Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus (1) comprises: a refrigerant circuit (2) including a compressor (10), a radiator (20), a first expansion valve (31), a second expansion valve (32), and an evaporator (40); and a control device (100). The refrigerant circuit (2) further includes: an injection flow path (50) that connects, to an intermediate pressure part (10a) of the compressor (10), a branch part (53) provided in a flow path between the radiator (20) and the first expansion valve (31); and an internal heat exchanger (51) that is provided between the radiator (20) and the branch part (53) and configured to cool a refrigerant flowing between the radiator (20) and the branch part (53) by using a refrigerant flowing through the injection flow path (50). The control device (100) controls the opening of the first expansion valve (31) on the basis of the outlet temperature of the internal heat exchanger (51) or pressure in the injection flow path (50).

Description

Refrigeration cycle equipment

[0001] The present disclosure relates to a refrigeration cycle device.

[0002] Japanese Patent Laid-Open Publication No. 2009-257756 (Patent Document 1) discloses a refrigeration cycle apparatus in which an injection flow path and an internal heat exchanger are added to a refrigerant circuit configured so that refrigerant circulates through the compressor, radiator, expansion valve, and evaporator in that order when the compressor is operated. The injection flow path connects the compressor to a branching portion provided in a flow path between the radiator and the expansion valve, and supplies refrigerant from the branching portion to the compressor. The internal heat exchanger is provided between the radiator and the branching portion and is configured to further cool the refrigerant flowing between the radiator and the branching portion with refrigerant flowing through the injection flow path.

[0003] JP 2009-257756 A

[0004] In the refrigeration cycle device having the injection flow path and the internal heat exchanger as described above, a refrigerant having a high specific heat ratio (for example, carbon dioxide CO ２ When a refrigerant such as a refrigerant coolant is used, the pressure in the injection flow path tends to increase, which may reduce the heat exchange rate of the internal heat exchanger and reduce the capacity of the refrigeration cycle device.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to appropriately control the heat exchange amount of an internal heat exchanger in a refrigeration cycle device equipped with an injection flow path and an internal heat exchanger.

[0006] A refrigeration cycle apparatus according to the present disclosure includes a refrigerant circuit including a compressor, a radiator, a first expansion valve, a second expansion valve, and an evaporator, and configured to circulate refrigerant in this order by operation of the compressor, and a control device. The refrigerant circuit further includes an injection flow path that connects the compressor to a branching portion provided in a flow path between the radiator and the first expansion valve and supplies refrigerant from the branching portion to the compressor, and an internal heat exchanger provided between the radiator and the branching portion and configured to cool the refrigerant flowing between the radiator and the branching portion with refrigerant flowing through the injection flow path. The control device controls the opening degree of the first expansion valve based on the outlet temperature of the internal heat exchanger or the pressure in the injection flow path.

[0007] According to the present disclosure, in a refrigeration cycle device including an injection flow path and an internal heat exchanger, the heat exchange amount of the internal heat exchanger can be appropriately controlled.

[0008] It is a diagram showing an example of the overall configuration of a refrigeration cycle device. It is a flowchart (part 1) showing an example of a processing procedure of a control device. It is a flowchart (part 2) showing an example of a processing procedure of a control device. It is a flowchart (part 3) showing an example of a processing procedure of a control device.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0010] 1 is a diagram schematically illustrating an example of the overall configuration of a refrigeration cycle apparatus 1 according to this embodiment. The refrigeration cycle apparatus 1 includes a refrigerant circuit 2 through which a refrigerant circulates, and a control device 100.

[0011] The refrigerant circuit 2 includes a compressor 10, a radiator 20, a first expansion valve 31, a second expansion valve 32, an evaporator 40, and flow paths P1 to P5. The refrigerant circuit 2 is configured such that, when the compressor 10 is operated, the refrigerant circulates through the compressor 10, flow path P1, the radiator 20, flow path P2, the first expansion valve 31, flow path P3, the second expansion valve 32, flow path P4, the evaporator 40, and flow path P5 in this order.

