Refrigeration cycle device

Abstract

A refrigeration cycle device is provided with: a refrigerant circuit (9) to which a compressor (4), a use-side heat exchanger (6) functioning as a condenser, an expansion valve (7), and a heat-source-side heat exchanger (8) functioning as an evaporator are connected by piping; a discharge superheat degree calculation means (26) that calculates the discharge superheat degree of the refrigerant; a heating unit (11) that heats the compressor; and a control means (25) for controlling the opening degree of the expansion valve, the compressor, and the heating means, the control means heating the compressor by the heating means when the discharge superheat degree is lower than a predetermined discharge superheat degree lower limit value and the opening degree of the expansion valve is equal to or less than a predetermined opening degree.

Description

TECHNICAL FIELD

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

[0002] As a refrigeration cycle device, a hot-water supply device is known which has a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected by piping, and a control unit which controls the opening degree of the expansion valve so that the degree of superheat of refrigerant discharged from the compressor, i.e., the discharge superheat degree, becomes a target discharge superheat degree, and the degree of subcooling of refrigerant flowing out of the condenser becomes a target subcooling degree (for example, Patent Literature 1). In the device of this Patent Literature 1, the control unit controls the opening degree of the expansion valve in such a manner that the enthalpy difference in the condenser is set within a target range, whereby the hot-water supply device can exhibit a required capacity.

[0003] At this time, in order to suppress a decrease in reliability of the compressor caused by liquid compression, it is considered to control the opening degree of the expansion valve so that the discharge superheat degree of refrigerant flowing out of the evaporator when the degree of superheat = 0 and the dryness = 1 is taken as a target value (target discharge superheat degree).

[0004] On the other hand, in a case where the discharge superheat degree of refrigerant is low, the solubility of refrigerant in refrigeration oil increases, and the reliability of the compressor decreases, and therefore, as a specification of the compressor, a lower limit value of the discharge superheat degree at which the reliability of the compressor does not decrease is set.

[0005] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: Japanese Patent Application Publication No. 2018-4128 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION However, sometimes the target discharge superheat degree is lower than the lower limit value under a given operating condition, and in this case, the control unit controls the opening degree of the expansion valve to be smaller so that the target discharge superheat degree becomes equal to or higher than the lower limit value. In particular, under an operating condition in which the circulation amount of refrigerant circulating in the refrigerant circuit is small, the increase in the suction superheat degree of refrigerant sucked into the compressor is slow, and even if the control unit controls the opening degree of the expansion valve to be the smallest, the target discharge superheat degree can not reach the lower limit value.

[0006] Further, in a case where a refrigerant having a small specific heat ratio such as R290 is used, the increase in enthalpy in the compression process becomes smaller compared to a refrigerant having a large specific heat ratio. Therefore, the suction superheat degree required for the discharge superheat degree to exceed the lower limit value is relatively high, and the target discharge superheat degree can be lower than the lower limit value. In a low differential pressure operation in which the difference between the suction pressure and the discharge pressure of the compressor is small, the increase in enthalpy in the compression process further becomes smaller, and therefore, the target discharge superheat degree can be lower than the lower limit value.

[0007] Therefore, the present application has been achieved in order to solve such a problem, and has an object to provide a refrigeration cycle device in which a target discharge superheat degree is not lower than a lower limit value of a compressor specification, and in which a decrease in reliability of the compressor can be suppressed.

[0008] Technical means for solving the problem One embodiment of the present application is a refrigeration cycle device including: a refrigerant circuit connected by a pipe to a compressor, a utilization-side heat exchanger functioning as a condenser, an expansion valve, and a heat-source-side heat exchanger functioning as an evaporator; a discharge superheat degree calculation unit that calculates a discharge superheat degree of a refrigerant; a heating unit that heats the compressor; and a control unit that controls an opening degree of the expansion valve, the compressor, and the heating unit, the control unit controlling the opening degree of the expansion valve so that the discharge superheat degree becomes a predetermined target discharge superheat degree, and heating the compressor with the heating unit when the discharge superheat degree is lower than a predetermined lower limit value of the discharge superheat degree and the opening degree of the expansion valve becomes lower than a given opening degree.

[0009] Effects of the Invention According to the refrigeration cycle device of the present application, a target discharge superheat degree is not lower than a lower limit value of a compressor specification, and a decrease in reliability of the compressor can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a circuit diagram showing a heat pump type heating device as a first embodiment of the heat pump cycle device of the present application.

