Refrigeration cycle device

Abstract

A refrigeration cycle device (1) is provided with: a first refrigerant circuit (C1) that is provided with a compressor (11), a first heat exchanger (12), an expansion device (13), and a third heat exchanger (30), and that is configured so as to circulate a first refrigerant; a second refrigerant circuit (C2) that is provided with a pump (21), a flow rate adjustment valve (24), a second heat exchanger (22), and the third heat exchanger (30), and that is configured so as to circulate a second refrigerant that is a non-azeotropic refrigerant mixture; and a control device (100) that controls the flow rate adjustment valve (24) to adjust the amount of the second refrigerant flowing into the second heat exchanger (22) so that the dryness of the second refrigerant flowing out from the second heat exchanger (22) becomes 1 or less.

Description

Refrigeration Cycle Equipment

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

[0002] As disclosed in Japanese Patent Laid-Open No. 2014-16078, a refrigeration cycle device configured to improve the coefficient of performance (COP) by improving electric heating performance is known. The refrigeration cycle device disclosed in Japanese Patent Laid-Open No. 2014-16078 is configured to ensure a required flow rate without increasing the flow velocity of the refrigerant in the evaporator by setting the quality fraction of the refrigerant flowing out of the evaporator to less than 1, thereby preventing an increase in pressure loss in the evaporator.

[0003] JP 2014-16078 A

[0004] According to the refrigeration cycle device disclosed in JP 2014-16078 A, it is possible to prevent an increase in pressure loss in the evaporator. However, if the wet refrigerant having a quality fraction of less than 1 flowing out of the evaporator is sucked into the compressor, liquid compression will occur in the compressor, and the refrigeration cycle may not function properly.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a refrigeration cycle device that improves COP by improving electric thermal performance while allowing the refrigeration cycle to function well.

[0006] The refrigeration cycle device according to the present disclosure comprises: a first refrigerant circuit including a compressor, a first heat exchanger, an expansion device, and a third heat exchanger, and configured to circulate a first refrigerant; a second refrigerant circuit including a pump, a flow control valve, a second heat exchanger, a third heat exchanger, and a receiver, and configured to circulate a second refrigerant that is a non-azeotropic refrigerant mixture; and a control device that controls the flow control valve to adjust the amount of the second refrigerant flowing into the second heat exchanger so that the quality fraction of the second refrigerant flowing out of the second heat exchanger is 1 or less.

[0007] According to the refrigeration cycle apparatus of the present disclosure, the compressor is included in a first refrigerant circuit in which a first refrigerant circulates, while the second heat exchanger is included in a second refrigerant circuit in which a second refrigerant circulates, so that the second refrigerant will not be drawn into the compressor even if the quality fraction of the second refrigerant flowing out of the second heat exchanger is controlled to be equal to or less than 1. As a result, the refrigeration cycle apparatus can prevent an increase in pressure loss in the second heat exchanger by controlling the quality fraction of the refrigerant flowing out of the second heat exchanger to be equal to or less than 1, while maintaining good refrigeration cycle function, thereby improving COP through improved electric heating performance.

[0008] 1 is a diagram illustrating a configuration of a refrigeration cycle device according to an embodiment; and FIG. 2 is a flowchart illustrating processing executed by a control device of a refrigeration cycle device according to an embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. While multiple embodiments will be described below, it is anticipated from the beginning that the configurations described in each embodiment will be appropriately combined. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0010] The configuration of a refrigeration cycle apparatus 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the refrigeration cycle apparatus 1 according to an embodiment. The refrigeration cycle apparatus 1 is a cascade refrigeration cycle apparatus that cools an object to be cooled using a first refrigerant and a second refrigerant, and can be applied to refrigeration apparatuses that have a relatively low evaporation temperature and are used for refrigeration or freezing.

[0011] 1, the refrigeration cycle apparatus 1 includes an outdoor unit 10 installed outside a room that is not the target of cooling, an indoor unit 20 installed in a space to be cooled, extension pipes 4, 5, and a control device 100. The outdoor unit 10 and the indoor unit 20 are connected by the extension pipes 4, 5. The space to be cooled is, for example, an indoor space or a showcase in which the target of cooling is placed.