[0012] In this embodiment, the refrigerant circulating in the refrigerant circuit 2 is a refrigerant with a high specific heat ratio (for example, carbon dioxide CO ２ Carbon dioxide CO ２ When a refrigerant with such a high specific heat ratio is used, the refrigerant may enter a supercritical state under certain conditions, such as a high outside air temperature. Furthermore, when a refrigerant with a high specific heat ratio is used, the temperature of the gas refrigerant discharged from the compressor 10 (hereinafter also referred to as the "compressor discharge temperature") tends to be high.

[0013] The compressor 10 draws in low-temperature, low-pressure refrigerant from the flow path P5, compresses it, and discharges it as high-temperature, high-pressure gas refrigerant to the flow path P1. The compressor 10 discharges the refrigerant at a flow rate that corresponds to its frequency (rotation speed). The frequency (rotation speed) of the compressor 10 is controlled by the control device 100.

[0014] The radiator 20 is a heat exchanger having a flow path through which the refrigerant flows. In the radiator 20, heat exchange occurs between the refrigerant flowing inside the flow path and the air outside the flow path. The high-temperature, high-pressure gas refrigerant discharged from the compressor 10 is cooled by heat exchange in the radiator 20.

[0015] The first expansion valve 31 and the second expansion valve 32 are both pressure reducing devices that reduce the pressure of high-pressure refrigerant. The first expansion valve 31 and the second expansion valve 32 are arranged in this order in the refrigerant flow path from the radiator 20 to the evaporator 40. That is, the first expansion valve 31 is arranged upstream of the second expansion valve 32 in the refrigerant flow. The first expansion valve 31 reduces the pressure of the refrigerant cooled by the radiator 20, and the second expansion valve 32 further reduces the pressure of the refrigerant reduced by the first expansion valve 31. The first expansion valve 31 and the second expansion valve 32 may be, for example, electronically controlled expansion valves equipped with valve bodies whose opening degrees can be adjusted. The opening degrees of the first expansion valve 31 and the second expansion valve 32 are controlled by the control device 100.

[0016] The evaporator 40 is a heat exchanger having a flow path through which the refrigerant flows. In the evaporator 40, heat exchange occurs between the refrigerant flowing inside the flow path and the air outside the flow path. The refrigerant decompressed by the second expansion valve 32 becomes gas refrigerant through heat exchange in the evaporator 40. The gas refrigerant output from the evaporator 40 to the flow path P5 is drawn into the compressor 10.

[0017] Furthermore, the refrigerant circuit 2 includes an injection flow path 50 , an internal heat exchanger 51 , and an injection expansion valve 52 .

[0018] The injection flow path 50 connects a branching portion 53 provided in the flow path P2 (the flow path between the radiator 20 and the first expansion valve 31) with the intermediate pressure section 10a of the compressor 10, and supplies refrigerant including liquid refrigerant from the branching portion 53 to the intermediate pressure section 10a of the compressor 10. The supply of liquid refrigerant from the injection flow path 50 to the intermediate pressure section 10a of the compressor 10 cools the compressor 10. This prevents the discharge temperature of the compressor 10 from rising excessively even when a refrigerant with a high specific heat ratio is used.

[0019] The internal heat exchanger 51 is provided in a portion of the flow path P2 between the radiator 20 and the branching portion 53, and is configured to cool the refrigerant flowing between the radiator 20 and the branching portion 53 with the refrigerant flowing through the injection flow path 50. With this configuration, the refrigerant cooled by the radiator 20 can be further cooled by the internal heat exchanger 51.

[0020] The injection expansion valve 52 is provided in a portion of the injection flow path 50 between the branching portion 53 and the internal heat exchanger 51. The injection expansion valve 52 adjusts the flow rate of the refrigerant flowing through the injection flow path 50. For example, an electronically controlled expansion valve equipped with a valve element whose opening degree can be adjusted can be used as the injection expansion valve 52. The opening degree of the injection expansion valve 52 is controlled by the control device 100.

[0021] 1, a plurality of sensors are arranged in the refrigerant circuit 2 to detect the refrigerant state (pressure, temperature, etc.) at various locations in the refrigerant circuit 2. These sensors output the detection results to the control device 100.

