Patent Application
20230056663
The present disclosure relates to a refrigeration cycle system.
Conventionally, there is known a dual refrigeration apparatus in which a primary-side refrigerant circuit and a secondary-side refrigerant circuit are connected via a cascade heat exchanger. In the case of using a carbon dioxide refrigerant in the secondary-side refrigerant circuit of such a dual refrigeration apparatus, the pressure of the discharged refrigerant transiently increases at the start of the secondary-side refrigerant circuit, and thus there is a problem that the design pressure in the secondary-side refrigerant circuit increases.
Regarding this matter, for example, a refrigeration apparatus described in Patent Literature 1 (JP 2004-190917 A) proposes that a compressor constituting a primary-side refrigerant circuit is started before a compressor constituting a secondary-side refrigerant circuit is started in order to suppress the transient increase in the discharge refrigerant pressure at the start of the secondary-side refrigerant circuit.
A refrigeration cycle system according to a first aspect includes a first cycle and a second cycle. The first cycle includes a first compressor, a cascade heat exchanger, a first expansion unit, and a first heat exchanger, which are connected to each other. In the first cycle, a carbon dioxide refrigerant circulates. The first cycle includes a first flow path, a second flow path, a third flow path, and a bypass flow path. The first flow path connects the first compressor to the cascade heat exchanger. The second flow path connects the cascade heat exchanger to the first expansion unit. The third flow path connects the first heat exchanger to the first compressor. The bypass flow path connects at least one of the first flow path and the second flow path to the third flow path. The second cycle includes the cascade heat exchanger. In the second cycle, a heat medium different from the carbon dioxide refrigerant circulates. In the refrigeration cycle system, in the case of using the cascade heat exchanger as a radiator of the first cycle and a heat sink of the second cycle, the first compressor of the first cycle is started after a flow of the heat medium generates in the cascade heat exchanger in the second cycle.
The refrigeration cycle system 1 is an apparatus used for cooling and heating of a room of such as a building by performing a vapor compression refrigeration cycle operation.
The refrigeration cycle system 1 includes a primary-side unit 5 and a secondary-side unit 4 (corresponding to a refrigeration cycle apparatus), and includes a dual refrigerant circuit that performs a dual refrigeration cycle.
The primary-side unit 5 includes a vapor compression primary-side refrigerant circuit 5a (corresponding to a second cycle). In the primary-side refrigerant circuit 5a, R32 (corresponding to a heat medium) or the like is sealed as a refrigerant.
The secondary-side unit 4 includes a vapor compression secondary-side refrigerant circuit 10 (corresponding to a first cycle). In the secondary-side refrigerant circuit 10, carbon dioxide is sealed as a refrigerant. The primary-side unit 5 and the secondary-side unit 4 are connected via a cascade heat exchanger 35 to be described later.
The secondary-side unit 4 has a configuration in which a plurality of branch units 6a, 6b, and 6c corresponding to the utilization units 3a, 3b, and 3c, respectively, are respectively connected via first connecting pipes 15a, 15b, and 15c and second connecting pipes 16a, 16b, and 16c, and the plurality of branch units 6a, 6b, and 6c is connected to a heat source unit 2 via three connection pipes 7, 8, and 9. In the present embodiment, the number of the plurality of utilization units 3a, 3b, and 3c provided is three, which are the first utilization unit 3a, the second utilization unit 3b, and the third utilization unit 3c. In the present embodiment, the number of the plurality of branch units 6a, 6b, and 6c provided is three, which are the first branch unit 6a, the second branch unit 6b, and the third branch unit 6c. In the present embodiment, the number of the heat source unit 2 provided is one. The three connection pipes are respectively referred to as the first connection pipe 8, the second connection pipe 9, and the third connection pipe 7. Any one of the refrigerant in the supercritical state, the refrigerant in the gas-liquid two-phase state, and the refrigerant in the gas state flows through the first connection pipe 8 according to the operation state. Any one of the refrigerant in the gas-liquid two-phase state and the refrigerant in the gas state flows through the second connection pipe 9 according to the operation state. Any one of the refrigerant in the supercritical state, the refrigerant in the gas-liquid two-phase state, and the refrigerant in the liquid state flows through the third connection pipe 7 according to the operation state.
In addition, in the refrigeration cycle system 1, the utilization units 3a, 3b, and 3c can individually perform cooling operation or heating operation, and heat recovery can be performed between the utilization units by sending the refrigerant from the utilization unit performing the heating operation to the utilization unit performing the cooling operation. Specifically, in the present embodiment, the heat recovery is performed by performing the cooling dominant operation and the heating dominant operation in which the cooling operation and the heating operation are simultaneously performed. The refrigeration cycle system 1 is configured to balance the heat load of the heat source unit 2 in accordance with the heat load of the whole of the plurality of utilization units 3a, 3b, and 3c in consideration of the above-described heat recovery (the cooling dominant operation and the heating dominant operation).
The primary-side unit 5 includes a primary-side refrigerant circuit 5a, a primary-side fan 75, and a primary-side control unit 70.
The primary-side refrigerant circuit 5a includes a primary-side compressor 71 (corresponding to a second compressor), a primary-side switching mechanism 72, a primary-side heat exchanger 74, a primary-side expansion valve 76, and a cascade heat exchanger 35 shared with the secondary-side refrigerant circuit 10. The primary-side refrigerant circuit 5a constitutes a primary-side refrigerant circuit in the refrigeration cycle system 1, and has a refrigerant such as R32 circulated therein.
The primary-side compressor 71 is a device for compressing a primary-side refrigerant, and includes, for example, a scroll type or other positive displacement compressor whose operating capacity can be varied by inverter-controlling a compressor motor 71a.
In the case where the cascade heat exchanger 35 is made to function as an evaporator for the primary-side refrigerant, the primary-side switching mechanism 72 is brought into a fifth connection state where the suction side of the primary-side compressor 71 is connected to the gas side of a primary-side flow path 35b of the cascade heat exchanger 35 (see a solid line of the primary-side switching mechanism 72 in
The cascade heat exchanger 35 is a device for performing heat exchange between the refrigerant such as R32, which is the primary-side refrigerant, and carbon dioxide, which is the secondary-side refrigerant, without mixing the refrigerants with each other. The cascade heat exchanger 35 is, for example, a plate-type heat exchanger. The cascade heat exchanger 35 includes a secondary-side flow path 35a belonging to the secondary-side refrigerant circuit 10 and the primary-side flow path 35b belonging to the primary-side refrigerant circuit 5a. The secondary-side flow path 35a has the gas side connected to a secondary-side switching mechanism 22 via a third heat source pipe 25 (corresponding to a first flow path), and a liquid side connected to a secondary-side expansion valve 36 via a fourth heat source pipe 26 (corresponding to a second flow path). The primary-side flow path 35b has the gas side connected to the primary-side compressor 71 via the primary-side switching mechanism 72 and the liquid side connected to the primary-side expansion valve 76.
The primary-side expansion valve 76 is provided in a liquid pipe between the cascade heat exchanger 35 and the primary-side heat exchanger 74 of the primary-side refrigerant circuit 5a. The primary-side expansion valve 76 is an electrically powered expansion valve whose opening degree can be controlled and that performs control and the like of the flow rate of the primary-side refrigerant flowing through the liquid side portion of the primary-side refrigerant circuit 5a.
The primary-side heat exchanger 74 is a device for exchanging heat between the primary-side refrigerant and the indoor air, and includes, for example, a fin-and-tube heat exchanger including a large number of heat transfer tubes and fins.
The primary-side fan 75 is provided in the primary-side unit 5, and generates an air flow that guides the outdoor air to the primary-side heat exchanger 74, exchanges heat with the primary-side refrigerant flowing through the primary-side heat exchanger 74, and then discharges the air to the outdoors. The primary-side fan 75 is driven by a primary-side fan motor 75a.
Further, the primary-side unit 5 is provided with various sensors. Specifically, the primary-side unit 5 is provided with an outside air temperature sensor 77 that detects the temperature of the outdoor air before the air passes through the primary-side heat exchanger 74, and a primary-side discharge pressure sensor 78 that detects the pressure of the primary-side refrigerant discharged from the primary-side compressor 71.
The primary-side control unit 70 controls operation of respective units 71 (71a), 72, 75 (75a), and 76 that constitute the primary-side unit 5. Further, the primary-side control unit 70 includes a processor such as a CPU and a microcomputer, and a memory, which are provided for controlling the primary-side unit 5, and is configured to be able to exchange control signals and the like with a remote controller (not shown), and exchange control signals and the like with a heat source-side control unit 20, branch unit control units 60a, 60b, and 60c, and utilization-side control units 50a, 50b, and 50c of the secondary-side unit 4.
The secondary-side unit 4 is configured by connecting the plurality of utilization units 3a, 3b, and 3c, the plurality of branch units 6a, 6b, and 6c, and the heat source unit 2 to each other. The utilization units 3a, 3b, and 3c are connected one-to-one with the corresponding branch units 6a, 6b, and 6c. Specifically, the utilization unit 3a and the branch unit 6a are connected via the first connecting pipe 15a and the second connecting pipe 16a, the utilization unit 3b and the branch unit 6b are connected via the first connecting pipe 15b and the second connecting pipe 16b, and the utilization unit 3c and the branch unit 6c are connected via the first connecting pipe 15c and the second connecting pipe 16c. Further, each of the branch units 6a, 6b, and 6c is connected to the heat source unit 2 via three connection pipes, that is, the third connection pipe 7, the first connection pipe 8, and the second connection pipe 9. Specifically, each of the third connection pipe 7, the first connection pipe 8, and the second connection pipe 9 extending from the heat source unit 2 is branched into a plurality of pipes and connected to the respective branch units 6a, 6b, and 6c.
(3-1) Utilization Unit
The utilization units 3a, 3b, and 3c are installed, such as by being embedded in or suspended from a ceiling in a room such as a building, or by being hung on a wall surface in the room. The utilization units 3a, 3b, and 3c are connected to the heat source unit 2 via the connection pipes 7, 8, and 9, and respectively include utilization circuits 13a, 13b, and 13c constituting a part of the secondary-side refrigerant circuit 10.
Next, configurations of the utilization units 3a, 3b, and 3c are described. Note that, because the second utilization unit 3b and the third utilization unit 3c have the similar configuration with the first utilization unit 3a, only the configuration of the first utilization unit 3a is described herein. For the configurations of the second utilization unit 3b and the third utilization unit 3c, instead of a suffix “a” indicating each part of the first utilization unit 3a, a suffix “b” or “c” is added, respectively, and the description of each part is omitted.
The first utilization unit 3a mainly includes a utilization circuit 13a, an indoor fan 53a, and a utilization-side control unit 50a, which constitute a part of the secondary-side refrigerant circuit 10. The indoor fan 53a includes an indoor fan motor 54a. The second utilization unit 3b includes a utilization circuit 13b, an indoor fan 53b, a utilization-side control unit 50b, and an indoor fan motor 54b. The third utilization unit 3c includes a utilization circuit 13c, an indoor fan 53c, a utilization-side control unit 50c, and an indoor fan motor 54c.