[0012] The refrigeration cycle apparatus 1 includes a first refrigerant circuit C1 and a second refrigerant circuit C2. In the example of Fig. 1, the first refrigerant circuit C1 is included in the outdoor unit 10. A portion of the second refrigerant circuit C2 is included in the outdoor unit 10, and another portion of the second refrigerant circuit C2 is included in the indoor unit 20. A first refrigerant is sealed in the first refrigerant circuit C1, and the first refrigerant circulates within the first refrigerant circuit C1. A second refrigerant is sealed in the second refrigerant circuit C2, and the second refrigerant circulates within the second refrigerant circuit C2.

[0013] The second refrigerant has a lower boiling point than the first refrigerant at the same pressure. That is, in the refrigeration cycle apparatus 1, the first refrigerant circuit C1 is a high-temperature side refrigerant circuit, and the second refrigerant circuit C2 is a low-temperature side refrigerant circuit.

[0014] The first refrigerant is preferably a natural refrigerant that provides a high COP for the first refrigerant circuit C1 and a relatively low Global Warming Potential (GWP). For example, the first refrigerant may be a single refrigerant made of propane or a mixed refrigerant containing propane and another refrigerant.

[0015] The second refrigerant circulating in the second refrigerant circuit C2 on the low-temperature side passes through the extension pipes 4, 5, and therefore can be directly released into the space to be cooled if the second refrigerant leaks from the extension pipes 4, 5. For this reason, the second refrigerant is preferably a natural refrigerant that is non-flammable, undergoes a relatively small temperature drop due to pressure loss, and has a relatively small GWP.

[0016] Furthermore, the second refrigerant is a non-azeotropic refrigerant mixture, which is a mixture of multiple types of refrigerants with different boiling points, such as a high-boiling point refrigerant and a low-boiling point refrigerant. For example, the second refrigerant is a non-azeotropic refrigerant mixture containing carbon dioxide and another refrigerant with a boiling point different from that of carbon dioxide. More specifically, the second refrigerant is a non-azeotropic refrigerant mixture containing carbon dioxide (R744) and propane (R290). Note that the second refrigerant is not limited to carbon dioxide (R744) and propane (R290), and may be another non-azeotropic refrigerant mixture, such as R463A containing carbon dioxide (R744).

[0017] A non-azeotropic refrigerant mixture generates a temperature gradient, which is the difference between the saturated gas temperature and the saturated liquid temperature, during a phase change. For example, in the case of a non-azeotropic refrigerant mixture consisting of carbon dioxide and propane, the temperature gradient obtained by subtracting the saturated liquid temperature from the saturated gas temperature is 5 K or more. The greater the difference in boiling point between the multiple refrigerants contained in the non-azeotropic refrigerant mixture, the greater the temperature gradient. On the other hand, in the case of a single refrigerant, the saturation temperature is constant, so no saturation gradient occurs. In the refrigeration cycle device 1, a non-azeotropic refrigerant mixture is used as the second refrigerant, which generates a temperature gradient in the second refrigerant. Therefore, there is a one-to-one correspondence between the temperature of the non-azeotropic refrigerant mixture during a phase change under a certain pressure and the dryness fraction of the non-azeotropic refrigerant mixture.

[0018] The first refrigerant circuit C1 includes a compressor 11, a first heat exchanger 12, an expansion device 13, a third heat exchanger 30, and pipes 51 to 54. The first refrigerant circuit C1 is configured such that, when the compressor 11 is operated, the first refrigerant circulates through the compressor 11, the first heat exchanger 12, the expansion device 13, and the third heat exchanger 30 in this order.

[0019] The compressor 11 is configured to operate and stop, and to change its rotational speed during operation, under the control of the control device 100. The control device 100 controls the compressor 11 to arbitrarily change the drive frequency of the compressor 11. The compressor 11 changes the number of rotations per unit time, i.e., the rotational speed, in response to changes in the drive frequency, thereby changing the amount of refrigerant discharged. Various types of compressors can be used for the compressor 11, including scroll, rotary, and screw types. The suction side of the compressor 11 is connected to the third heat exchanger 30 via piping 54. The discharge side of the compressor 11 is connected to the first heat exchanger 12 via piping 51.

[0020] The first heat exchanger 12 functions as a condenser in the first refrigerant circuit C1, and exchanges heat between the first refrigerant and air surrounding the first heat exchanger 12 (e.g., outside air). One end of the first heat exchanger 12 is connected to the discharge side of the compressor 11 via a pipe 51. The other end of the first heat exchanger 12 is connected to the expansion device 13 via a pipe 52.