[0022] The control device 100 includes a CPU (Central Processing Unit) 101, a memory 102, and an input / output port (not shown) for inputting and outputting various signals. The control device 100 controls each device (such as the compressor 10, the first expansion valve 31, the second expansion valve 32, and the injection expansion valve 52) of the refrigeration cycle device 1 based on signals from each sensor and device, and programs stored in the memory 102. Note that the control performed by the control device 100 is not limited to software processing, and can also be processed by dedicated hardware (electronic circuitry).

[0023] In addition, when the refrigeration cycle device 1 is used as an air conditioner, it is assumed that the compressor 10, radiator 20, first expansion valve 31, injection flow path 50, internal heat exchanger 51, and injection expansion valve 52 are located outdoors, and the second expansion valve 32 and evaporator 40 are located indoors.

[0024] In the refrigeration cycle device including the injection flow path 50 and the internal heat exchanger 51 as described above, carbon dioxide CO ２ When a refrigerant with a high specific heat ratio such as the above is used, the pressure in the injection flow path 50 (hereinafter also referred to as "injection pressure") tends to be high, which may result in a decrease in the refrigerant temperature difference in the internal heat exchanger 51 (the difference between the refrigerant temperature flowing through flow path P2 and the refrigerant temperature flowing through injection flow path 50), and there is a concern that the heat exchange amount of the internal heat exchanger 51 may decrease.

[0025] Therefore, the refrigeration cycle device 1 according to this embodiment has a two-stage throttle configuration in which a first expansion valve 31 is further provided in the refrigerant flow path from the branching portion 53 to the second expansion valve 32. In addition, the control device 100 controls the opening degree of the first expansion valve 31 based on the temperature of the refrigerant output from the internal heat exchanger 51 to the flow path P2 (hereinafter also referred to as the "outlet temperature of the internal heat exchanger 51") so that the heat exchange amount of the internal heat exchanger 51 becomes an appropriate value.

[0026] 2 is a flowchart showing an example of a processing procedure performed by the control device 100 when controlling the injection expansion valve 52, the first expansion valve 31, and the second expansion valve 32. The flowchart of FIG. 2 is repeatedly executed every time a predetermined condition is satisfied (for example, at predetermined intervals) while the compressor 10 is in operation.

[0027] The control device 100 controls the aperture of the injection expansion valve 52 based on the discharge temperature of the compressor 10 (step S10). For example, when the discharge temperature of the compressor 10 is higher than a threshold temperature, the control device 100 increases the aperture of the injection expansion valve 52 by a predetermined amount. This increases the amount of liquid refrigerant supplied to the intermediate pressure section 10a of the compressor 10 from the injection flow path 50, thereby preventing the discharge temperature of the compressor 10 from increasing excessively. In this way, the injection expansion valve 52 is used to prevent the compressor discharge temperature from increasing excessively. Note that when the discharge temperature of the compressor 10 is lower than the threshold temperature, the control device 100 decreases the aperture of the injection expansion valve 52 by a predetermined amount. This prevents the amount of refrigerant flowing through the injection flow path 50 from increasing excessively.

[0028] Next, the control device 100 controls the aperture of the second expansion valve 32 based on the superheat degree of the refrigerant output from the evaporator 40 to the flow path P5 (hereinafter also referred to as the "outlet superheat degree SH of the evaporator 40") (step S20). For example, the control device 100 increases or decreases the aperture of the second expansion valve 32 so that the outlet superheat degree SH of the evaporator 40 becomes a target superheat degree. In this manner, the second expansion valve 32 is used to control the outlet superheat degree SH of the evaporator 40. The outlet superheat degree SH of the evaporator 40 can be calculated, for example, from the discharge temperature and pressure of the compressor 10.

[0029] Next, as described above, the control device 100 controls the opening degree of the first expansion valve 31 based on the outlet temperature of the internal heat exchanger 51 so that the heat exchange amount of the internal heat exchanger 51 becomes an appropriate value (step S30).

[0030] For example, the control device 100 determines whether the outlet temperature of the internal heat exchanger 51 is higher than the target outlet temperature.

