooling or cooling-dominated operation. Furthermore, when the refrigeration cycle apparatus 100 is in heating or heating-dominated operation, the heat source-side heat exchanger 3 functions as an evaporator, and the heat medium relay unit D2 using sunlight as the external heat source E2 also functions as an evaporator, allowing the heat medium relay unit D2 to supplement the capacity of the heat source-side heat exchanger 3 during heating or heating-dominated operation.

[0125] The refrigeration cycle apparatus 200 according to the second embodiment enables simultaneous cooling and heating operation by appropriately selecting the operating state of the plurality of user-side units C from cooling, heating, and hot water heating operation by switching the connection between the heat source unit A and the user-side units C using the second flow switching device 10c. In addition, the refrigeration cycle apparatus 200 can appropriately switch the external heat source E to be used as an auxiliary for or a substitute for the heat source-side heat exchanger 3 by switching the connection state with the plurality of heat medium relay units D using the second flow switching device 10c.

[0126] As described above, the first and second embodiments of the present disclosure have been described. However, the first and second embodiments are merely examples of the refrigeration cycle apparatuses 100 and 200, and may be combined with other known technologies. Furthermore, the configurations of the refrigeration cycle apparatuses 100 and 200 may be partially omitted or modified without departing from the spirit and scope of the present disclosure. In short, the refrigeration cycle apparatuses 100 and 200 include design modifications and application variations that are normally made by a person skilled in the art, without departing from the technical concept thereof.

[0127] 1 Compressor, 2 Heat source side flow switching device, 2a First flow switching device, 2b Third flow switching device, 3 Heat source side heat exchanger, 3m Outdoor flow control device, 3t Temperature sensor, 4 Flow control device, 4c1 (First) flow control device, 4c2 (First) flow control device, 4d1 (Second) flow control device, 5 Use side heat exchanger, 5c1 Use side heat exchanger, 5c2 Use side heat exchanger, 5m Flow control device, 6 Low pressure side piping, 7 High pressure side piping, 8 Low pressure side solenoid valve, 8c1 Low pressure side solenoid valve, 8c2 Low pressure side solenoid valve, 8d1 Low pressure side solenoid valve, 9 High pressure side solenoid valve, 9c1 High pressure side solenoid valve, 9c2 High pressure side solenoid valve, 9d1 High pressure side solenoid valve, 10 First branch, 10a High pressure side branch, 10b Low pressure side branch, 10c DESCRIPTION OF SYMBOLS Second flow switching device, 11 Second branching portion, 12 Gas-liquid separator, 13 Third flow control device, 14 Fourth flow control device, 14a First bypass pipe, 14b Second bypass pipe, 15 Fourth flow control device, 16 Second heat exchanger, 17 First heat exchanger, 18 Check valve, 19 Check valve, 20 Check valve, 21 Check valve, 22 First flow control device, 25 Bypass pipe, 26 Second flow control device, 27 First pipe, 29 Accumulator, 30 Inter-heat medium heat exchanger, 30d1 Inter-heat medium heat exchanger, 30d2 Inter-heat medium heat exchanger, 31 Pump, 32 External heat source temperature sensor, 33 External heat source temperature sensor, 34 Heat medium circulation circuit, 40 First connecting pipe, 40c1 First connecting pipe, 40c2 First connecting pipe, 40d1 First connecting pipe, 40d2 First connecting pipe, 41 Second connecting pipe, 41c1 Second connecting pipe, 41c2 Second connecting pipe, 41d1 Second connecting pipe, 41d2 Second connecting pipe, 50 Control device, 50a Memory, 51 Discharge pressure gauge, 52 Suction pressure gauge, 53 Medium pressure gauge, 54 Thermometer, 60a First connecting pipe, 60b Second connecting pipe, 90 External heat source circuit, 91 Pipe, 92 Pipe, 93 On-off valve, 94d1 On-off valve, 94d2 On-off valve, 100 Refrigeration cycle device, 200 Refrigeration cycle device, A Heat source device, B Relay device, C Use side unit, C1 Use side unit, C2 Use side unit, C3 Use side unit, D Heat medium converter, D1 Heat medium converter, D12 Heat medium converter, D2 Heat medium converter, E External heat source, E1 External heat source, E2 External heat source, F external heat exchanger.