[0021] The expansion device 13 is, for example, an electronic expansion valve whose opening is adjusted under the control of the control device 100. The expansion device 13 reduces the pressure of the first refrigerant that has flowed in and allows the first refrigerant obtained by the pressure reduction to flow out. The control device 100 can adjust the amount of pressure reduction of the first refrigerant and the amount of first refrigerant flowing through the expansion device 13 by controlling the expansion device 13. The expansion device 13 may be a capillary tube. One end of the expansion device 13 is connected to the first heat exchanger 12 via a pipe 52. The other end of the expansion device 13 is connected to the third heat exchanger 30 via a pipe 53.

[0022] The second refrigerant circuit C2 includes a pump 21, a flow control valve 24, a second heat exchanger 22, a third heat exchanger 30, a receiver 23, pipes 61 to 67, and extension pipes 4 and 5. The second refrigerant circuit C2 is configured such that, by operation of the pump 21, the second refrigerant circulates through the pump 21, the flow control valve 24, the second heat exchanger 22, the third heat exchanger 30, and the receiver 23 in that order.

[0023] The pump 21, under the control of the control device 100, draws in the second refrigerant in a liquid state stored in the receiver 23 and discharges it to the flow rate control valve 24. The suction side of the pump 21 is connected to the receiver 23 via a pipe 67. The discharge side of the pump 21 is connected to the flow rate control valve 24 via a pipe 61.

[0024] The flow rate control valve 24 is, for example, an electronic expansion valve whose opening is adjusted under the control of the control device 100. The flow rate control valve 24 adjusts the amount of second refrigerant that has flowed in and causes the second refrigerant to flow out to the second heat exchanger 22. The control device 100 can adjust the amount of second refrigerant flowing through the flow rate control valve 24 by controlling the flow rate control valve 24. For example, the control device 100 can reduce the amount of second refrigerant flowing through the flow rate control valve 24 by reducing the opening of the flow rate control valve 24, and can increase the amount of second refrigerant flowing through the flow rate control valve 24 by increasing the opening of the flow rate control valve 24. One end of the flow rate control valve 24 is connected to the discharge side of the pump 21 via a pipe 61. The other end of the flow rate control valve 24 is connected to the second heat exchanger 22 via a pipe 62.

[0025] The second heat exchanger 22 functions as an evaporator in the second refrigerant circuit C2, and exchanges heat between the second refrigerant and a heat medium such as air surrounding the second heat exchanger 22. One end of the second heat exchanger 22 is connected to the flow control valve 24 via a pipe 62. The other end of the second heat exchanger 22 is connected to the third heat exchanger 30 via pipes 63 and 64 and an extension pipe 5.

[0026] The third heat exchanger 30 is, for example, a cascade condenser that functions as an evaporator in the first refrigerant circuit C1 and as a condenser in the second refrigerant circuit C2. The third heat exchanger 30 includes a first passage H1 through which a first refrigerant flows and a second passage H2 through which a second refrigerant flows. The third heat exchanger 30 exchanges heat between the first refrigerant flowing through the first passage H1 and the second refrigerant flowing through the second passage H2. In the third heat exchanger 30, the second refrigerant dissipates heat to the first refrigerant, causing the first refrigerant to evaporate and the second refrigerant to condense. The third heat exchanger 30 may be a plate heat exchanger, a double-pipe heat exchanger, or a dry shell-and-tube heat exchanger. One end of the first passage H1 of the third heat exchanger 30 is connected to the expansion device 13 via a pipe 53. The other end of the first passage H1 in the third heat exchanger 30 is connected to the suction port of the compressor 11 via a pipe 54. One end of the second passage H2 in the third heat exchanger 30 is connected to the second heat exchanger 22 via pipes 63 and 64 and the extension pipe 5. The other end of the second passage H2 in the third heat exchanger 30 is connected to the receiver 23 via pipes 65 and 66 and the extension pipe 4.

[0027] The receiver 23 temporarily stores the second refrigerant that flows in from the third heat exchanger 30 via pipes 65, 66 and the extension pipe 4. One end of the receiver 23 is connected to the third heat exchanger 30 via pipes 65, 66 and the extension pipe 4. The other end of the receiver 23 is connected to the suction side of the pump 21 via pipe 67. The second refrigerant circuit C2 does not necessarily have to include the receiver 23.