[0031] When the outlet temperature of the internal heat exchanger 51 is higher than the target outlet temperature, the control device 100 reduces the opening of the first expansion valve 31 by a predetermined amount. This reduces the pressure on the low-pressure side (suction side) of the compressor 10, and accordingly reduces the injection pressure. As a result, the heat exchange amount of the internal heat exchanger 51 is increased, and the outlet temperature of the internal heat exchanger 51 can be reduced toward the target outlet temperature.

[0032] On the other hand, when the outlet temperature of the internal heat exchanger 51 is lower than the target outlet temperature, the control device 100 increases the opening of the first expansion valve 31 by a predetermined amount. This increases the pressure on the low-pressure side of the compressor 10, and accordingly increases the injection pressure. As a result, the heat exchange amount of the internal heat exchanger 51 is reduced, and the outlet temperature of the internal heat exchanger 51 can be increased toward the target outlet temperature.

[0033] In this way, the injection expansion valve 52 is used to control the heat exchange amount of the internal heat exchanger 51 .

[0034] As described above, in the refrigeration cycle device 1 according to this embodiment, the first expansion valve 31 has a two-stage throttle configuration provided in the refrigerant flow path from the branching portion 53 to the second expansion valve 32. The control device 100 controls the opening degree of the first expansion valve 31 based on the outlet temperature of the internal heat exchanger 51 so that the heat exchange amount of the internal heat exchanger 51 becomes an appropriate value. ２ Even when a refrigerant with a high specific heat ratio such as the above is used, the injection pressure can be reduced to ensure a sufficient heat exchange amount in the internal heat exchanger 51. As a result, heat dissipation from the refrigerant by the internal heat exchanger 51 is promoted, and the performance of the refrigeration cycle device 1 can be improved.

[0035] Furthermore, carbon dioxide CO is used as a refrigerant. ２When a refrigerant refrigerant is used, under certain conditions such as high outside air temperature, the pressure of the refrigerant may reach a "supercritical state" where the refrigerant exceeds the critical pressure. Refrigerant in a supercritical state does not liquefy, and therefore cannot obtain latent heat of evaporation. However, in this embodiment, even if the refrigerant is in a supercritical state after passing through the radiator 20, the injection pressure can be reduced by controlling the opening of the first expansion valve 31, thereby ensuring the heat exchange amount of the internal heat exchanger 51 and promoting the heat dissipation of the refrigerant by the internal heat exchanger 51, making it easier to liquefy the refrigerant. As a result, carbon dioxide CO ２ Even when operating under high outdoor air temperature conditions using a supercritical refrigerant such as the above, the latent heat of evaporation of the refrigerant can be obtained, and the performance of the refrigeration cycle device 1 can be improved.

[0036] In the refrigeration cycle apparatus 1 according to this embodiment, it is possible to reduce the injection pressure by controlling the aperture of the second expansion valve 32. However, for example, when the refrigeration cycle apparatus 1 is used as an air conditioner, as described above, it is assumed that the injection flow path 50 is disposed outdoors, while the second expansion valve 32 is disposed indoors. In this case, the refrigerant flow path length between the injection flow path 50 and the second expansion valve 32 is significantly large (e.g., several tens of meters or more). Therefore, even if the aperture of the second expansion valve 32 is controlled, it is assumed that the injection pressure cannot be reduced appropriately. However, in the refrigeration cycle apparatus 1 according to this embodiment, the first expansion valve 31 is disposed closer to the injection flow path 50 than the second expansion valve 32 (e.g., outdoors), and the injection pressure is reduced by controlling the aperture of the first expansion valve 31. This allows the injection pressure to be reduced appropriately.

[0037] Furthermore, if the control device 100 is a control device for an outdoor unit, it is also assumed that the control device 100 cannot control the indoor second expansion valve 32. However, in the refrigeration cycle device 1 according to this embodiment, by arranging the first expansion valve 31 outdoors, the control device 100 for the outdoor unit can control the first expansion valve 31 to reduce the injection pressure.

[0038] [Variant 1] In the above-described embodiment, an example was described in which the opening degree of the first expansion valve 31 is controlled based on the outlet temperature of the internal heat exchanger 51. However, the opening degree of the first expansion valve 31 may also be controlled based on the degree of subcooling of the refrigerant output from the internal heat exchanger 51 to the flow path P2 (hereinafter also referred to as the "outlet subcooling degree SC of the internal heat exchanger 51").