Claims

1. A heat source machine having a compressor for compressing a refrigerant, a heat source side heat exchanger, and a first flow path switching device for switching the flow path of the refrigerant, A high-pressure side pipe through which the refrigerant flows out from the heat source machine, A low-pressure side pipe through which the refrigerant flows in and out of the heat source machine, A utilization side unit connected to the high-pressure side pipe and the low-pressure side pipe, having a utilization side heat exchanger and a first flow rate control device for controlling the flow rate of the refrigerant flowing through the utilization side heat exchanger, A heat medium converter having a heat medium-to-refrigerant heat exchanger for exchanging heat between a heat medium that transports heat from an external heat source and the refrigerant, and a second flow rate control device for controlling the flow rate of the refrigerant flowing through the heat medium-to-refrigerant heat exchanger, A first branch portion that branches each of the high-pressure side pipe and the low-pressure side pipe to the utilization side unit and is connected to a first connection pipe extending from the utilization side unit, A second branch portion connected to a second connection pipe extending from the first flow rate control device, An external heat source circuit for circulating the refrigerant between the heat source machine and the heat medium converter without passing through the first branch portion and the second branch portion, The first branch portion, Comprises a second flow path switching device for switching the connection between the first connection pipe and the high-pressure side pipe or the low-pressure side pipe, The first flow path switching device, When the heat source side heat exchanger functions as a condenser, it is connected so that the refrigerant flows from the discharge side of the compressor through the heat source side heat exchanger to the high-pressure side pipe, and the refrigerant flows from the low-pressure side pipe to the suction side of the compressor, When the heat source side heat exchanger functions as an evaporator, it is configured to be connected so that the refrigerant flows from the discharge side of the compressor to the high-pressure side pipe, and the refrigerant flows from the low-pressure side pipe through the heat source side heat exchanger to the suction side of the compressor, The external heat source circuit, Is configured to allow the refrigerant to flow between the discharge side or the suction side of the compressor and the heat source side heat exchanger via the heat medium-to-refrigerant heat exchanger, A refrigeration cycle device.

2. The heat medium converter, Further comprises a first connection pipe connected to the first branch portion, And a second connection pipe extending from the second flow rate control device and connected to the second branch portion, The second flow path switching device, The heat medium interchanger is configured to be able to function as an auxiliary evaporator when the heat source side heat exchanger functions as an evaporator, so that the heat medium interchanger can function as an auxiliary condenser when the heat source side heat exchanger functions as a condenser. The refrigeration cycle device according to claim 1.

3. The heat source machine further includes a third flow path switching device connected between the first flow path switching device and the heat source side heat exchanger, The third flow path switching device is connected to the external heat source circuit and can switch the refrigerant flowing between the compressor and the heat source side heat exchanger to flow to the heat medium interchanger. The refrigeration cycle device according to claim 1 or 2.

4. includes a control device for controlling the first flow path switching device, the second flow path switching device, and the third flow path switching device, The control device when the relationship between the outside air temperature T and the external heat source temperature t is t > T during cooling operation, or when the relationship between the freezing threshold temperature f of the heat medium interchanger and the external heat source temperature t is t > f during heating operation, controls the third flow path switching device to cause the refrigerant to flow through the external heat source circuit, and controls the second flow path switching device to stop the flow of the refrigerant between the first branch portion and the heat medium converter. The refrigeration cycle device according to claim 3.

5. includes a control device for controlling the first flow path switching device, the second flow path switching device, and the third flow path switching device, The control device when the relationship between the outside air temperature T and the external heat source temperature t is t < T during cooling operation, or when the relationship between the freezing threshold temperature f of the heat medium interchanger and the external heat source temperature t is t < f during heating operation, controls the third flow path switching device to prevent the refrigerant from flowing through the external heat source circuit, and controls the second flow path switching device to cause the refrigerant to flow between the first branch portion and the heat medium converter. The refrigeration cycle device according to claim 3.

6. includes a control device for controlling the first flow path switching device, the second flow path switching device, and the third flow path switching device, The control device controls the third flow path switching device to prevent the refrigerant from flowing through the external heat source circuit, and controls the second flow path switching device to stop the flow of the refrigerant between the first branch portion and the heat medium converter. The refrigeration cycle device according to claim 3.