[0028] The control device 100 includes a calculation unit 101 and a storage unit 102. The control device 100 is capable of communicating with each actuator, such as the compressor 11, the pump 21, and the flow rate control valve 24, in order to control each actuator. The control device 100 may be mounted on either the outdoor unit 10 or the indoor unit, or may be separate from the outdoor unit 10 and the indoor unit 20 (for example, a cloud server device).

[0029] The arithmetic unit 101 is a computing entity (computer) that executes predetermined processing. The arithmetic unit 101 is configured with a processor such as a central processing unit (CPU), a microprocessing unit (MPU), a tensor processing unit (TPU), or a graphics processing unit (GPU). A processor, which is an example of the arithmetic unit 101, has the function of executing predetermined processing by executing a predetermined program. However, some or all of these functions may be implemented using dedicated hardware circuits such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). The term "processor" is not limited to processors in the narrow sense that execute processing using a stored program, such as a CPU, MPU, TPU, or GPU, but may also include hardwired circuits such as an ASIC or FPGA. Furthermore, the arithmetic unit 101 is not limited to von Neumann computers such as a CPU or GPU, but may also be configured with non-von Neumann computers such as a quantum computer or an optical computer. The arithmetic unit 101 described above may also be interpreted as a processing circuit that executes predetermined processing. The computing unit 101 may be configured as a single chip or multiple chips. Furthermore, the processor and related processing circuits may be configured as multiple computers interconnected by wire or wirelessly via a local area network or a wireless network. The processor and related processing circuits may be configured as a cloud computer that performs remote computations based on input data and outputs the computation results to another device in a remote location.

[0030] The memory unit 102 provides a storage area for storing program code, work memory, etc. when the calculation unit 101 executes a predetermined process. The memory unit 102 may be one or more non-transitory computer-readable media. Examples of the memory unit 102 include volatile memories such as dynamic random access memory (DRAM) and static random access memory (SRAM), and non-volatile memories such as read-only memory (ROM) and flash memory. The memory unit 102 may also be one or more computer-readable storage media. Examples of the memory unit 102 include storage devices such as hard disk drives (HDDs) and solid-state drives (SSDs).

[0031] The storage unit 102 stores a control program 120 executed by the calculation unit 101. The calculation unit 101 executes the control program 120 stored in the storage unit 102 to control the actuators of the first refrigerant circuit C1 and the second refrigerant circuit C2.

[0032] In the refrigeration cycle apparatus 1 configured as described above, the first refrigerant circulates through the first refrigerant circuit C1 as follows. Specifically, in the first refrigerant circuit C1, the compressor 11 draws in the low-temperature, low-pressure gaseous first refrigerant that has flowed in from the third heat exchanger 30 and compresses the drawn first refrigerant to increase the pressure of the first refrigerant. The compressor 11 discharges the compressed high-temperature, high-pressure gaseous first refrigerant to the first heat exchanger 12.

[0033] The first heat exchanger 12 functions as a condenser, exchanging heat between the high-temperature, high-pressure gaseous first refrigerant from the compressor 11 and the air drawn in from the outside. The gaseous first refrigerant that has released heat into the air through this heat exchange condenses inside the first heat exchanger 12 and changes into a high-temperature, high-pressure liquid first refrigerant. The high-temperature, high-pressure liquid first refrigerant obtained by the first heat exchanger 12 flows out to the expansion device 13.

[0034] The expansion device 13 reduces the pressure of the first refrigerant in a high-temperature, high-pressure liquid state from the first heat exchanger 12. The first refrigerant in a low-temperature, low-pressure, gas-liquid two-phase state obtained by the expansion device 13 flows into the third heat exchanger 30.

[0035] In the first refrigerant circuit C1, the third heat exchanger 30 functions as an evaporator, exchanging heat between the first refrigerant in a low-temperature, low-pressure, two-phase gas-liquid state from the expansion device 13 and the second refrigerant flowing through the second refrigerant circuit C2. The first refrigerant in a two-phase gas-liquid state absorbs heat from the second refrigerant through this heat exchange and evaporates inside the third heat exchanger 30, changing into the first refrigerant in a low-temperature, low-pressure gas state. The low-temperature, low-pressure first refrigerant obtained by the third heat exchanger 30 flows into the compressor 11.