[0011] Figure 2 is a refrigerant circuit of an outdoor unit of the heat pump type heating device.

[0012] Figure 3 is Figure 2 a Mollier diagram related to the refrigerant circuit of

[0013] Figure 4 is a control flow showing a control method of the heat pump type heating device of the first embodiment.

[0014] Figure 5 is a Mollier diagram of the refrigerant circuit when the compressor is operated at a low differential pressure.

[0015] Figure 6 is a Mollier diagram of the refrigerant circuit when a refrigerant with a low specific heat ratio is used.

[0016] Figure 7 is a circuit diagram showing a heat pump type heating device of a second embodiment.

[0017] Figure 8 is a control flow showing a control method of the heat pump type heating device of the second embodiment. DETAILED DESCRIPTION

[0018] Next, the embodiments relating to the present application will be described with reference to the drawings. The embodiments shown below exemplify devices, methods for embodying the technical idea of the present application, and the technical idea of the present application is not limited to the following content in terms of the material, shape, structure, arrangement, etc. of the constituent members. The technical idea of the present application can be applied to various modifications within the technical scope defined in the claims recited in the scope of the patent request.

[0019] (First Embodiment) Figure 1 is a circuit diagram of a heat pump type heating device 1 which is a first embodiment of the present application as a refrigeration cycle device.

[0020] The heat pump type heating device 1 of the first embodiment has an outdoor unit 2 and an indoor unit 3.

[0021] The outdoor unit 2 is connected in series with a compressor 4, a four-way valve 5, a utilization side heat exchanger 6 which performs heat exchange between water and refrigerant, an expansion valve 7, and an outdoor heat exchanger 8 to form a refrigerant circuit 9. Note that the outdoor heat exchanger 8 corresponds to the heat source side heat exchanger of the present application. Further, the direction of the refrigerant circulation is switched by the four-way valve 5. An outdoor fan 10 which blows outside air to the outdoor heat exchanger 8 is also provided.

[0022] A band heater 11 which heats the casing of the compressor 4 is provided in the compressor 4. Note that the band heater 11 corresponds to the heating unit of the present application.

[0023] In the case where the utilization side heat exchanger 6 functions as a condenser, a condenser outlet refrigerant temperature sensor 15 which detects the temperature of the refrigerant which has passed through the utilization side heat exchanger 6 is provided at the refrigerant outlet of the utilization side heat exchanger 6. In the case where the outdoor heat exchanger 8 functions as an evaporator, an evaporator outlet refrigerant temperature sensor 16 which detects the temperature of the refrigerant which has passed through the outdoor heat exchanger 8 is provided at the refrigerant outlet of the outdoor heat exchanger 8. In the case where the outdoor heat exchanger 8 functions as an evaporator, an evaporator inlet refrigerant temperature sensor 17 which detects the temperature of the refrigerant which flows into the outdoor heat exchanger 8 is provided at the refrigerant inlet of the outdoor heat exchanger 8. In addition, on the discharge side of the compressor 4, a discharge pressure sensor 18 which detects the discharge pressure of the refrigerant, and a discharge temperature sensor 19 which detects the discharge temperature of the refrigerant are provided.

[0024] As the refrigerant which circulates in the refrigerant circuit 9 of the outdoor unit 2, for example, R290 (propane) which has a specific heat ratio of 1.3 or less is used. Note that a refrigerant which has a specific heat ratio exceeding 1.3 (for example, R32) can also be used.

[0025] The indoor unit 3 is configured to receive water that has undergone heat exchange with refrigerant in the utilization-side heat exchanger 6 of the outdoor unit 2. The utilization-side heat exchanger 6, the hot water circulation pump 20, and the indoor heat exchanger 21, which exchanges heat between the water and indoor air, are connected in sequence to form a water circulation path 22. A temperature sensor (not shown) for detecting the outlet temperature of the water is installed at the water outlet of the utilization-side heat exchanger 6. Additionally, the indoor unit 3 is equipped with an indoor fan 23 that blows the air that has undergone heat exchange in the indoor heat exchanger 21 into the room.

[0026] The heat pump heating device 1 of the first embodiment includes a control unit 25, which performs the following controls: drive control of the four-way valve 5 and the hot water circulation pump 20; opening control of the expansion valve 7; drive control of the compressor 4; and power control of the heater 11. Additionally, the condenser outlet temperature of the refrigerant is input to the control unit 25 from the condenser outlet refrigerant temperature sensor 15, and the evaporator outlet temperature is input to the control unit 25 from the evaporator outlet refrigerant temperature sensor 16.