[0039] As described above, when carbon dioxide CO2 is used as the refrigerant in the refrigerant circuit 2, the refrigerant pressure may reach a "supercritical state" in which the refrigerant pressure exceeds the critical pressure. In a normal state where the refrigerant pressure is below the critical pressure, the refrigerant state crosses the saturated liquid line when the refrigerant enthalpy is reduced in the radiator 20, and therefore the so-called degree of subcooling can be defined. On the other hand, when the refrigerant pressure is in a supercritical state, the refrigerant pressure exceeds the critical pressure, and therefore the refrigerant state does not cross the saturated liquid line when the refrigerant enthalpy is reduced in the radiator 20, and therefore the so-called degree of subcooling cannot be defined. Therefore, for ease of explanation, the amount of decrease in the refrigerant temperature in the supercritical state from the reference temperature is also referred to as the degree of subcooling in this specification. That is, in this embodiment, the outlet subcooling degree SC of the internal heat exchanger 51 is defined as the amount of decrease in the outlet temperature of the internal heat exchanger 51 from the saturated temperature in a normal state, and as the amount of decrease in the outlet temperature of the internal heat exchanger 51 from the reference temperature in a supercritical state.

[0040] Fig. 3 is a flowchart showing an example of a processing procedure performed by the control device 100 according to the present modified example 1 when controlling the injection expansion valve 52, the first expansion valve 31, and the second expansion valve 32. The flowchart in Fig. 3 is obtained by changing step S30 in the flowchart in Fig. 2 described above to step S30A. The other steps in Fig. 3 (steps having the same numbers as the steps shown in Fig. 2) have already been described, and therefore detailed description thereof will not be repeated here.

[0041] The control device 100 controls the opening degree of the first expansion valve 31 based on the outlet subcooling degree SC of the internal heat exchanger 51 (step S30A).

[0042] For example, the control device 100 determines whether the outlet subcooling degree SC of the internal heat exchanger 51 is higher than the target subcooling degree.

[0043] When the outlet subcooling degree SC of the internal heat exchanger 51 is higher than the target subcooling degree, the control device 100 reduces the opening degree of the first expansion valve 31 by a predetermined amount. This reduces the pressure on the low-pressure side of the compressor 10, and accordingly reduces the injection pressure. As a result, the heat exchange amount of the internal heat exchanger 51 is increased, and the outlet subcooling degree SC of the internal heat exchanger 51 can be reduced toward the target subcooling degree.

[0044] On the other hand, when the outlet subcooling degree SC of the internal heat exchanger 51 is lower than the target subcooling degree, the control device 100 increases the opening degree of the first expansion valve 31 by a predetermined amount. This increases the pressure on the low-pressure side of the compressor 10, and accordingly increases the injection pressure. As a result, the heat exchange amount of the internal heat exchanger 51 is reduced, and the outlet subcooling degree SC of the internal heat exchanger 51 can be increased toward the target subcooling degree.

[0045] As described above, the opening degree of the first expansion valve 31 may be controlled based on the outlet subcooling degree SC of the internal heat exchanger 51. In this way, the heat exchange amount of the internal heat exchanger 51 can also be appropriately controlled.

[0046] [Modification 2] The opening degree of the first expansion valve 31 may be controlled based on the injection pressure.

[0047] Fig. 4 is a flowchart showing an example of a processing procedure performed by the control device 100 according to the second modification when controlling the injection expansion valve 52, the first expansion valve 31, and the second expansion valve 32. The flowchart in Fig. 4 is obtained by changing step S30 in the flowchart in Fig. 2 described above to step S30B. The other steps in Fig. 4 (steps having the same numbers as the steps shown in Fig. 2) have already been described, and therefore detailed description thereof will not be repeated here.

[0048] The control device 100 controls the opening degree of the first expansion valve 31 based on the injection pressure (step S30B).

[0049] For example, the control device 100 determines whether the injection pressure is higher than the target pressure.