The utilization circuit 13a mainly includes a utilization-side heat exchanger 52a (corresponding to a first heat exchanger), a first utilization pipe 57a, a second utilization pipe 56a, and a utilization-side expansion valve 51a.
The utilization-side heat exchanger 52a is a device for exchanging heat between the refrigerant and the indoor air, and includes, for example, a fin-and-tube heat exchanger including a large number of heat transfer tubes and fins. Further, the utilization unit 3a includes the indoor fan 53a that sucks the indoor air into the utilization unit, exchanges heat with the refrigerant flowing in the utilization-side heat exchanger 52a, and then supplies the indoor air into the room as supply air. The indoor fan 53a is driven by the indoor fan motor 54a. The plurality of utilization-side heat exchangers 52a, 52b, and 52c are connected in parallel to the secondary-side switching mechanism 22, the suction flow path 23, and the cascade heat exchanger 35.
One end of the second utilization pipe 56a is connected to the liquid side (the side opposite to the gas side) of the utilization-side heat exchanger 52a of the first utilization unit 3a. The other end of the second utilization pipe 56a is connected to the second connecting pipe 16a. The utilization-side expansion valve 51a described above is provided in the middle of the second utilization pipe 56a.
The utilization-side expansion valve 51a is an electrically powered expansion valve whose opening degree can be controlled and that performs control and the like of the flow rate of the refrigerant flowing through the utilization-side heat exchanger 52a. The utilization-side expansion valve 51a is provided in the second utilization pipe 56a.
One end of the first utilization pipe 57a is connected to the gas side of the utilization-side heat exchanger 52a of the first utilization unit 3a. In the present embodiment, the first utilization pipe 57a is connected to the utilization-side heat exchanger 52a on the side opposite to the utilization-side expansion valve 51a. The other end of the first utilization pipe 57a is connected to the first connecting pipe 15a.
Further, the utilization unit 3a is provided with various sensors. Specifically, a liquid-side temperature sensor 58a is provided, the sensor detecting the temperature of the refrigerant on the liquid side of the utilization-side heat exchanger 52a. In addition, the utilization unit 3a is provided with an indoor temperature sensor 55a that detects the indoor temperature that is the temperature of the air taken in from the room and before passing through the utilization-side heat exchanger 52a.
The utilization-side control unit 50a controls operation of respective units 51a and 53a (54a) that constitute the utilization unit 3a. Further, the utilization-side control unit 50a includes a processor such as a CPU and a microcomputer, and a memory, which are provided for controlling the utilization unit 3a, and is configured to be able to exchange control signals and the like with a remote controller (not shown), and exchange control signals and the like with the heat source-side control unit 20 and the branch unit control units 60a, 60b, and 60c of the secondary-side unit 4, and with the primary-side control unit 70 of the primary-side unit 5.
(3-2) Branch Unit
The branch units 6a, 6b, and 6c are connected to the utilization units 3a, 3b, and 3c in a one-to-one correspondence, and are installed in a space or the like above a ceiling of a room such as a building. The branch units 6a, 6b, and 6c are each connected to the heat source unit 2 via the connection pipes 7, 8, and 9. The branch units 6a, 6b, and 6c respectively include branch circuits 14a, 14b, and 14c constituting a part of the secondary-side refrigerant circuit 10.
Next, configurations of the branch units 6a, 6b, and 6c are described. Note that, because the second branch unit 6b and the third branch unit 6c have the similar configuration with the first branch unit 6a, only the configuration of the first branch unit 6a is described herein. For the configurations of the second branch unit 6b and the third branch unit 6c, instead of a suffix “a” indicating each part of the first branch unit 6a, a suffix “b” or “c” is added, respectively, and the description of each part is omitted.
The first branch unit 6a mainly includes the branch circuit 14a constituting a part of the secondary-side refrigerant circuit 10, and the branch unit control unit 60a. In addition, the second branch unit 6b includes the branch circuit 14b and the branch unit control unit 60b. The third branch unit 6c includes the branch circuit 14c and the branch unit control unit 60c.
The branch circuit 14a mainly includes a junction pipe 62a, a first branch pipe 63a, a second branch pipe 64a, a first control valve 66a, a second control valve 67a, and a third branch pipe 61a.
One end of the junction pipe 62a is connected to the first connecting pipe 15a. The other end of the junction pipe 62a is connected to the first branch pipe 63a and the second branch pipe 64a that are branched from the junction pipe.
The first branch pipe 63a is connected to the first connection pipe 8 on the side opposite to the side of the junction pipe 62. The first branch pipe 63a is provided with the first control valve 66a that can be opened and closed. Note that an electrically powered expansion valve whose opening degree can be controlled is adopted herein as the first control valve 66a, but an electromagnetic valve that can only be opened and closed may be adopted.
The second branch pipe 64a is connected to the second connection pipe 9 on the side opposite to the side of the junction pipe 62. The second branch pipe 64a is provided with the second control valve 67a that can be opened and closed. Note that an electrically powered expansion valve whose opening degree can be controlled is adopted herein as the second control valve 67a, but an electromagnetic valve that can only be opened and closed may be adopted.
One end of the third branch pipe 61a is connected to the second connecting pipe 16a. The other end of the third branch pipe 61a is connected to the third connection pipe 7.
Further, the first branch unit 6a can function as follows by opening the first control valve 66a and the second control valve 67a when the cooling operation to be described later is performed. The first branch unit 6a sends the refrigerant flowing into the third branch pipe 61a through the third connection pipe 7 to the second connecting pipe 16a. Note that the refrigerant flowing through the second utilization pipe 56a of the first utilization unit 3a through the second connecting pipe 16a is sent to the utilization-side heat exchanger 52a of the first utilization unit 3a through the utilization-side expansion valve Ma. Then, the refrigerant sent to the utilization-side heat exchanger 52a evaporates by heat exchange with the indoor air, and then flows through the first connecting pipe 15a via the first utilization pipe 57a. The refrigerant having flowed through the first connecting pipe 15a is sent to the junction pipe 62a of the first branch unit 6a. The refrigerant having flowed through the junction pipe 62a branches and flows into the first branch pipe 63a and the second branch pipe 64a. The refrigerant having passed through the first control valve 66a in the first branch pipe 63a is sent to the first connection pipe 8. The refrigerant having passed through the second control valve 67a in the second branch pipe 64a is sent to the second connection pipe 9.
In addition, the first branch unit 6a can function as follows by bringing the first control valve 66a into the closed state and the second control valve 67a into the open state in the case of cooling the room by the first utilization unit 3a at the time of performing the cooling dominant operation and the heating dominant operation to be described later. The first branch unit 6a sends the refrigerant flowing into the third branch pipe 61a through the third connection pipe 7 to the second connecting pipe 16a. Note that the refrigerant flowing through the second utilization pipe 56a of the first utilization unit 3a through the second connecting pipe 16a is sent to the utilization-side heat exchanger 52a of the first utilization unit 3a through the utilization-side expansion valve Ma. Then, the refrigerant sent to the utilization-side heat exchanger 52a evaporates by heat exchange with the indoor air, and then flows through the first connecting pipe 15a via the first utilization pipe 57a. The refrigerant having flowed through the first connecting pipe 15a is sent to the junction pipe 62a of the first branch unit 6a. The refrigerant having flowed through the junction pipe 62a flows into the second branch pipe 64a, passes through the second control valve 67a, and is sent to the second connection pipe 9.
Further, the first branch unit 6a can function as follows by bringing the second control valve 67a into the open state or the close state according to the operation condition as described later and bringing the first control valve 66a into the close state at the time of performing the heating operation. In the first branch unit 6a, the refrigerant flowing into the first branch pipe 63a through the first connection pipe 8 passes through the first control valve 66a and is sent to the junction pipe 62a. The refrigerant having flowed through the junction pipe 62a flows through the first utilization pipe 57a of the utilization unit 3a via the first connecting pipe 15a, and is sent to the utilization-side heat exchanger 52a. Then, the refrigerant sent to the utilization-side heat exchanger 52a evaporates by heat exchange with the indoor air, and then passes through the utilization-side expansion valve 51a provided in the second utilization pipe 56a. The refrigerant having passed through the second utilization pipe 56a flows through the third branch pipe 61a of the first branch unit 6a via the second connecting pipe 16a, and is sent to the third connection pipe 7.
In addition, the first branch unit 6a can function as follows by bringing the second control valve 67a into the close state and the first control valve 66a into the open state in the case of heating the room by the first utilization unit 3a at the time of performing the cooling dominant operation and the heating dominant operation to be described later. In the first branch unit 6a, the refrigerant flowing into the first branch pipe 63a through the first connection pipe 8 passes through the first control valve 66a and is sent to the junction pipe 62a. The refrigerant having flowed through the junction pipe 62a flows through the first utilization pipe 57a of the utilization unit 3a via the first connecting pipe 15a, and is sent to the utilization-side heat exchanger 52a. Then, the refrigerant sent to the utilization-side heat exchanger 52a evaporates by heat exchange with the indoor air, and then passes through the utilization-side expansion valve 51a provided in the second utilization pipe 56a. The refrigerant having passed through the second utilization pipe 56a flows through the third branch pipe 61a of the first branch unit 6a via the second connecting pipe 16a, and is sent to the third connection pipe 7.
The above function is provided not only in the first branch unit 6a but also in the second branch unit 6b and the third branch unit 6c. Therefore, each of the first branch unit 6a, the second branch unit 6b, and the third branch unit 6c can individually switch whether each of the utilization-side heat exchangers 52a, 52b, and 52c functions as the evaporator for the refrigerant or the radiator for the refrigerant.
The branch unit control unit 60a controls operation of respective units 66a and 67a that constitute the branch unit 6a. Further, the branch unit control unit 60a includes a processor such as a CPU and a microcomputer, and a memory, which are provided for controlling the branch unit 6a, and is configured to be able to exchange control signals and the like with a remote controller (not shown), and exchange control signals and the like with the heat source-side control unit 20 and the utilization units 3a, 3b, and 3c of the secondary-side unit 4, and with the primary-side control unit 70 of the primary-side unit 5.
(3-3) Heat Source Unit
The heat source unit 2 is installed in a space different from a space in which the utilization units 3a, 3b, and 3c and the branch units 6a, 6b, and 6c are disposed, on a rooftop, or the like. The heat source unit 2 is connected to the branch units 6a, 6b, 6c via the connection pipes 7, 8, and 9, and constitutes a part of the secondary-side refrigerant circuit 10.
Next, a configuration of the heat source unit 2 is described. The heat source unit 2 mainly includes a heat source circuit 12 and the heat source-side control unit 20 that constitute a part of the secondary-side refrigerant circuit 10.
The heat source circuit 12 mainly includes a secondary-side compressor 21 (corresponding to a first compressor), the secondary-side switching mechanism 22 (corresponding to a switching mechanism), a first heat source pipe 28, a second heat source pipe 29, the suction flow path 23 (corresponding to a third flow path), a discharge flow path 24, the third heat source pipe 25 (corresponding to a first flow path), the fourth heat source pipe 26 (corresponding to a second flow path), a fifth heat source pipe 27, the cascade heat exchanger 35, the secondary-side expansion valve 36 (corresponding to a first expansion valve), a third shut-off valve 31, a first shut-off valve 32, a second shut-off valve 33, an accumulator 30, an oil separator 34, an oil return circuit 40, a connection flow path 45, and a bypass flow path 47. Note that the heat source circuit 12 may be the one that does not include, between the cascade heat exchanger 35 and the third shut-off valve 31, a refrigerant container such as a receiver that stores the secondary-side refrigerant.