[0027] If the heat pump heating device 1 of the first embodiment starts operating, the control unit 25 drives the hot water circulation pump 20 to circulate water between the utilization side heat exchanger 6 and the indoor heat exchanger 21. The control unit 25 has a built-in microcomputer that stores a program for performing the control specific to this embodiment, which switches the four-way valve 5 when the refrigerant circulation direction is reversed during defrosting operation.

[0028] Next, refer to Figure 2 and Figure 3 The state of the refrigerant in the refrigerant circuit 9 of outdoor unit 2 will be explained. Figure 2 The reference points for refrigerant circuit 9 are as follows: Point A represents the connection between compressor 4 and condenser (corresponding to the utilization-side heat exchanger 6, hereinafter referred to as condenser 6); Point B represents the connection between condenser 6 and expansion valve (corresponding to expansion valve 7, hereinafter referred to as expansion valve 7); Point C represents the connection between expansion valve 7 and evaporator (corresponding to outdoor heat exchanger 8, hereinafter referred to as evaporator 8); and Point D represents the connection between evaporator 8 and compressor 4.

[0029] The state of the refrigerant from point A to point D or between points is as follows: Figure 3As shown in the Morrill diagram, the refrigerant changes according to the following processes (1) to (8). (1) The refrigerant in the compression process (between points D and A) is compressed by the compressor 4, and the pressure (vertical axis) and temperature rise together to become a high-temperature and high-pressure superheated vapor. (2) The refrigerant discharged from the compressor 4 (point A) is a high-pressure gaseous refrigerant in a superheated state. (3) The refrigerant in the cooling process (between points A and B) exchanges heat with the water flowing in the water circulation path 22 in the condenser 6 (heat dissipates to the water), and thus becomes a high-pressure subcooled liquid after passing through the states of superheated vapor, saturated vapor, wet vapor, and saturated liquid under constant pressure. (4) The refrigerant flowing out of the condenser 6 (point B) is a high-pressure liquid refrigerant in a subcooled state. (5) The refrigerant in the expansion process (between points B and C) expands through the expansion valve 7, and the pressure (vertical axis) and temperature drop together to become wet vapor. (6) The refrigerant flowing out of expansion valve 7 (point C) is a low-pressure two-phase refrigerant in a liquid-rich state (high liquid-to-liquid ratio). (7) The refrigerant in the evaporation process (between points C and D) exchanges heat with the surrounding air in evaporator 8 (absorbing heat), thereby keeping the pressure constant, and becomes a low-pressure superheated vapor after passing through various states of wet vapor and saturated vapor. (8) The refrigerant flowing out of evaporator 8 (point D) is a low-pressure gaseous refrigerant in a superheated state.

[0030] Figure 3 The difference between the refrigerant temperature at point A and the saturated gas temperature at point E on the saturated vapor line at the same pressure as point A is the superheat of the refrigerant discharged from compressor 4, also known as the refrigerant discharge superheat. Additionally, Figure 3 The difference between the refrigerant temperature at point B and the saturated liquid temperature at point F on the same pressure as point B is the refrigerant subcooling.

[0031] Figure 3 The refrigerant discharge superheat in the Morrill diagram is set as the target value (target discharge superheat) when the refrigerant flowing out of evaporator 8 (point D) is on the saturated vapor line (absorption superheat = 0 and dryness = 1). The target discharge superheat varies according to the values ​​of condensing temperature (pressure) and evaporating temperature (pressure).

[0032] Here, the specifications for compressor 4 include a lower limit for discharge superheat (discharge superheat lower limit) that does not reduce the reliability of compressor 4. The discharge superheat lower limit for compressor 4 is set, for example, to 10°C.

[0033] like Figure 1 As shown, the control unit 25 of the heat pump heating device 1 has a discharge superheat calculation unit 26 and a target discharge superheat calculation unit 27.