[0036] In the refrigeration cycle apparatus 1, the second refrigerant circulates through the second refrigerant circuit C2 as follows: Specifically, in the second refrigerant circuit C2, the pump 21 draws in the second refrigerant in a low-temperature, low-pressure liquid state stored in the receiver 23 and discharges it to the flow control valve 24.

[0037] The flow rate adjustment valve 24 adjusts the amount of the second refrigerant that has flowed in under the control of the control device 100 , and causes the second refrigerant to flow out to the second heat exchanger 22 .

[0038] The second heat exchanger 22 functions as an evaporator, exchanging heat between the second refrigerant from the flow rate adjustment valve 24 and air drawn in from the space to be cooled. The second refrigerant absorbs heat from the air through this heat exchange and flows out to the third heat exchanger 30. The air whose heat has been absorbed by the second refrigerant in the second heat exchanger 22 is sent back into the space to be cooled. This cools the space to be cooled.

[0039] In the second refrigerant circuit C2, the third heat exchanger 30 functions as a condenser, exchanging heat between the second refrigerant from the second heat exchanger 22 and the first refrigerant flowing through the first refrigerant circuit C1. The second refrigerant, which has released heat to the first refrigerant through this heat exchange, is condensed inside the third heat exchanger 30 and changes into the second refrigerant in a low-temperature, low-pressure liquid state. The low-temperature, low-pressure second refrigerant obtained by the third heat exchanger 30 flows into the receiver 23.

[0040] Here, the refrigeration cycle apparatus 1 further includes a temperature sensor 40 that measures the temperature (saturation temperature) of the second refrigerant flowing out from the second heat exchanger 22. Specifically, the temperature sensor 40 is provided in a pipe 63 connected to the outflow side of the second heat exchanger 22. The temperature sensor 40 measures the temperature T of the second refrigerant flowing out from the second heat exchanger 22, and transmits a signal indicating the measured temperature T to the control device 100.

[0041] Based on a signal received from temperature sensor 40, control device 100 acquires temperature T of the second refrigerant flowing out of second heat exchanger 22 measured by temperature sensor 40 and stores the temperature T in memory unit 102. Based on temperature T acquired from temperature sensor 40, control device 100 controls the aperture of flow control valve 24 to adjust the amount of second refrigerant flowing into second heat exchanger 22 so that the dryness fraction of the second refrigerant flowing out of second heat exchanger 22 is 1 or less. For example, based on temperature T acquired from temperature sensor 40, control device 100 controls the aperture of flow control valve 24 to adjust the amount of second refrigerant flowing into second heat exchanger 22 so that the dryness fraction of the second refrigerant flowing out of second heat exchanger 22 is 0.8 to 1.0.

[0042] Control of the flow rate control valve 24 by the control device 100 will be described with reference to Fig. 2. Fig. 2 is a flowchart for explaining processing executed by the control device 100 of the refrigeration cycle apparatus 1 according to the embodiment. The control device 100 periodically (for example, once every 30 seconds) executes the processing of the flowchart shown in Fig. 2 by, for example, the calculation unit 101 executing a control program 120 stored in the storage unit 102. Note that in the figure, "S" is used as an abbreviation for "STEP."

[0043] As shown in FIG. 2, the control device 100 acquires the temperature T of the second refrigerant flowing out from the second heat exchanger 22, which functions as an evaporator, from a temperature sensor 40 provided at the outlet of the second heat exchanger 22 (S1).

[0044] The control device 100 determines whether the temperature T is within a predetermined range (S2). The predetermined range is the temperature range of the second refrigerant when the dryness fraction of the second refrigerant flowing out of the second heat exchanger 22 is 0.8 to 1.0. The second refrigerant is a non-azeotropic refrigerant mixture, and therefore a temperature gradient occurs during a phase change, resulting in a one-to-one correspondence between the dryness fraction and the temperature. Therefore, if the temperature range of the second refrigerant when the dryness fraction of the second refrigerant is 0.8 to 1.0 is stored in advance in the memory unit 102, the control device 100 can determine whether the temperature T is within the temperature range corresponding to a dryness fraction of 0.8 to 1.0 in the determination process of S2.