The secondary-side compressor 21 is a device for compressing the secondary-side refrigerant, and includes, for example, a scroll type or other positive displacement compressor whose operating capacity can be varied by inverter-controlling a compressor motor 21a. Note that the secondary-side compressor 21 is controlled to cause the operating capacity to increase as the load increases, according to the load during operation. In addition, the secondary-side compressor 21 may be used, the compressor having a structure in which the refrigerant cannot or substantially cannot move back and forth between the discharge side and the suction side during the stop.
The secondary-side switching mechanism 22 is a mechanism that can switch the connection state of the secondary-side refrigerant circuit 10, particularly, the flow path of the refrigerant in the heat source circuit 12. In the present embodiment, the secondary-side switching mechanism 22 is configured by aligning four switching valves 22a, 22b, 22c, and 22d, which are two-way valves, in an annular flow path. Alternatively, a combination of a plurality of three-way switching valves may be used as the secondary-side switching mechanism 22. The secondary-side switching mechanism 22 includes the first switching valve 22a provided in a flow path connecting the discharge flow path 24 to the third heat source pipe 25, the second switching valve 22b provided in a flow path connecting the discharge flow path 24 to the first heat source pipe 28, the third switching valve 22c provided in a flow path connecting the suction flow path 23 to third heat source pipe 25, and the fourth switching valve 22d provided in a flow path connecting the suction flow path 23 to the first heat source pipe 28. In the present embodiment, the first switching valve 22a, the second switching valve 22b, the third switching valve 22c, and the fourth switching valve 22d are electromagnetic valves that are switched between an open state and a close state.
Further, in the case where the cascade heat exchanger 35 is made to function as a radiator for the secondary-side refrigerant, the secondary-side switching mechanism 22 is brought into a first connection state where the first switching valve 22a is brought into the open state and the discharge side of the secondary-side compressor 21 is connected to the gas side of the secondary-side flow path 35a of the cascade heat exchanger 35, and meanwhile, the third switching valve 22c is brought into the close state. Further, in the case where the cascade heat exchanger 35 is made to function as an evaporator for the secondary-side refrigerant, the secondary-side switching mechanism 22 is brought into a second connection state where the third switching valve 22c is brought into the open state and the suction side of the secondary-side compressor 21 is connected to the gas side of the secondary-side flow path 35a of the cascade heat exchanger 35, and meanwhile, the first switching valve 22a is brought into the close state. Further, in the case where the secondary-side refrigerant discharged from the secondary-side compressor 21 is sent to the first connection pipe 8, the secondary-side switching mechanism 22 is brought into a third connection state where the second switching valve 22b is brought into the open state and the discharge side of the secondary-side compressor 21 is connected to the first connection pipe 8, and meanwhile, the fourth switching valve 22d is brought into the close state. Further, in the case where the refrigerant flowing through the first connection pipe 8 is sucked into the secondary-side compressor 21, the secondary-side switching mechanism 22 is brought into a fourth connection state where the fourth switching valve 22d is brought into the open state and the first connection pipe 8 is connected to the suction side of the secondary-side compressor 21, and meanwhile, the second switching valve 22b is brought into the close state.
The cascade heat exchanger 35 is a device for performing heat exchange between the refrigerant such as R32, which is the primary-side refrigerant, and carbon dioxide, which is the secondary-side refrigerant, without mixing the refrigerants with each other. The cascade heat exchanger 35 includes the secondary-side flow path 35a through which the secondary-side refrigerant of the secondary-side refrigerant circuit 10 flows, and the primary-side flow path 35b through which the primary-side refrigerant of the primary-side refrigerant circuit 5a flows, and thus is shared by the primary-side unit 5 and the heat source unit 2. In addition, in the present embodiment, the cascade heat exchanger 35 is disposed inside a not-shown casing of the heat source unit 2, and refrigerant pipes extending from both ends of the primary-side flow path 35b of the cascade heat exchanger 35 are provided so as to extend to the outside of the not-shown casing of the heat source unit 2.
The secondary-side expansion valve 36 is an electrically powered expansion valve whose opening degree can be controlled and is connected to the cascade heat exchanger 35 on the liquid side in order to perform control and the like of the flow rate of the secondary-side refrigerant flowing through the cascade heat exchanger 35.
The third shut-off valve 31, the first shut-off valve 32, and the second shut-off valve 33 are valves provided in corresponding connecting ports connected with external devices and pipes (specifically, the connection pipes 7, 8, and 9). Specifically, the third shut-off valve 31 is connected to the third connection pipe 7 drawn out from the heat source unit 2. The first shut-off valve 32 is connected to the first connection pipe 8 drawn out from the heat source unit 2. The second shut-off valve 33 is connected to the second connection pipe 9 drawn out from the heat source unit 2.
The first heat source pipe 28 is a refrigerant pipe that connects the first shut-off valve 32 to the secondary-side switching mechanism 22. Specifically, the first heat source pipe 28 connects the first shut-off valve 32 to a portion of the secondary-side switching mechanism 22 between the second switching valve 22b and the fourth switching valve 22d.
The suction flow path 23 is a flow path that connects the secondary-side switching mechanism 22 and the suction side of the secondary-side compressor 21. Specifically, the suction flow path 23 connects a portion of the secondary-side switching mechanism 22 between the third switching valve 22c and the fourth switching valve 22d to the suction side of the secondary-side compressor 21. The suction flow path 23 is provided in the middle with the accumulator 30.
The second heat source pipe 29 is a refrigerant pipe that connects the second shut-off valve 33 to the middle of the suction flow path 23. In addition, in the present embodiment, the second heat source pipe 29 is connected to the suction flow path 23 at a connection point Y which is a portion in the suction flow path 23 between the accumulator 30 and a portion between the second switching valve 22b and the fourth switching valve 22d in the secondary-side switching mechanism 22.
The discharge flow path 24 is a refrigerant pipe that connects the discharge side of the secondary-side compressor 21 to the secondary-side switching mechanism 22. Specifically, the discharge flow path 24 connects the discharge side of the secondary-side compressor 21 to a portion of the secondary-side switching mechanism 22 between the first switching valve 22a and the second switching valve 22b.
The third heat source pipe 25 is a refrigerant pipe that connects the secondary-side switching mechanism 22 to the gas side of the cascade heat exchanger 35. Specifically, the third heat source pipe 25 connects a portion of the secondary-side switching mechanism 22 between first switching valve 22a and the third switching valve 22c to the gas-side end of the secondary-side flow path 35a in the cascade heat exchanger 35.
The fourth heat source pipe 26 is a refrigerant pipe that connects the liquid side (the side opposite to the gas side, the side opposite to the side on which the secondary-side switching mechanism 22 is provided) of the cascade heat exchanger 35 to the secondary-side expansion valve 36. Specifically, the fourth heat source pipe 26 connects the liquid-side end (the end on the side opposite to the gas side) of the secondary-side flow path 35a in the cascade heat exchanger 35 to the secondary-side expansion valve 36.
The fifth heat source pipe 27 is a refrigerant pipe that connects the secondary-side expansion valve 36 to the third shut-off valve 31.
The accumulator 30 is a container that can store the secondary-side refrigerant, and is provided on the suction side of the secondary-side compressor 21.
The oil separator 34 is provided in the middle of the discharge flow path 24. The oil separator 34 is a device for separating a refrigerating machine oil from the secondary-side refrigerant, the oil being discharged from the secondary-side compressor 21 along with the secondary-side refrigerant, and for returning the oil to the secondary-side compressor 21.
The oil return circuit 40 is provided to connect the oil separator 34 to the suction flow path 23. The oil return circuit 40 includes an oil return flow path 41 in which a flow path extending from the oil separator 34 extends to join a portion of the suction flow path 23 between the accumulator 30 and the suction side of the secondary-side compressor 21. The oil return flow path 41 is provided in the middle with an oil return capillary tube 42 and an oil return on-off valve 44. By the oil return on-off valve 44 being controlled to be opened, the refrigerating machine oil separated in the oil separator 34 passes through the oil return capillary tube 42 of the oil return flow path 41 and is returned to the suction side of the secondary-side compressor 21. In the present embodiment, when the secondary-side compressor 21 is in the operating state in the secondary-side refrigerant circuit 10, the oil return on-off valve 44 repeats keeping the open state for a predetermined time and keeping the close state for a predetermined time, thereby controlling the amount of refrigerating machine oil returned through the oil return circuit 40. Note that, in the present embodiment, the oil return on-off valve 44 is an electromagnetic valve that is controlled to open and close, but a configuration may be adopted in which the oil return on-off valve 44 is an electrically powered expansion valve whose opening degree can be controlled, and meanwhile, the oil return capillary tube 42 is omitted.
The connection flow path 45 is provided to connect the fifth heat source pipe 27 to the suction flow path 23. The connection flow path 45 is provided to connect the fifth heat source pipe 27 and a portion of the suction flow path 23 between the secondary-side switching mechanism 22 and the accumulator 30. The connection flow path 45 is provided in the middle with a connection on-off valve 46. Note that, in the present embodiment, the connection on-off valve 46 is an electromagnetic valve that is controlled to open and close, but the connection on-off valve 46 may be an electrically powered expansion valve whose opening degree can be controlled. In the present embodiment, the connection on-off valve 46 is controlled to be opened during the stop of the cooling operation or the cooling dominant operation to be described later, and is kept closed during the normal operation when the secondary-side compressor 21 is driven. As described above, the pressure of the high-pressure refrigerant in the secondary-side refrigerant circuit 10 is reduced by bringing the connection on-off valve 46 to the open state during the stop of the cooling operation or the cooling dominant operation. As a result, during the stop of the secondary-side compressor 21, the pressure of the high-pressure refrigerant is prevented from becoming too high due to an increase in the temperature around the location where the high-pressure refrigerant is present in the secondary-side refrigerant circuit 10.
The bypass flow path 47 is provided to connect the third heat source pipe 25 to the suction flow path 23. The bypass flow path 47 is provided to connect the third heat source pipe 25 to a portion of the suction flow path 23 between the secondary-side switching mechanism 22 and the accumulator 30. The bypass flow path 47 is provided in the middle with a bypass capillary tube 48 (corresponding to a decompression mechanism) and a bypass on-off valve 49 (corresponding to an on-off valve). In the present embodiment, the bypass on-off valve 49 is controlled to be opened at the start of the heating operation or the heating dominant operation to be described later, and is kept closed during the normal operation when the secondary-side compressor 21 is driven. Note that, in the present embodiment, the bypass on-off valve 49 is an electromagnetic valve that is controlled to open and close, but a configuration may be adopted in which the bypass on-off valve 49 is an electrically powered expansion valve whose opening degree can be controlled, and meanwhile, the bypass capillary tube 48 is omitted.