[0034] The discharge superheat calculation unit 26 calculates the current discharge superheat of the refrigerant. The specific calculation method is the difference between the saturation vapor temperature, i.e., the condensing temperature (converted from the discharge pressure of the refrigerant detected by the discharge pressure sensor 18) of the saturated vapor line in the Mollier diagram of the refrigerant shown in FIG. 6, and the discharge temperature of the refrigerant detected by the discharge temperature sensor 19. Figure 3

[0035] In addition, the target discharge superheat calculation unit 27 calculates the target discharge superheat by substituting the condensing temperature of the refrigerant, which is converted from the detection value of the discharge pressure sensor 18, and the evaporating temperature of the refrigerant, which is detected by the evaporator inlet refrigerant temperature sensor 17, into the operation formula stored in advance in the control unit 25. The target discharge superheat is the target value (target discharge superheat) when the refrigerant (point D) flowing out of the evaporator 8 is located on the saturated vapor line (suction superheat = 0 and dryness = 1). These discharge superheat calculation units 26 and target discharge superheat calculation unit 27 are realized by software that causes the control unit 25 to function.

[0036] Next, Figure 4 is a control flow indicating the control of the expansion valve 7 and the energization control of the heater 11 when the heat pump-type heating device 1 is operated. Note that before starting this control method, it is determined that the switch Sc is set to "0".

[0037] First, in step ST1 of Figure 4 the condenser outlet temperature of the refrigerant detected by the condenser outlet refrigerant temperature sensor 15 and the evaporator outlet temperature of the refrigerant detected by the evaporator outlet refrigerant temperature sensor 16 input to the control unit 25 are read in. Next, in step ST2, the discharge superheat calculation unit 26 calculates the current discharge superheat. Next, in step ST3, the target discharge superheat calculation unit 27 calculates the target discharge superheat.

[0038] Next, in step ST4, the control unit 25 subtracts the target discharge superheat from the current discharge superheat, and controls the opening degree of the expansion valve 7 according to the subtraction operation result. That is, when the subtraction result is positive, the control is performed in such a manner that the opening degree of the expansion valve 7 is increased, and when the subtraction result is negative, the control is performed in such a manner that the opening degree of the expansion valve 7 is decreased.

[0039] Next, in step ST5, the control unit 25 determines whether or not the target discharge superheat is lower than the lower limit value of the discharge superheat (for example, 10°C).

[0040] ​In the determination in this step ST5, in the case where the target discharge superheat degree is lower than the lower limit value of the discharge superheat degree (step ST5: YES), the step ST6 is entered, and in the case where the target discharge superheat degree is equal to or higher than the lower limit value of the discharge superheat degree (step ST5: NO), the step ST9 is entered.

[0041] In the step ST6 entered in the case where the determination in the step ST5 is YES, the control unit 25 determines whether the opening degree of the expansion valve 7 is the minimum opening degree. It should be noted that the opening degree of the expansion valve 7 being the minimum opening degree corresponds to the opening degree of the expansion valve being the given opening degree in the present application. In the determination in this step ST6, in the case where the opening degree of the expansion valve 7 is the minimum opening degree (step ST6: YES), the step ST7 is entered, and in the case where the opening degree of the expansion valve 7 is not the minimum opening degree (step ST6: NO), the step ST1 is returned to.

[0042] In the step ST7 entered in the case where the opening degree of the expansion valve 7 is the minimum opening degree, the energization control of the heater 11 is performed. At this time, the target value of the discharge superheat degree is changed from the target discharge superheat degree calculated in the step ST3 to the heating-time target discharge superheat degree (> the lower limit value of the discharge superheat degree), and the heater-equipped output is adjusted so that the discharge superheat degree becomes the heating-time target discharge superheat degree. Next, in the step ST8, the determination switch Sc is set to "1" after which the step ST1 is returned to.

[0043] On the other hand, in the step ST9 entered in the case where the determination in the step ST5 is NO, it is determined whether the current discharge superheat degree is equal to or higher than the target discharge superheat degree. In the determination in this step ST9, in the case where the current discharge superheat degree is equal to or higher than the target discharge superheat degree (step ST9: YES), the step ST10 is entered, and in the case where the current discharge superheat degree is lower than the target discharge superheat degree (step ST9: NO), the step ST1 is returned to.

[0044] In the step ST10, it is determined whether the determination switch Sc is "1" or not. In the determination in this step ST10, in the case where the determination switch Sc is "1" (step ST10: YES), the step ST11 is entered, and in the case where the determination switch Sc is not "1" (step ST10: NO), the step ST1 is returned to.

[0045] In the step ST11, the determination switch Sc is set to "0". Next, in the step ST12, the control unit 25 stops the energization control of the heater 11. Thereafter, the control of the present embodiment is ended. Figure 4

[0046] Here, it is possible that the target discharge superheat degree does not reach the lower limit value of the discharge superheat degree (for example, 10°C) of the compressor 4 specifications when the heat pump-type heating device 1 is operated.