[0045] If the temperature T is within the temperature range corresponding to a dryness fraction of 0.8 to 1.0 (YES in S2), the control device 100 ends the processing of this flowchart. On the other hand, if the temperature T is not within the temperature range corresponding to a dryness fraction of 0.8 to 1.0 (NO in S2), the control device 100 controls the aperture of the flow rate adjustment valve 24 so that the dryness fraction of the second refrigerant flowing out of the second heat exchanger 22 is 0.8 to 1.0 (S3), and ends the processing of this flowchart.

[0046] For example, when the quality fraction of the second refrigerant flowing out of the second heat exchanger 22 exceeds 1.0, the control device 100 increases the opening of the flow control valve 24. As a result, the heat exchange amount in the second heat exchanger 22 does not change, but the amount of the second refrigerant flowing into the second heat exchanger 22 increases, and the temperature T of the second refrigerant flowing out of the second heat exchanger 22 decreases (i.e., the quality fraction of the second refrigerant decreases to 1.0 or less).

[0047] On the other hand, when the quality fraction of the second refrigerant flowing out of the second heat exchanger 22 is less than 0.8, the control device 100 reduces the opening of the flow control valve 24. As a result, the heat exchange amount in the second heat exchanger 22 does not change, but the amount of the second refrigerant flowing into the second heat exchanger 22 decreases, and the temperature T of the second refrigerant flowing out of the second heat exchanger 22 increases (i.e., the quality fraction of the second refrigerant increases to 0.8 or more).

[0048] The second refrigerant flowing out of the second heat exchanger 22 is in a gas state inside the second heat exchanger 22 when the quality fraction is 1, and is in a gas-liquid two-phase state (wet refrigerant) inside the second heat exchanger 22 when the quality fraction is less than 1. Therefore, when the quality fraction of the second refrigerant flowing out of the second heat exchanger 22 is 1 or less (for example, within a range of 0.8 to 1.0), the second refrigerant flowing through the second heat exchanger 22 is in a gas state or in a gas-liquid two-phase state (wet refrigerant) just before becoming a gas, thereby increasing the density of the second refrigerant flowing through the second heat exchanger 22. In order to improve the COP of the refrigeration cycle, it is necessary to ensure the required flow rate of the second refrigerant flowing through the second heat exchanger 22. In the refrigeration cycle apparatus 1, the quality fraction of the second refrigerant flowing out of the second heat exchanger 22 is 1 or less, thereby increasing the density of the second refrigerant flowing through the second heat exchanger 22. Therefore, the refrigeration cycle apparatus 1 can ensure the required flow rate of the second refrigerant flowing through the second heat exchanger 22. As a result, the refrigeration cycle apparatus 1 can improve the COP by improving the electric thermal performance, thereby achieving energy saving effects.

[0049] Furthermore, the refrigeration cycle apparatus 1 includes a compressor 11 in a first refrigerant circuit C1 on the high-temperature side, which includes a first heat exchanger 12 functioning as a condenser, and a second refrigerant circuit C2 in which a second heat exchanger 22 functioning as an evaporator, which includes a second refrigerant that is a non-azeotropic refrigerant mixture flowing out of the second heat exchanger 22 as a wet refrigerant, thereby improving the COP. As a result, the wet refrigerant flowing out of the second heat exchanger 22 is not drawn into the compressor 11, and liquid compression is not performed in the compressor 11, allowing the refrigeration cycle to function well. As a result, the refrigeration cycle apparatus 1 can improve the COP by improving the electric heating performance while maintaining the refrigeration cycle functioning well.

[0050] Furthermore, the refrigeration cycle device 1 reduces the environmental impact because the second refrigerant, which is a non-azeotropic refrigerant mixture, contains carbon dioxide, which has a relatively small GWP. Furthermore, by using a natural refrigerant composed of carbon dioxide and propane as the second refrigerant, the refrigeration cycle device 1 can lower the triple point (freezing point) of carbon dioxide and can handle ultra-low temperature freezing at -60°C or below.