Further, the heat source unit 2 is provided with various sensors. Specifically, there is provided a secondary-side suction pressure sensor 37 (corresponding to a sensor that detects the refrigerant pressure or the refrigerant temperature in the third flow path) that detects the pressure of the secondary-side refrigerant on the suction side of the secondary-side compressor 21, a secondary-side discharge pressure sensor 38 that detects the pressure of the secondary-side refrigerant on the discharge side of the secondary-side compressor 21, and a secondary-side discharge temperature sensor 39 that detects the temperature of the secondary-side refrigerant on the discharge side of the secondary-side compressor 21.
The heat source-side control unit 20 controls operation of the respective units 21 (21a), 22, 36, 44, 46, and 49 that constitute the heat source unit 2. Further, the heat source-side control unit 20 includes a processor such as a CPU and a microcomputer, and a memory, which are provided for controlling the heat source unit 2, and is configured to be able to exchange control signals and the like with the primary-side control unit 70 of the primary-side unit 5, utilization-side control units 50a, 50b, and 50c of the utilization units 3a, 3b, and 3c, and the branch unit control units 60a, 60b, and 60c.
In the refrigeration cycle system 1, the heat source-side control unit 20, the utilization-side control units 50a, 50b, and 50c, the branch unit control units 60a, 60b, and 60c, and the primary-side control unit 70, which are described above, are communicably connected to each other in a wired or wireless manner to constitute a control unit 80. Therefore, this control unit 80 controls the operation of the respective units 21 (21a), 22, 36, 44, 46, 49, 51a, 51b, 51c, 53a, 53b, 53c (54a, 54b, 54c), 66a, 66b, 66c, 67a, 67b, 67c, 71 (71a), 72, 75 (75a), and 76 on the basis of detection information of the various sensors such as 37, 38, 39, 77, 78, 58a, 58b, and 58c and instruction information or the like received from a not-shown remote controller or the like.
Next, the operation of the refrigeration cycle system 1 is described with reference to
The refrigeration cycle operation of the refrigeration cycle system 1 can be mainly classified into the cooling operation, the heating operation, the cooling dominant operation, and the heating dominant operation.
Here, the cooling operation is a refrigeration cycle operation in which only the utilization unit whose utilization-side heat exchanger functions as an evaporator for the refrigerant is available, and the cascade heat exchanger 35 is made to function as a radiator for the secondary-side refrigerant with respect to the evaporation load of the entire utilization unit.
The heating operation is a refrigeration cycle operation in which only the utilization unit whose utilization-side heat exchanger functions as a radiator for the refrigerant is available, and the cascade heat exchanger 35 is made to function as an evaporator for the secondary-side refrigerant with respect to the radiation load of the entire utilization unit.
The cooling dominant operation is an operation that uses, in combination, a utilization unit whose utilization-side heat exchanger functions as an evaporator for the refrigerant and a utilization unit whose utilization-side heat exchanger functions as a radiator for the refrigerant. The cooling dominant operation is a refrigeration cycle operation in which, in a case where the evaporation load is dominant among the heat load of the entire utilization unit, the cascade heat exchanger 35 is made to function as a radiator for the secondary-side refrigerant.
The heating dominant operation is an operation that uses, in combination, a utilization unit whose utilization-side heat exchanger functions as an evaporator for the refrigerant and a utilization unit whose utilization-side heat exchanger functions as a radiator for the refrigerant. The heating dominant operation is a refrigeration cycle operation in which, in a case where the radiation load is dominant among the heat load of the entire utilization unit, the cascade heat exchanger 35 is made to function as an evaporator for the secondary-side refrigerant.
Note that the operation of the refrigeration cycle system 1 including these refrigeration cycle operations is performed by the above-described control unit 80.
In any of these operations, any of the utilization units may be in an operation stop state. The utilization-side control units 50a, 50b, and 50c having received a command from a not-shown remote controller or the like control the utilization units 3a, 3b, and 3c to be in the operation stop state. In the operation stop state, the utilization units 3a, 3b, and 3c close the utilization-side expansion valves 51a, 51b, and 51c or close the first control valves 66a, 66b, and 66c and the second control valves 67a, 67b, and 67c before the indoor fans 53a, 53b, and 53c are stopped. As a result, the flow of the refrigerant in the utilization units 3a, 3b, and 3c in the operation stop state is stopped.
(5-1) Cooling Operation
In the cooling operation, all of the utilization-side heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c are operated to function as evaporators for the refrigerant, and the cascade heat exchanger 35 is operated to functions as a radiator for the secondary-side refrigerant. In this cooling operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1 are configured as shown in
Specifically, in the primary-side unit 5, the primary-side switching mechanism 72 is switched to the fifth connection state to cause the cascade heat exchanger 35 to function as an evaporator for the primary-side refrigerant. Note that the fifth connection state of the primary-side switching mechanism 72 is a connection state indicated by a solid line in the primary-side switching mechanism 72 in
In addition, in the heat source unit 2, the secondary-side switching mechanism 22 in the first connection state is switched to the fourth connection state to cause the cascade heat exchanger 35 to function as a radiator for the secondary-side refrigerant. Note that the first connection state of the secondary-side switching mechanism 22 is a connection state in which the first switching valve 22a is in the open state and the third switching valve 22c is in the close state. The fourth connection state of the secondary-side switching mechanism 22 is a connection state in which the fourth switching valve 22d is in the open state and the second switching valve 22b is in the close state. Here, the opening degree of the secondary-side expansion valve 36 is controlled. In the first to third utilization units 3a, 3b, and 3c, the first control valves 66a, 66b, and 66c and the second control valves 67a, 67b, and 67c are controlled to be opened. As a result, all of the utilization-side heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c function as evaporators for the refrigerant. Further, all of the utilization-side heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c are in the connected state to the suction side of the secondary-side compressor 21 of the heat source unit 2 via the first utilization pipes 57a, 57b, and 57c, the first connecting pipes 15a, 15b, and 15c, the junction pipes 62a, 62b, and 62c, the first branch pipes 63a, 63b, and 63c, the second branch pipes 64a, 64b, and 64c, the first connection pipe 8, and the second connection pipe 9. In the utilization units 3a, 3b, and 3c, the opening degrees of the utilization-side expansion valves 51a, 51b, and 51c are controlled. Note that, in the cooling operation, the plurality of utilization units 3a, 3b, and 3c may include the utilization unit in the operation stop state.
In the secondary-side refrigerant circuit 10 as described above, the high-pressure secondary-side refrigerant compressed and discharged by the secondary-side compressor 21 is sent to the secondary-side flow path 35a of the cascade heat exchanger 35 through the secondary-side switching mechanism 22. In the cascade heat exchanger 35, the high-pressure secondary-side refrigerant flowing through the secondary-side flow path 35a radiates heat, and the primary-side refrigerant flowing through the primary-side flow path 35b of the cascade heat exchanger 35 evaporates. The secondary-side refrigerant that has dissipated heat in the cascade heat exchanger 35 passes through the secondary-side expansion valve 36 whose opening degree is controlled, and then is sent to the third connection pipe 7 through the third shut-off valve 31.
Then, the refrigerant sent to the third connection pipe 7 is branched into three and passes through the third branch pipes 61a, 61b, and 61c of the first to third branch units 6a 6b, and 6c. Thereafter, the refrigerant having flowed through the second connecting pipes 16a, 16b, and 16c is sent to the second utilization pipes 56a, 56b, and 56c of the first to third utilization units 3a, 3b, and 3c. The refrigerant sent to the second utilization pipes 56a, 56b, and 56c is sent to the utilization-side expansion valves 51a, 51b, and 51c of the utilization units 3a, 3b, and 3c.
Then, the refrigerant having passed through the utilization-side expansion valves 51a, 51b, and 51c whose opening degrees are controlled exchanges heat with the indoor air supplied by the indoor fans 53a, 53b, and 53c in the utilization-side heat exchangers 52a, 52b, and 52c. As a result, the refrigerant flowing through the utilization-side heat exchangers 52a, 52b, and 52c evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and is supplied into the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the utilization-side heat exchangers 52a, 52b, and 52c flows through the first utilization pipes 57a, 57b, and 57c, flows through the first connecting pipes 15a, 15b, and 15c, and then is sent to the junction pipes 62a, 62b, and 62c of the first to third branch units 6a, 6b, and 6c.
Then, the low-pressure gas refrigerant sent to the junction pipes 62a, 62b, and 62c branches and flows into the first branch pipes 63a, 63b, and 63c and the second branch pipes 64a, 64b, and 64c. The refrigerant having passed through the first control valve 66a, 66b, and 66c in the first branch pipe 63a, 63b, and 63c is sent to the first connection pipe 8. The refrigerant having passed through the second control valve 67a, 67b, and 67c in the second branch pipe 64a, 64b, and 64c is sent to the second connection pipe 9.
Thereafter, the low-pressure gas refrigerant sent to the first connection pipe 8 and the second connection pipe 9 is returned to the suction side of the secondary-side compressor 21 through the first shut-off valve 32, the second shut-off valve 33, the first heat source pipe 28, the second heat source pipe 29, the secondary-side switching mechanism 22, the suction flow path 23, and the accumulator 30.
In this manner, the cooling operation is performed.
(5-2) Heating Operation
In the heating operation, for example, all of the utilization-side heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c function as radiators for the refrigerant. In the heating operation, the cascade heat exchanger 35 functions as an evaporator for the secondary-side refrigerant. In the heating operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1 are configured as shown in
Specifically, in the primary-side unit 5, the primary-side switching mechanism 72 is switched to a sixth connection state to cause the cascade heat exchanger 35 to function as a radiator for the primary-side refrigerant. The sixth connection state of the primary-side switching mechanism 72 is a connection state indicated by a broken line in the primary-side switching mechanism 72 in
In addition, in the heat source unit 2, the secondary-side switching mechanism 22 in the second connection state is switched to the third connection state. The cascade heat exchanger 35 is thus made to function as an evaporator for the secondary-side refrigerant. The second connection state of the secondary-side switching mechanism 22 is a connection state in which the first switching valve 22a is in the close state and the third switching valve 22c is in the open state. The third connection state of the secondary-side switching mechanism 22 is a connection state in which the second switching valve 22b is in the open state and the fourth switching valve 22d is in the close state. In addition, the opening degree of the secondary-side expansion valve 36 is controlled. In the first to third branch units 6a, 6b, and 6c, the first control valves 66a, 66b, and 66c are controlled to be opened and the second control valves 67a, 67b, and 67c are controlled to be closed. As a result, all of the utilization-side heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c function as radiators for the refrigerant. Further, the utilization-side heat exchangers 52a, 52b, and 52c of the utilization units 3a, 3b, and 3c are in the connected state to the discharge side of the secondary-side compressor 21 of the heat source unit 2 via the discharge flow path 24, the first heat source pipe 28, the first connection pipe 8, the first branch pipes 63a, 63b, and 63c, the junction pipes 62a, 62b, and 62c, the first connecting pipes 15a, 15b, and 15c, and the first utilization pipes 57a, 57b, and 57c. In the utilization units 3a, 3b, and 3c, the opening degrees of the utilization-side expansion valves Ma, Mb, and Mc are controlled. Note that, in the heating operation, the plurality of utilization units 3a, 3b, and 3c may include the utilization unit in the operation stop state.