[0047] That is,​Figure 5 A Mollier diagram of the heat pump-type heating device 1 during low differential pressure operation of the compressor 4 is shown. During heating operation of the heat pump-type heating device 1 at low load operation and high outside air temperature, the circulation amount of the refrigerant circulating in the refrigerant circuit 9 is small, and the differential pressure between the suction pressure and the discharge pressure of the compressor 4 is small, that is, the low differential pressure operation. During such low differential pressure operation, even if the refrigerant sucked into the compressor 4 is in a state where the suction superheat degree is 0 and the dryness is 1 (suction is on the saturated vapor line), the discharge superheat degree is a relatively small value. Therefore, even if the control unit 25 controls the opening degree of the expansion valve 7 to be the minimum, the target discharge superheat degree becomes a relatively small value (for example, 8°C), and it is possible that the discharge superheat degree lower limit value is not reached.

[0048] In addition, in the control shown in Figure 5 , a Mollier diagram of the heat pump-type heating device 1 when using R32 refrigerant, which has a relatively high specific heat ratio, as the refrigerant is shown, Figure 6 a Mollier diagram of the heat pump-type heating device 1 when using R290 (propane), which has a relatively low specific heat ratio, as the refrigerant, as in the present embodiment, is shown. In the case of using R290, the increase in enthalpy during compression is small compared to refrigerants with a large specific heat ratio. Therefore, the suction superheat degree required for the discharge superheat degree to exceed the lower limit value is relatively high, and the target discharge superheat degree is lower than the lower limit value. Therefore, even if the control unit 25 controls the opening degree of the expansion valve 7 to be the minimum, the target discharge superheat degree is a relatively small value (for example, 8°C), and it is possible that the discharge superheat degree lower limit value is not reached.

[0049] In contrast, in the control shown in Figure 4 , in a case where the target discharge superheat degree does not reach the discharge superheat degree lower limit value (step ST5: Yes), and the opening degree of the expansion valve 7 is the minimum opening degree (step ST6: Yes), the housing of the compressor 4 is heated by performing energization control of the heater 11 (step ST7). By heating the housing of the compressor 4 with the heater 11, the target discharge superheat degree is raised to be above the discharge superheat degree lower limit value, and it is possible to suppress a decrease in reliability of the compressor 4.

[0050] Here, if the discharge superheat degree lower limit value is controlled as the target value, in a case where the discharge superheat degree is lower than the discharge superheat degree lower limit value due to load variation, the current discharge superheat degree cannot be controlled by adjusting the opening degree of the expansion valve 7 alone. Therefore, in the present embodiment, a heating-time target discharge superheat degree, which is a high target discharge superheat degree that anticipates a change in discharge superheat degree due to load variation, is set, the target discharge superheat degree is compared with the discharge superheat degree lower limit value, and control is performed, whereby it is possible to perform fine control of the discharge superheat degree by the expansion valve 7.

[0051] In addition, by heating the casing of the compressor 4 with heater 11, the temperature of the refrigeration oil rises, and the solubility of the refrigerant in the refrigeration oil decreases, thus further suppressing the decrease in the reliability of the compressor 4.

[0052] Furthermore, the heat exchanger 6 on the utilization side of the heat pump heating device 1 is a water-refrigerant heat exchanger that facilitates heat exchange between water and refrigerant. During hot water supply operation at high external gas temperatures, it easily transforms into low differential pressure operation of the compressor 4. Figure 4 The control shown raises the target discharge superheat to above the lower limit of discharge superheat, thereby suppressing the decrease in the reliability of compressor 4.

[0053] Furthermore, even when using R290 (propane) with a low specific heat ratio, by conducting Figure 4 The control shown allows the target discharge superheat to rise above the lower limit of discharge superheat, which can also suppress the decrease in the reliability of compressor 4.

[0054] (Second Implementation) then, Figure 7 This is a circuit diagram of a heat pump heating device 1, which is a second embodiment of the refrigeration cycle device of the present invention. Figure 7 The structure of the loop diagram shown is similar to Figure 1 The difference in the circuit diagram of the heat pump heating device 1 shown in the first embodiment is that, in addition to the discharge superheat calculation unit 26 and the target discharge superheat calculation unit 27, the control unit 25 also has a supercooling calculation unit 32 and a target supercooling extraction unit 33.