[0051] [Summary] The refrigeration cycle device 1 according to the present disclosure comprises a first refrigerant circuit C1 including a compressor 11, a first heat exchanger 12, an expansion device 13, and a third heat exchanger 30, and configured to circulate a first refrigerant; a second refrigerant circuit C2 including a pump 21, a flow control valve 24, a second heat exchanger 22, and the third heat exchanger 30, and configured to circulate a second refrigerant that is a non-azeotropic refrigerant mixture; and a control device 100 that controls the flow control valve 24 to adjust the amount of the second refrigerant flowing into the second heat exchanger 22 so that the dryness fraction of the second refrigerant flowing out of the second heat exchanger 22 is 1 or less.

[0052] According to the above configuration, the compressor 11 is included in the first refrigerant circuit C1 in which the first refrigerant circulates, while the second heat exchanger 22 is included in the second refrigerant circuit C2 in which the second refrigerant circulates, so even if the quality fraction of the second refrigerant flowing out of the second heat exchanger 22 is controlled to be equal to or less than 1, the second refrigerant will not be drawn into the compressor 11. As a result, the refrigeration cycle apparatus 1 can prevent an increase in pressure loss in the second heat exchanger 22 by controlling the quality fraction of the refrigerant flowing out of the second heat exchanger 22 to be equal to or less than 1, while still allowing the refrigeration cycle to function well, thereby improving the COP through improved electric heating performance.

[0053] The control device 100 controls the flow rate adjustment valve 24 so that the quality fraction of the second refrigerant flowing out of the second heat exchanger 22 is 0.8 to 1.0.

[0054] According to the above configuration, the refrigeration cycle apparatus 1 can convert the second refrigerant flowing out of the second heat exchanger 22 into an appropriate wet refrigerant that contributes to improving the electric heating performance.

[0055] The refrigeration cycle apparatus 1 further includes a temperature sensor 40 that measures the temperature of the second refrigerant flowing out of the second heat exchanger 22. The control device 100 controls the flow rate adjustment valve 24 based on the measurement value of the temperature sensor 40.

[0056] According to the above configuration, the refrigeration cycle device 1 can adjust the amount of second refrigerant flowing into the second heat exchanger 22 by controlling the opening degree of the flow control valve 24 based on the temperature T of the second refrigerant flowing out of the second heat exchanger 22.

[0057] The second refrigerant contains carbon dioxide. According to the above configuration, the refrigeration cycle device 1 can improve the COP by improving the electric heating performance while reducing the environmental load.

[0058] The second refrigerant includes propane. According to the above configuration, the refrigeration cycle device 1 can lower the triple point (freezing point) of carbon dioxide and can also handle ultra-low temperature freezing of −60° C. or lower.

[0059] 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 by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0060] 1 Refrigeration cycle device, 4, 5 Extension piping, 10 Outdoor unit, 11 Compressor, 12 First heat exchanger, 13 Expansion device, 20 Indoor unit, 21 Pump, 22 Second heat exchanger, 23 Receiver, 24 Flow control valve, 30 Third heat exchanger, 40 Temperature sensor, 51, 52, 53, 54, 61, 62, 63, 64, 65, 66, 67 Piping, 100 Control device, 101 Calculation unit, 102 Memory unit, 120 Control program, C1 First refrigerant circuit, C2 Second refrigerant circuit, H1 First passage, H2 Second passage.

Claims

1. A refrigeration cycle device comprising: a first refrigerant circuit including a compressor, a first heat exchanger, an expansion device, and a third heat exchanger, and configured to circulate a first refrigerant; a second refrigerant circuit including a pump, a flow control valve, a second heat exchanger, and the third heat exchanger, and configured to circulate a second refrigerant, which is a non-azeotropic refrigerant mixture; and a control device that controls the flow control valve to adjust the amount of the second refrigerant flowing into the second heat exchanger so that the dryness fraction of the second refrigerant flowing out of the second heat exchanger is 1 or less.

2. A refrigeration cycle device as described in claim 1, wherein the control device controls the flow rate regulating valve so that the dryness of the second refrigerant flowing out of the second heat exchanger is 0.8 to 1.

0.

3. A refrigeration cycle device as described in claim 1 or claim 2, further comprising a temperature sensor for measuring the temperature of the second refrigerant flowing out of the second heat exchanger, and the control device controls the flow control valve based on the measurement value of the temperature sensor.

4. A refrigeration cycle device according to any one of claims 1 to 3, wherein the second refrigerant includes carbon dioxide.

5. A refrigeration cycle device according to any one of claims 1 to 4, wherein the second refrigerant includes propane.

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