In the secondary-side refrigerant circuit 10 as described above, the high-pressure refrigerant compressed and discharged by the secondary-side compressor 21 is sent to the first heat source pipe 28 through the second switching valve 22b controlled to be opened in the secondary-side switching mechanism 22. The refrigerant sent to the first heat source pipe 28 is sent to the first connection pipe 8 through the first shut-off valve 32.
Then, the high-pressure refrigerant sent to the first connection pipe 8 is branched into three and sent to the first branch pipes 63a, 63b, and 63c of the utilization units 3a, 3b, and 3c. The high-pressure refrigerant sent to the first branch pipes 63a, 63b, and 63c passes through the first control valves 66a, 66b, and 66c, and flows through the junction pipes 62a, 62b, and 62c. Thereafter, the refrigerant having flowed through the first connecting pipes 15a, 15b, and 15c and the first utilization pipes 57a, 57b, and 57c is sent to the utilization-side heat exchangers 52a, 52b, and 52c.
Then, the high-pressure refrigerant sent to the utilization-side heat exchangers 52a, 52b, and 52c exchanges heat in the utilization-side heat exchangers 52a, 52b, and 52c with the indoor air supplied from the indoor fans 53a, 53b, and 53c. As a result, the refrigerant flowing through the utilization-side heat exchangers 52a, 52b, and 52c radiates heat. The indoor air is heated and is supplied into the room. As a result, the indoor space is heated. Then, the refrigerant having radiated heat in the utilization-side heat exchangers 52a, 52b, and 52c flows through the second utilization pipes 56a, 56b, and 56c, and passes through the utilization-side expansion valves 51a, 51b, and 51c each of whose opening degree is controlled. Thereafter, the refrigerant having flowed through the second connecting pipes 16a, 16b, and 16c flows through the third branch pipes 61a, 61b, and 61c of the respective branch units 6a, 6b, and 6c.
Then, the flows of the refrigerant sent to the third branch pipes 61a, 61b, and 61c are sent to the third connection pipe 7 to be joined together.
The refrigerant then sent to the third connection pipe 7 is sent to the secondary-side expansion valve 36 through the third shut-off valve 31. The refrigerant sent to the secondary-side expansion valve 36 is subjected to flow rate control in the secondary-side expansion valve 36 and is then sent to the cascade heat exchanger 35. In the cascade heat exchanger 35, the secondary-side refrigerant flowing through the secondary-side flow path 35a evaporates to become the low-pressure gas refrigerant and is sent to the secondary-side switching mechanism 22, and the primary-side refrigerant flowing through the primary-side flow path 35b of the cascade heat exchanger 35 condenses. Then, the low-pressure secondary-side gas refrigerant sent to the secondary-side switching mechanism 22 is returned to the suction side of the secondary-side compressor 21 through the suction flow path 23 and the accumulator 30.
In this manner, the heating operation is performed.
(5-3) Cooling Dominant Operation
The cooling dominant operation is an operation in which, for example, the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b function as evaporators for the refrigerant and the utilization-side heat exchanger 52c of the utilization unit 3c functions as a radiator for the refrigerant. In the cooling dominant operation, the cascade heat exchanger 35 functions as a radiator for the secondary-side refrigerant. In this cooling dominant operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1 are configured as shown in
Specifically, in the primary-side unit 5, the primary-side switching mechanism 72 is switched to the fifth connection state (the state indicated by a solid line of the primary-side switching mechanism 72 in
In addition, in the heat source unit 2, the secondary-side switching mechanism 22 in the first connection state (in which the first switching valve 22a is in the open state and the third switching valve 22c is in the close state) is switched to the third connection state (in which the second switching valve 22b is in the open state and the fourth switching valve 22d is in the close state) to cause the cascade heat exchanger 35 to function as a radiator for the secondary-side refrigerant. In addition, the opening degree of the secondary-side expansion valve 36 is controlled. In the first to third branch units 6a, 6b, and 6c, the first control valve 66c and the second control valves 67a and 67b are controlled to be opened, and the first control valves 66a and 66b and the second control valve 67c are controlled to be closed. As a result, the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b function as evaporators for the refrigerant and the utilization-side heat exchanger 52c of the utilization unit 3c functions as a radiator for the refrigerant. Further, the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b are in the connected state to the suction side of the secondary-side compressor 21 of the heat source unit 2 via the second connection pipe 9, and the utilization-side heat exchanger 52c of the utilization unit 3c is in the connected state to the discharge side of the secondary-side compressor 21 of the heat source unit 2 via the first connection pipe 8. In the utilization units 3a, 3b, and 3c, the opening degrees of the utilization-side expansion valves 51a, 51b, and 51c are controlled. Note that, in the cooling dominant operation, the plurality of utilization units 3a, 3b, and 3c may include the utilization unit in the operation stop state.
In the above configured secondary-side refrigerant circuit 10, a part of the high-pressure secondary-side refrigerant compressed and discharged by the secondary-side compressor 21 is sent to the first connection pipe 8 through the secondary-side switching mechanism 22, the first heat source pipe 28, and the first shut-off valve 32, and the rest of the refrigerant is sent to the secondary-side flow path 35a of the cascade heat exchanger 35 through the secondary-side switching mechanism 22 and the third heat source pipe 25.
Then, the high-pressure refrigerant sent to the first connection pipe 8 is sent to the first branch pipe 63c. The high-pressure refrigerant sent to the first branch pipe 63c is sent to the utilization-side heat exchanger 52c of the utilization unit 3c through the first control valve 66c and the junction pipe 62c.
Then, the high-pressure refrigerant sent to the utilization-side heat exchanger 52c exchanges heat in the utilization-side heat exchanger 52c with the indoor air supplied from the indoor fan 53c. As a result, the refrigerant flowing through the utilization-side heat exchangers 52c radiates heat. The indoor air is heated and supplied into the room, and the heating operation of the utilization unit 3c is performed. The refrigerant having dissipated heat in the utilization-side heat exchanger 52c flows through the second utilization pipe 56c, and is subjected to flow rate control in the utilization-side expansion valve 51c. Thereafter, the refrigerant having flowed through the second connecting pipe 16c is sent to the third branch pipe 61c of the branch unit 6c.
Then, the refrigerant sent to the third branch pipe 61c is sent to the third connection pipe 7.
Further, the high-pressure refrigerant sent to the secondary-side flow path 35a of the cascade heat exchanger 35 radiates heat in the cascade heat exchanger 35 by exchanging heat with the primary-side refrigerant flowing through the primary-side flow path 35b. The secondary-side refrigerant having dissipated heat in the cascade heat exchanger 35 is subjected to flow rate control in the secondary-side expansion valve 36, and then is sent to the third connection pipe 7 through the third shut-off valve 31, and joins the refrigerant having dissipated heat in the utilization-side heat exchanger 52c.
Then, the refrigerant joined in the third connection pipe 7 is branched into two and is sent to the third branch pipes 61a and 61b of the branch units 6a and 6b. Thereafter, the refrigerant having flowed through the second connecting pipes 16a and 16b is sent to the second utilization pipes 56a and 56b of the first and second utilization units 3a and 3b. The refrigerant flowing through the second utilization pipes 56a and 56b is sent to the utilization-side expansion valves 51a and 51b of the utilization units 3a and 3b.
Then, the refrigerant having passed through the utilization-side expansion valves 51a and 51b whose opening degrees are controlled exchanges heat in the utilization-side heat exchangers 52a and 52b with the indoor air supplied by the indoor fans 53a and 53b. As a result, the refrigerant flowing through the utilization-side heat exchangers 52a and 52b evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and is supplied into the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant evaporated in the utilization-side heat exchangers 52a and 52b is sent to the junction pipes 62a and 62b of the first and second branch units 6a and 6b.
Then, the flows of the low-pressure gas refrigerant sent to the junction pipes 62a and 62b are sent to the second connection pipe 9 through the second control valves 67a and 67b and the second branch pipes 64a and 64b to be joined together.
Thereafter, the low-pressure gas refrigerant sent to the second connection pipe 9 is returned to the suction side of the secondary-side compressor 21 through the second shut-off valve 33, the second heat source pipe 29, the suction flow path 23, and the accumulator 30.
In this manner, the cooling dominant operation is performed.
(5-4) Heating Dominant Operation
The heating dominant operation is an operation in which, for example, the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b function as radiators for the refrigerant and the utilization-side heat exchanger 52c functions as an evaporator for the refrigerant. In the heating dominant operation, the cascade heat exchanger 35 functions as an evaporator for the secondary-side refrigerant. In the heating dominant operation, the primary-side refrigerant circuit 5a and the secondary-side refrigerant circuit 10 of the refrigeration cycle system 1 are configured as shown in
Specifically, in the primary-side unit 5, the primary-side switching mechanism 72 is switched to the sixth connection state to cause the cascade heat exchanger 35 to function as a radiator for the primary-side refrigerant. The sixth connection state of the primary-side switching mechanism 72 is a connection state indicated by a broken line in the primary-side switching mechanism 72 in
In addition, in the heat source unit 2, the secondary-side switching mechanism 22 in the second connection state is switched to the third connection state. The second connection state of the secondary-side switching mechanism 22 is a connection state in which the first switching valve 22a is in the close state and the third switching valve 22c is in the open state. The third connection state of the secondary-side switching mechanism 22 is a connection state in which the second switching valve 22b is in the open state and the fourth switching valve 22d is in the close state. The cascade heat exchanger 35 is thus made to function as an evaporator for the secondary-side refrigerant. In addition, the opening degree of the secondary-side expansion valve 36 is controlled. In the first to third branch units 6a, 6b, and 6c, the first control valves 66a and 66b and the second control valve 67c are controlled to be opened, and the first control valve 66c and the second control valves 67a and 67b are controlled to be closed. As a result, the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b function as radiators for the refrigerant and the utilization-side heat exchanger 52c of the utilization unit 3c functions as an evaporator for the refrigerant. Further, the utilization-side heat exchanger 52c of the utilization unit 3c is in the connected state to the suction side of the secondary-side compressor 21 of the heat source unit 2 via the first utilization pipe 57c, the first connecting pipe 15c, the junction pipe 62c, the second branch pipe 64c, and the second connection pipe 9. Further, the utilization-side heat exchangers 52a and 52b of the utilization units 3a and 3b are in the connected state to the discharge side of the secondary-side compressor 21 of the heat source unit 2 via the discharge flow path 24, the first heat source pipe 28, the first connection pipe 8, the first branch pipes 63a and 63b, the junction pipes 62a and 62b, the first connecting pipes 15a and 15b, and the first utilization pipes 57a and 57b. In the utilization units 3a, 3b, and 3c, the opening degrees of the utilization-side expansion valves 51a, 51b, and 51c are controlled. Note that, in the heating dominant operation, the plurality of utilization units 3a, 3b, and 3c may include the utilization unit in the operation stop state.
In the secondary-side refrigerant circuit 10 as described above, the high-pressure secondary-side refrigerant compressed and discharged by the secondary-side compressor 21 is sent to the first connection pipe 8 through the secondary-side switching mechanism 22, the first heat source pipe 28, and the first shut-off valve 32.