[0050] If the injection pressure is higher than the target pressure, the control device 100 reduces the opening of the first expansion valve 31 by a predetermined amount. This reduces the pressure on the low-pressure side of the compressor 10, and the injection pressure decreases toward the target value. As a result, the heat exchange amount of the internal heat exchanger 51 can be increased.

[0051] On the other hand, when the injection pressure is lower than the target pressure, the control device 100 increases the opening of the first expansion valve 31 by a predetermined amount. This increases the pressure on the low-pressure side of the compressor 10, and accordingly increases the injection pressure toward the target pressure. As a result, the heat exchange amount of the internal heat exchanger 51 can be reduced.

[0052] As described above, the opening degree of the first expansion valve 31 may be controlled based on the injection pressure. In this way, the heat exchange amount of the internal heat exchanger 51 can also be appropriately controlled.

[0053] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0054] REFRIGERATION CYCLE DEVICE, 2 REFRIGERATOR CIRCUIT, 10 COMPRESSOR, 11a INTERMEDIATE PRESSURE SECTION, 20 HEAT RADIATING VALVE, 31 FIRST EXPANSION VALVE, 32 SECOND EXPANSION VALVE, 40 EVAPORATOR, 50 INJECTION FLOW FLOW, 51 INTERNAL HEAT EXCHANGER, 52 INJECTION EXPANSION VALVE, 53 BRANCHING SECTION, 100 CONTROL DEVICE, 101 CPU, 102 MEMORY

Claims

1. A refrigeration cycle device comprising: a refrigerant circuit including a compressor, a radiator, a first expansion valve, a second expansion valve, and an evaporator, and configured to circulate refrigerant in this order by operation of the compressor; and a control device, wherein the refrigerant circuit further includes: an injection flow path that connects the compressor to a branch portion provided in a flow path between the radiator and the first expansion valve, and supplies refrigerant from the branch portion to the compressor; and an internal heat exchanger that is provided between the radiator and the branch portion and configured to cool the refrigerant flowing between the radiator and the branch portion with refrigerant flowing through the injection flow path, and the control device controls the opening degree of the first expansion valve based on the outlet temperature of the internal heat exchanger or the pressure in the injection flow path.

2. The refrigeration cycle apparatus of claim 1, wherein the control device determines whether the outlet temperature of the internal heat exchanger is higher than a target outlet temperature, and reduces the opening of the first expansion valve if the outlet temperature of the internal heat exchanger is higher than the target outlet temperature, and increases the opening of the first expansion valve if the outlet temperature of the internal heat exchanger is lower than the target outlet temperature.

3. The refrigeration cycle apparatus of claim 1, wherein the control device determines whether the outlet subcooling degree of the internal heat exchanger calculated from the outlet temperature of the internal heat exchanger is smaller than a target subcooling degree, and reduces the opening degree of the first expansion valve if the outlet subcooling degree of the internal heat exchanger is smaller than the target subcooling degree, and increases the opening degree of the first expansion valve if the outlet subcooling degree of the internal heat exchanger is greater than the target subcooling degree.

4. The refrigeration cycle apparatus of claim 1, wherein the control device determines whether the pressure in the injection flow path is higher than a target pressure, and reduces the opening of the first expansion valve if the pressure in the injection flow path is higher than the target pressure, and increases the opening of the first expansion valve if the pressure in the injection flow path is lower than the target pressure.

5. The refrigeration cycle device according to claim 1, wherein the control device controls the opening degree of the second expansion valve based on the outlet superheat degree of the evaporator.

6. A refrigeration cycle device as described in claim 1, wherein the refrigerant circuit further includes an injection expansion valve provided in a portion of the injection flow path between the branching portion and the internal heat exchanger, and the control device controls the opening degree of the injection expansion valve based on the discharge temperature of the compressor.

7. A refrigeration cycle device as described in claim 1, wherein the compressor, the radiator, the first expansion valve, the injection passage, and the internal heat exchanger are arranged outdoors, and the second expansion valve and the evaporator are arranged indoors.

8. The refrigeration cycle device according to claim 1, wherein the refrigerant is a refrigerant containing carbon dioxide.

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