The high-pressure refrigerant sent to the first connection pipe 8 is then branched into two and sent to the first branch pipes 63a and 63b of the first branch unit 6a and the second branch unit 6b respectively connected to the first utilization unit 3a and the second utilization unit 3b which are the utilization units in operation. The high-pressure refrigerant sent to the first branch pipes 63a and 63b is sent to the utilization-side heat exchangers 52a and 52b of the first utilization unit 3a and the second utilization unit 3b through the first control valves 66a and 66b, the junction pipes 62a and 62b, and the first connecting pipes 15a and 15b.
Then, the high-pressure refrigerant sent to the utilization-side heat exchangers 52a and 52b exchanges heat in the utilization-side heat exchangers 52a and 52b with the indoor air supplied from the indoor fans 53a and 53b. As a result, the refrigerant flowing through the utilization-side heat exchangers 52a and 52b radiates heat. The indoor air is heated and is supplied into the room. As a result, the indoor space is heated. Then, the refrigerant having radiated heat in the utilization-side heat exchangers 52a and 52b flows through the second utilization pipes 56a and 56b, and passes through the utilization-side expansion valves 51a and 51b each of whose opening degree is controlled. The refrigerant having passed through the second connecting pipes 16a and 16b is sent to the third connection pipe 7 via the third branch pipes 61a and 61b of the branch units 6a and 6b.
A part of the refrigerant sent to the third connection pipe 7 is then sent to the third branch pipe 61c of the branch unit 6c, and the rest of the refrigerant is sent to the secondary-side expansion valve 36 through the third shut-off valve 31.
Then, the refrigerant having flowed through the third branch pipe 61c flows through the second utilization pipe 56c of the utilization unit 3c via the second connecting pipe 16c, and is sent to the utilization-side expansion valve 51c.
Then, the refrigerant having passed through the utilization-side expansion valve 51c whose opening degree is controlled exchanges heat in the utilization-side heat exchanger 52c with the indoor air supplied by the indoor fan 53c. As a result, the refrigerant flowing through the utilization-side heat exchanger 52c evaporates and becomes a low-pressure gas refrigerant. The indoor air is cooled and is supplied into the room. As a result, the indoor space is cooled. The low-pressure gas refrigerant having evaporated in the utilization-side heat exchanger 52c passes through the first utilization pipe 57c and the first connecting pipe 15c, and is sent to the junction pipe 62c.
Then, the low-pressure gas refrigerant sent to the junction pipe 62c is sent to the second connection pipe 9 through the second control valve 67c and the second branch pipe 64c.
Thereafter, the low-pressure gas refrigerant sent to the second connection pipe 9 is returned to the suction side of the secondary-side compressor 21 through the second shut-off valve 33, the second heat source pipe 29, the suction flow path 23, and the accumulator 30.
Further, the refrigerant sent to the secondary-side expansion valve 36 passes through the secondary-side expansion valve 36 whose opening degree is controlled, and in the secondary-side flow path 35a in the cascade heat exchanger 35, performs heat exchange with the primary-side refrigerant flowing through the primary-side flow path 35b. As a result, the refrigerant flowing through the secondary-side flow path 35a of the cascade heat exchanger 35 evaporates to become a low-pressure gas refrigerant, and is sent to the secondary-side switching mechanism 22. The low-pressure gas refrigerant sent to the secondary-side switching mechanism 22 joins together in the suction flow path 23 with the low-pressure gas refrigerant evaporated in the utilization-side heat exchanger 52c. The joined refrigerant is returned to the suction side of the secondary-side compressor 21 via the accumulator 30.
In this manner, the heating dominant operation is performed.
Hereinafter, start-up control of the refrigeration cycle system 1 is described with reference to a flowchart in
Here, the start-up control of the heat source unit 2 and the primary-side unit 5 performed at the start of the cooling operation or at the start of the cooling dominant operation is described. The control unit 80 starts the start-up control when a start-up instruction from a not-shown remote controller is received or the like.
In step S1, the control unit 80 controls the connection on-off valve 46, which is in the open state during the stop of the cooling operation or the cooling dominant operation, to be closed.
In step S2, the control unit 80 determines whether or not a first predetermined condition for starting the start-up control is met. Here, the first predetermined condition is not limited, but may be, for example, a condition determined to be satisfied when the temperature of the refrigerant in the suction flow path 23, the outside air temperature, or the like is a predetermined temperature or more. Note that, in the case where the determination is made using the temperature of the refrigerant in the suction flow path 23, a pressure-equivalent saturation temperature derived from the pressure detected by the secondary-side suction pressure sensor 37 may be used. In addition, in the case where the determination is made using the outside air temperature, the temperature detected by the outside air temperature sensor 77 may be used. Here, if the first predetermined condition is satisfied, the process proceeds to step S3. Alternatively, if the first predetermined condition is not satisfied, the process proceeds to step S6.
In step S3, for the primary-side unit 5, the control unit 80 starts the primary-side compressor 71 while bringing the primary-side switching mechanism 72 into the fifth connection state (see the solid line of the primary-side switching mechanism 72 in
In step S4, the control unit 80 determines whether or not a second predetermined condition is met. The second predetermined condition may be a condition satisfied when the pressure detected by the secondary-side suction pressure sensor 37 is a predetermined pressure or less, a condition satisfied when the time elapsed from the start of the process of step S3 exceeds a predetermined time, or a condition satisfied when either or both of the above conditions are satisfied. Here, if the second predetermined condition is satisfied, the process proceeds to step S5. Alternatively, if the second predetermined condition is not satisfied, step S4 is repeated.
In step S5, the control unit 80 starts the secondary-side compressor 21 while setting the connection state of the secondary-side switching mechanism 22 to the connection state corresponding to the cooling operation or the cooling dominant operation described above. In addition, the control unit 80 controls the bypass on-off valve 49 to be closed. The control unit 80 thus ends the start-up control, and thereafter executes the cooling operation or the cooling dominant operation described above.
In step S6, for the primary-side unit 5, the control unit 80 starts the primary-side compressor 71 while bringing the primary-side switching mechanism 72 into the fifth connection state. Further, for the secondary-side unit 4, the control unit 80 starts the secondary-side compressor 21 while keeping the bypass on-off valve 49 closed and setting the connection state of the secondary-side switching mechanism 22 to the connection state corresponding to the cooling operation or the cooling dominant operation described above. The control unit 80 thus ends the start-up control, and thereafter executes the cooling operation or the cooling dominant operation described above.
In the refrigeration cycle system 1 of the present embodiment, carbon dioxide is used as the refrigerant in the secondary-side refrigerant circuit 10. Therefore, the global warming potential (GWP) can be kept low. In addition, even if a refrigerant leak occurs on the utilization side, the refrigerant does not contain chlorofluorocarbon, and thus the chlorofluorocarbon does not flow out on the utilization side. Further, in the refrigeration cycle system 1 of the present embodiment, because the dual refrigeration cycle is adopted, sufficient capacity can be provided in the secondary-side refrigerant circuit 10.
In the refrigeration cycle system 1 according to the present embodiment described above, carbon dioxide is used as the refrigerant in the secondary-side refrigerant circuit 10, but the refrigerant pressure of this carbon dioxide refrigerant rapidly increases easily due to the influence of ambient temperature. In particular, during the stop of the operation and in the case when the ambient temperature such as the outside air temperature becomes a high temperature environment of 30° C. to 40° C. to 50° C., there is a risk that the refrigerant pressure rapidly increases in a region of the high-pressure refrigerant in the secondary-side refrigerant circuit 10. Therefore, in the refrigeration cycle system 1 of the present embodiment, by controlling the connection on-off valve 46 to be opened during the stop of the cooling operation or the cooling dominant operation, the region of the high-pressure refrigerant and the region of the low-pressure refrigerant in the secondary-side refrigerant circuit 10 are connected to reduce the refrigerant pressure of the high-pressure refrigerant.
However, when the connection on-off valve 46 is controlled to be opened during the stop of the operation in this manner and the high-pressure refrigerant is guided to the suction flow path 23, the refrigerant pressure in the suction flow path 23 tends to increase. In this case, when the secondary-side compressor 21 is started, the refrigerant in the suction flow path 23 having a relatively high pressure is further compressed, causing a risk of the refrigerant pressure on the discharge side of the secondary-side compressor 21 rapidly increasing.
On the other hand, in the present embodiment, at the start of the cooling operation or at the start of the cooling dominant operation, the start-up control is performed in which the primary-side compressor 71 is started before the secondary-side compressor 21 is started, and the bypass on-off valve 49 is controlled to be opened. As a result, the primary-side flow path 35b in the cascade heat exchanger 35 functions as an evaporator for the primary-side refrigerant, which allows the temperature of the secondary-side refrigerant in the secondary-side flow path 35a to be lowered. As the temperature of the secondary-side refrigerant in the secondary-side flow path 35a decreases, the refrigerant in the suction flow path 23 can be guided to the secondary-side flow path 35a via the bypass flow path 47 including the bypass capillary tube 48 and the bypass on-off valve 49 controlled to be opened, and the third heat source pipe 25. As a result, the refrigerant pressure on the secondary side in the suction flow path 23 can be suppressed low.
Therefore, even when the secondary-side compressor 21 is started, because the suction refrigerant suppressed to a relatively low pressure is compressed, the refrigerant pressure on the secondary side on the discharge side can also be suppressed low. In addition, the decrease in temperature of the secondary-side refrigerant in the secondary-side flow path 35a of the cascade heat exchanger 35 reduces the pressure of the secondary-side refrigerant in the secondary-side flow path 35a, the third heat source pipe 25, and the fourth heat source pipe 26, which enables the high pressure of the secondary-side refrigerant circuit 10 after the secondary-side compressor 21 is started to be suppressed low.
Note that the heat source circuit 12 of the present embodiment does not include, between the cascade heat exchanger 35 and the third shut-off valve 31, a refrigerant container such as a receiver that stores the secondary-side refrigerant, and has a structure in which the pressure of the high-pressure refrigerant on the secondary side easily increases. However, as described above, in the present embodiment, because the start-up control is performed, an abnormal rise of the high-pressure refrigerant on the secondary side can be avoided.
In the above embodiment, the heat source circuit 12 including the bypass flow path 47 connecting the suction flow path 23 to the third heat source pipe 25 has been described as an example.
In contrast, for example, as shown in
In the above embodiment, the heat source circuit 12 including the bypass flow path 47 connecting the suction flow path 23 to the third heat source pipe 25 has been described as an example.
In contrast, for example, as shown in
The oil return circuit 40a of the present embodiment includes a first oil return flow path 41a and a second oil return flow path 43a that connect the oil separator 34 and the suction flow path 23 in parallel to each other. The first oil return flow path 41a is provided with an oil return capillary tube 42a. The second oil return flow path 43a is provided with an oil return on-off valve 44a. Similarly to the oil return on-off valve 44 of the above embodiment, the oil return on-off valve 44a repeats keeping the open state for a predetermined time and keeping the close state for a predetermined time, thereby controlling the amount of refrigerating machine oil returned through the oil return circuit 40a.
According to the above configuration, by the start-up control, the secondary-side refrigerant in the suction flow path 23 can be guided to the secondary-side flow path 35a in the cascade heat exchanger 35 via the first oil return flow path 41a including the oil return capillary tube 42a, the oil separator 34, the discharge flow path 24, the secondary-side switching mechanism 22 (the first switching valve 22a therein), and the third heat source pipe 25. This configuration can also exhibit similar advantageous effects to those of the above embodiment.
In the above embodiment, the description has been made by exemplifying that, in order to suppress the increase in the pressure of the high-pressure refrigerant in the secondary-side refrigerant circuit 10 during the stop of the operation, the connection on-off valve 46 is controlled to be opened during the stop of the operation and this can cause the pressure of the refrigerant in the suction flow path 23 to be increased.
However, the refrigeration cycle system is not limited to the one in which the connection on-off valve 46 is controlled to be opened during the stop of the system, or the refrigeration cycle system is not limited to the one in which the heat source circuit 12 includes the connection flow path 45 and the connection on-off valve 46.
For example, when the ambient temperature of the suction flow path 23 of the secondary-side refrigerant circuit 10 is relatively high during the stop of the operation, the pressure of the secondary-side refrigerant in the suction flow path 23 tends to increase, and thus a problem similar to that in the above embodiment possibly occurs. In particular, because the accumulator 30 is provided in the middle of the suction flow path 23, the refrigerant in the accumulator 30 is affected by the ambient temperature, which causes the above problem to occur easily. Even in these cases, by performing the process of reducing the refrigerant pressure in the suction flow path 23 before starting the secondary-side compressor 21, an abnormal increase in the pressure of the carbon dioxide refrigerant can be avoided.
In the above embodiment, the primary-side refrigerant circuit 5a through which the refrigerant such as R32 as an example of the heat medium circulates has been described.
In contrast, the heat medium circulating in the primary-side refrigerant circuit 5a is not limited, and for example, brine, water, or the like may be used. The primary-side refrigerant circuit 5a is not limited to the one in which the compression refrigeration cycle as described above is performed, and may be the one in which brine or water as a low-temperature source is supplied to the cascade heat exchanger 35.
In the above embodiment, the description has been made by exemplifying the case where the secondary-side refrigerant circuit 10 includes the secondary-side switching mechanism 22 that causes the cascade heat exchanger 35 to switch between the state of functioning as a radiator for the secondary-side refrigerant and the state of functioning as a heat sink of the secondary-side refrigerant.
In contrast, the secondary-side refrigerant circuit 10 may not include the secondary-side switching mechanism 22 as described above, and may be the one that can operate only to cause the cascade heat exchanger 35 to function as a radiator for the secondary-side refrigerant. In this case, the bypass flow path 47 of the above embodiment may be connected to any location from the utilization-side heat exchangers 52a, 52b, and 52c to the suction side of the secondary-side compressor 21.
In the above embodiment, the description has been made by exemplifying the secondary-side unit 4 including the secondary-side expansion valve 36 provided in the heat source unit 2, the utilization-side expansion valves 51a, 51b, and 51c provided in the utilization units 3a, 3b, and 3c, and the first control valves 66a, 66b, and 66c and the second control valves 67a, 67b, and 67c provided in the branch units 6a, 6b, and 6c.
In contrast, the secondary-side unit 4 of the above embodiment may be configured as, for example, a secondary-side unit 4a shown in
The secondary-side unit 4a is provided with a heat source-side expansion mechanism 11 (corresponding to a first expansion unit) in the heat source unit 2 instead of the secondary-side expansion valve 36 of the above embodiment. The heat source-side expansion mechanism 11 is provided between the fourth heat source pipe 26 and the fifth heat source pipe 27. The heat source-side expansion mechanism 11 includes a first heat source-side branch flow path 11a and a second heat source-side branch flow path 11b that are flow paths aligned in parallel to each other. In the first heat source-side branch flow path 11a, a first heat source-side expansion valve 17a and a first heat source-side check valve 18a are provided side by side. In the second heat source-side branch flow path 11b, a second heat source-side expansion valve 17b and a second heat source-side check valve 18b are provided side by side. Each of the first heat source-side expansion valve 17a and the second heat source-side expansion valve 17b is an electrically powered expansion valve whose opening degree can be controlled. The first heat source-side check valve 18a is a check valve that allows only a flow of the refrigerant flowing from the fourth heat source pipe 26 toward the fifth heat source pipe 27 to pass through. The second heat source-side check valve 18b is a check valve that allows only a flow of the refrigerant flowing from the fifth heat source pipe 27 toward the fourth heat source pipe 26 to pass through. In the above configuration, the opening degree of the first heat source-side expansion valve 17a is controlled when the operation is performed to cause the refrigerant to flow from the fourth heat source pipe 26 toward the fifth heat source pipe 27, and the opening degree of the second heat source-side expansion valve 17b is controlled when the refrigerant is caused to flow from the fifth heat source pipe 27 toward the fourth heat source pipe 26. Specifically, the opening degree of the first heat source-side expansion valve 17a is controlled during the cooling operation and the cooling dominant operation, and the opening degree of the second heat source-side expansion valve 17b is controlled during the heating operation and the heating dominant operation. In the heat source-side expansion mechanism 11 described above, the first heat source-side check valve 18a is connected to the first heat source-side expansion valve 17a, and the second heat source-side check valve 18b is connected to the second heat source-side expansion valve 17b. Therefore, the direction of the flow of the refrigerant passing through the first heat source-side expansion valve 17a can be limited to one direction, and the direction of the flow of the refrigerant passing through the second heat source-side expansion valve 17b can also be limited to one direction. Therefore, even in the case where an expansion valve whose valve opening degree can be controlled to a desired opening degree is difficult to be secured, in a condition where the refrigerant pressure is high or in a condition where the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant is large, the same functional effects as those obtained by the control of the secondary-side expansion valve 36 of the above embodiment can be more reliably obtained.
Here, in the condition where the refrigerant pressure is high or in the condition where the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant is large, the factors that ensure the valve to be controlled to the desired opening degree include the following. Specifically, in the case of using the carbon dioxide refrigerant as the refrigerant for the secondary-side refrigerant circuit 10, the refrigerant is used in a state in which the pressure of the high-pressure refrigerant in the refrigeration cycle is higher than the case of using the conventional refrigerant, such as R32 or R410A. Here, as the expansion valve, the expansion valves that moves a needle with respect to a valve seat to open and close the valve and to control the valve opening degree are used in many cases. At the time of closing the valve or narrowing the valve opening degree, the expansion valve including the needle as described above receives the pressure of the refrigerant at the tip of the needle when the needle is used in a condition where the refrigerant flows in a direction opposite to the direction in which the needle is moved. In this case, because the movement of the needle becomes more suppressed as the refrigerant pressure acting on the tip of the needle increases, there is a risk that the valve opening degree becomes difficult to be controlled to the desired degree. In particular, in the case of using the expansion valve in a direction in which the high-pressure refrigerant acts on the tip side of the needle, and when the difference in the refrigerant pressure between both sides of the expansion valve is large, the valve opening degree cannot be properly closed even if the valve is attempted to be controlled to be fully closed. Therefore, there is a risk that the refrigerant passes between the needle and the valve seat to cause a leak of the refrigerant. In addition, in the case of controlling the expansion valve to have a desired low opening degree, the expansion valve cannot be controlled to have an intended valve opening degree, and as a result, there is a risk that the valve opens more than the desired low opening degree. As described above, in the condition where the refrigerant pressure is high or in the condition where the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant is large, there is a risk that the expansion valve is difficult to be controlled to be in an intended state. On the other hand, in the case of adopting the above-described heat source-side expansion mechanism 11, the above problem can be solved.
The secondary-side unit 4a is provided with, instead of the utilization-side expansion valves Ma, 51b, and 51c, utilization-side expansion mechanisms 151a, 151b, and 151c in the utilization units 3a, 3b, and 3c of the above embodiment. Hereinafter, the first utilization-side expansion mechanism 151a is described. For the configurations of the second utilization-side expansion mechanism 151b and the third utilization-side expansion mechanism 151c, instead of a suffix “a” indicating each part of the first utilization-side expansion mechanism 151a, a suffix “b” or “c” is added, respectively, and the description of each part is omitted. The first utilization-side expansion mechanism 151a is provided in the middle of the second utilization pipe 56a. The first utilization-side expansion mechanism 151a includes a first utilization-side branch flow path 90a and a second utilization-side branch flow path 93a that have flow paths aligned in parallel to each other. In the first utilization-side branch flow path 90a, a first utilization-side expansion valve 91a and a first utilization-side check valve 92a are provided side by side. In the second utilization-side branch flow path 93a, a second utilization-side expansion valve 94a and a second utilization-side check valve 95a are provided side by side. Each of the first utilization-side expansion valve 91a and the second utilization-side expansion valve 94a is an electrically powered expansion valve whose opening degree can be controlled. The first utilization-side check valve 92a is a check valve that allows only a flow of the refrigerant flowing from the second connecting pipe 16a side toward the utilization-side heat exchanger 52a side to pass through. The second utilization-side check valve 95a is a check valve that allows only a flow of the refrigerant flowing from the utilization-side heat exchanger 52a side toward the second connecting pipe 16a side to pass through. In the above configuration, the opening degree of the first utilization-side expansion valve 91a is controlled when the operation is performed to cause the refrigerant to flow from the second connecting pipe 16a side toward the utilization-side heat exchanger 52a side, and the opening degree of the second utilization-side expansion valve 94a is controlled when the refrigerant is caused to flow from the utilization-side heat exchanger 52a side toward the second connecting pipe 16a side. Specifically, the opening degree of the first utilization-side expansion valve 91a is controlled during the cooling operation, during the cooling dominant operation when the utilization-side heat exchanger 52a functions as an evaporator for the refrigerant, and during the heating dominant operation when the utilization-side heat exchanger 52a functions as an evaporator for the refrigerant. The opening degree of the second utilization-side expansion valve 94a is controlled during the heating operation, during the cooling dominant operation when the utilization-side heat exchanger 52a functions as a radiator for the refrigerant, and during the heating dominant operation when the utilization-side heat exchanger 52a functions as a radiator for the refrigerant. In the first utilization-side expansion mechanism 151a described above, the first utilization-side check valve 92a is connected to the first utilization-side expansion valve 91a, and the second utilization-side check valve 95a is connected to the second utilization-side expansion valve 94a. Therefore, the direction of the flow of the refrigerant passing through the first utilization-side expansion valve 91a can be limited to one direction, and the direction of the flow of the refrigerant passing through the second utilization-side expansion valve 94a can also be limited to one direction. Therefore, even in the case where an expansion valve whose opening degree can be controlled to a desired opening degree is difficult to be secured, in the condition where the refrigerant pressure is high or in the condition where the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant is large, the same functional effects as those obtained by the control of the utilization-side expansion valve 51a of the above embodiment can be more reliably obtained. Note that the same applies to the second utilization-side expansion mechanism 151b and the third utilization-side expansion mechanism 151c.
In the branch units 6a, 6b, and 6c of the above embodiment, the secondary-side unit 4a is provided with, instead of the first control valves 66a, 66b, and 66c, first control valves 96a, 96b, and 96c and first check valves 196a, 196b, and 196c, and provided with, instead of the second control valves 67a, 67b, and 67c, second control valves 97a, 97b, and 97c and second check valves 197a, 197b, and 197c. The secondary-side unit 4a further includes, in the branch units 6a, 6b, and 6c, connection flow paths 98a, 98b, and 98c that connect the first branch pipes 63a, 63b, and 63c to the second branch pipes 64a, 64b, and 64c. The connection flow paths 98a, 98b, and 98c are provided with check valves 99a, 99b, and 99c. Hereinafter, the first control valve 96a, the second control valve 97a, the connection flow path 98a, and the check valve 99a provided in the first branch unit 6a are described. For the corresponding configurations of the second branch unit 6b and the third branch unit 6c, instead of a suffix “a” indicating each part, a suffix “b” or “c” is added and the description of each part is omitted. In the first branch pipe 63a, the first control valve 96a and the first check valve 196a are provided side by side. In the second branch pipe 64a, the second control valve 97a and the second check valve 197a are provided side by side. Each the first control valve 96a and the second control valve 97a is an electromagnetic valve that can be switched between the open state and the close state. The first check valve 196a is a check valve that allows only a flow of the refrigerant flowing from the first connection pipe 8 toward the junction pipe 62a to pass through. The second check valve 197a is a check valve that allows only a flow of refrigerant flowing from the junction pipe 62a toward the second connection pipe 9 to pass through. The connection flow path 98a connects a portion of the first branch pipe 63a closer to the first connection pipe 8 side than to the first control valve 96a and the first check valve 196a to a portion of the second branch pipe 64a closer to the second connection pipe 9 side than to the second control valve 97a and the second check valve 197a. The check valve 99a allows only a flow of the refrigerant flowing from the second branch pipe 64a toward the first branch pipe 63a. In the above configuration, during the cooling operation, the second control valve 97a is controlled to be opened and the first control valve 96a is controlled to be closed. As a result, a part of the refrigerant, having evaporated in the utilization-side heat exchanger 52a and having passed through the second control valve 97a of the second branch pipe 64a, flows through the second connection pipe 9, and the remaining part of the refrigerant passes through the check valve 99a of the connection flow path 98a and flows to the first connection pipe 8. During the heating operation, the first control valve 96a is controlled to be opened and the second control valve 97a is controlled to be closed. As a result, during a first heating operation, the refrigerant having flowed through the first connection pipe 8 joins with the refrigerant having flowed through the second connection pipe 9 and having passed through the check valve 99a of the connection flow path 98a, and the joined refrigerant flows to pass through the first control valve 96a. Note that, during a second heating operation, the refrigerant having flowed through the first connection pipe 8 flows to pass through the first control valve 96a. When the utilization-side heat exchanger 52a functions as an evaporator for the refrigerant during the cooling dominant operation and the heating dominant operation, the first control valve 96a is controlled to be closed and the second control valve 97a is controlled to be opened. As a result, the refrigerant having evaporated in the utilization-side heat exchanger 52a passes through the second control valve 97a of the second branch pipe 64a and flows to the second connection pipe 9. When the utilization-side heat exchanger 52a functions as a radiator for the refrigerant during the cooling dominant operation and the heating dominant operation, the first control valve 96a is controlled to be opened and the second control valve 97a is controlled to be closed. As a result, the refrigerant having flowed through the first connection pipe 8 is allowed to pass through the first control valve 96a of the first branch pipe 63a and is sent to the utilization-side heat exchanger 52a. Note that each of the first control valve 96a and the second control valve 97a is an electromagnetic valve including a needle that moves with respect to a valve seat. Therefore, the same problem as the above problem that the valve becomes difficult to be controlled to be in an intended state can possibly occur. On the other hand, as described above, according to the configuration in which the first control valve 96a and the first check valve 196a, and the second control valve 97a and the second check valve 197a, are provided in parallel to each other, the direction of the flow of the refrigerant passing through the first control valve 96a can be limited to one direction, and the direction of the flow of the refrigerant passing through the second control valve 97a can also be limited to one direction. Therefore, even in the case where an electromagnetic valve that can be controlled to be in a desired close state is difficult to be secured, in the condition where the refrigerant pressure is high or in the condition where the pressure difference between the high-pressure refrigerant and the low-pressure refrigerant is large, the same functional effects as those obtained by the control of the first control valve 66a and the second control valve 67a of the above embodiment can be more reliably obtained. Note that the same applies to a configuration in which the first control valve 96b and the first check valve 196b, and the second control valve 97b and the second check valve 197b are provided in parallel to each other, and a configuration in which the first control valve 96c and the first check valve 196c, and the second control valve 97c and the second check valve 197c, are provided in parallel to each other.
Note that, in the first branch unit 6a, each of the first control valve 96a and the second control valve 97a may be an electrically powered expansion valve whose opening degree can be controlled instead of an electromagnetic valve. Specifically, a configuration may be adopted in which the first control valve 96a being an electrically powered expansion valve and the first check valve 196a, and the second control valve 97a being an electrically powered expansion valve and the second check valve 197a, are provided in parallel to each other. The same applies to the second branch unit 6b and the third branch unit 6c.
As described above, the secondary-side unit 4a can also operate in the same manner as the secondary-side unit 4 of the above embodiment.
Note that providing the heat source-side expansion mechanism 11 instead of the secondary-side expansion valve 36 of the above embodiment, providing the utilization-side expansion mechanisms 151a, 151b, and 151c instead of the utilization-side expansion valves 51a, 51b, and 51c, and providing the connection flow paths 98a, 98b, and 98c and the check valves 99a, 99b, and 99c while providing the first control valves 96a, 96b, and 96c and the first check valves 196a, 196b, and 196c instead of the first control valves 66a, 66b, and 66c and while providing the second control valves 97a, 97b, and 97c and the second check valves 197a, 197b, and 197c instead of the second control valves 67a, 67b, and 67c, are matters independent of each other. Therefore, an embodiment in which these are appropriately combined may be adopted.
Note that, even in the secondary-side unit 4a including both of: the utilization units 3a, 3b, and 3c provided with the utilization-side expansion mechanisms 151a, 151b, and 151c; and the branch units 6a, 6b, and 6c in which the first control valves 96a, 96b, and 96c and the first check valves 196a, 196b, and 196c, and the second control valves 97a, 97b, and 97c and the second check valves 197a, 197b, and 197c, are provided in parallel, the utilization unit in the operation stop state may be included during the various operations, similarly to the above embodiment. In this case, for example, when the utilization units 3a, 3b, and 3c including the utilization-side heat exchangers 52a, 52b, and 52c that function as evaporators for the refrigerant, are brought into the operation stop state, the utilization-side expansion mechanisms 151a, 151b, and 151c included in the utilization units 3a, 3b, and 3c brought into the operation stop state are controlled to be closed. More specifically, the first utilization-side expansion valves 91a, 91b, and 91c included in the utilization units 3a, 3b, and 3c brought into the operation stop state are controlled to be closed. In addition, when the utilization units 3a, 3b, and 3c including the utilization-side heat exchangers 52a, 52b, and 52c that function as radiators for the refrigerant, are brought into the operation stop state, the control is performed by, for example, either a control pattern 1 or a control pattern 2. In the control pattern 1, the first utilization-side expansion valves 91a, 91b, and 91c and the second utilization-side expansion valves 94a, 94b, and 94c of the utilization-side expansion mechanisms 151a, 151b, and 151c included in the utilization units 3a, 3b, and 3c brought into the operation stop state are controlled to be closed, and the first control valves 96a, 96b, and 96c included in the branch units 6a, 6b, and 6c connected corresponding to the utilization units 3a, 3b, and 3c brought into the operation stop state are controlled to be closed. In the control pattern 2, the second utilization-side expansion valves 94a, 94b, and 94c of the utilization-side expansion mechanisms 151a, 151b, and 151c included in the utilization units 3a, 3b, and 3c brought into the operation stop state are controlled to be in a predetermined low opening degree, and the first control valves 96a, 96b, and 96c included in the branch units 6a, 6b, and 6c connected corresponding to the utilization units 3a, 3b, and 3c brought into the operation stop state are controlled to be opened.
In the above embodiment, the cascade heat exchanger 35 shared by the heat source unit 2 and the primary-side unit 5 has been described.
Here, for example, as shown in
In addition to the cascade heat exchanger 35, devices included in the heat source unit 2 is accommodated in the heat source casing 2x. The primary-side casing 5x accommodates, as devices constituting a part of the primary-side refrigerant circuit 5a, the primary-side compressor 71, the primary-side switching mechanism 72, the primary-side heat exchanger 74, the primary-side expansion valve 76, the primary-side fan 75, the outside air temperature sensor 77, the primary-side discharge pressure sensor 78, the primary-side control unit 70, and the like.
The heat source casing 2x accommodating the above-described devices and the primary-side casing 5x accommodating the above-described devices may be both disposed outdoors such as on the rooftop of a building, and may be connected to each other via the refrigerant pipe of the primary-side refrigerant circuit 5a.
Alternatively, the heat source casing 2x accommodating the above-described devices may be disposed in an indoor space such as a machine chamber being a separate space from an air conditioning target space provided indoors, and the primary-side casing 5x accommodating the above-described devices may be disposed outdoors such as on the rooftop of a building, and the two casings may be connected to each other via the refrigerant pipe of the primary-side refrigerant circuit 5a.
Note that the first flow path may be a flow path extending between the discharge side of the first compressor and one end of the cascade heat exchanger. The second flow path may be a flow path extending between the other end of the cascade heat exchanger and the first expansion unit. The third flow path may be a flow path extending between one end of the first heat exchanger and the suction side of the first compressor. The cascade heat exchanger may cause heat exchange between the carbon dioxide refrigerant circulating in the first cycle and the heat medium circulating in the second cycle.
Note that the first cycle may include a switching mechanism that switches the flow of the refrigerant. In the case where the first cycle includes the switching mechanism, the third flow path may be a flow path extending from the switching mechanism to the suction side of the first compressor. Further, in the case where the first cycle includes the switching mechanism, the first flow path may be a flow path extending from the switching mechanism to the one end of the cascade heat exchanger.
In addition, the bypass flow path may connect at least one of the first flow path and the second flow path to the third flow path at all times, or may connect the above flow paths to enable switching between the connected state and the non-connected state using an on-off valve or the like.
Further, the heat medium circulating in the second cycle is not limited as long as the heat medium is the one that is different from the carbon dioxide refrigerant, and may be, for example, R32, brine, water, or the like.
The on-off valve may be the one that can be switched between two states, the open state and the close state, or may be the one in which a valve opening degree is controllable.
In addition, the on-off valve may be in the open state from the time before the heat medium starts flowing into the cascade heat exchanger to the time when the heat medium starts flowing into the cascade heat exchanger in the second cycle.
Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure described in claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-082789 | May 2020 | JP | national |
This application is a Continuation of PCT International Application No. PCT/JP2021/017755, filed on May 10, 2021, which claims priority under 35 U.S.C. 119(a) to Patent Application No. 2020-082789, filed in Japan on May 8, 2020, all of which are hereby expressly incorporated by reference into the present application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2021/017755 | May 2021 | US |
| Child | 17981268 | US |