[0055] in addition, Figure 8 This describes the control flow of the expansion valve 7 and the power supply control of the heater 11 during operation of the heat pump heating device 1 in the second embodiment. Figure 8 Control process and Figure 4 The difference in the supercooling control process shown is that, instead of Figure 4 The expansion valve opening process based on the degree of subcooling shown in step ST4 is performed in step ST20.

[0056] The following explains the expansion valve opening process based on subcooling in step ST20.

[0057] First, the subcooling calculation unit 32 calculates the current subcooling degree. Specifically, the calculation method involves calculating the subcooling degree based on the refrigerant discharge pressure detected by the discharge pressure sensor 30. Figure 3The saturation liquid temperature (condensation temperature) of the saturation liquid line in the Mollier diagram of the refrigerant shown. Then, the supercooling degree calculation unit 32 calculates the current supercooling degree by subtracting the temperature of the refrigerant that has passed through the utilization-side heat exchanger 6 detected by the condenser outlet refrigerant temperature sensor 15 from this saturation liquid temperature.

[0058] The target supercooling degree extraction unit 33 stores a target supercooling degree table. The target supercooling degree table is set with target supercooling degrees corresponding to the condensing pressure state and the rotational speed (unit: rps) of the compressor 4. The target supercooling degree extraction unit 33 determines the condensing pressure state of the pressure value (condensing pressure) detected by the discharge pressure sensor 30, and extracts the target supercooling degree from the target supercooling degree table based on the current rotational speed of the compressor 4.

[0059] Then, the control unit 25 subtracts the target supercooling degree extracted by the target supercooling degree extraction unit 33 from the current supercooling degree calculated by the supercooling degree calculation unit 32. Also, when the result of subtracting the target supercooling degree from the current supercooling degree is positive, the control unit 25 controls in such a manner that the opening degree of the expansion valve 7 is increased, and when the result of subtracting the target supercooling degree from the current supercooling degree is negative, the control unit 25 controls in such a manner that the opening degree of the expansion valve 7 is decreased.

[0060] Also in the second embodiment, as in the first embodiment, by raising the target discharge superheat degree to the discharge superheat degree lower limit value or more, it is possible to suppress a decrease in the reliability of the compressor 4.

[0061] Also, in the supercooling degree-based expansion valve opening degree processing of step ST20, Figure 8 In the supercooling degree-based expansion valve opening degree processing of step ST20, the target supercooling degree is extracted from the target supercooling degree table that takes into account the condensing pressure and the rotational speed of the compressor 4, the target supercooling degree is subtracted from the current supercooling degree, and the opening degree control of the expansion valve 7 is performed in accordance with the subtraction result, so it is possible to perform delicate discharge superheat degree control by the expansion valve 7.

[0062] In addition, in the utilization-side heat exchanger 6 (condenser), the enthalpy difference is secured, so it is possible to perform operation of a high-efficiency heat pump cycle with improved COP (Coefficient Of Performance ~ performance coefficient).

[0063] REFERENCE NUMERALS 1 Heat pump-type heating device 2 Outdoor unit 3 Indoor unit 4 Compressor 5 Four-way valve 6 Utilization-side heat exchanger 7 Expansion valve 8 Outdoor heat exchanger 9 refrigerant circuit 10 outdoor fan 11 with heater 15 condenser outlet refrigerant temperature sensor 16 evaporator outlet refrigerant temperature sensor 17 evaporator inlet refrigerant temperature sensor 18 discharge pressure sensor 19 discharge temperature sensor 20 hot water circulating pump 21 indoor heat exchanger 22 water circulating path 23 indoor fan 25 control unit 26 discharge superheat degree calculation unit 27 target discharge superheat degree calculation unit 30 discharge pressure sensor 31 discharge temperature sensor 32 subcooling degree calculation unit 33 target subcooling degree extraction unit.

Claims

1. A refrigeration cycle device, characterized in that, The refrigeration cycle device includes: The refrigerant circuit is connected via piping to a compressor, a heat exchanger on the condenser side, an expansion valve, and a heat source side heat exchanger on the evaporator side. The discharge superheat calculation unit calculates the discharge superheat of the refrigerant; A heating unit that heats the compressor; as well as The control unit controls the opening degree of the expansion valve, the compressor, and the heating unit. The control unit heats the compressor using the heating unit when the discharge superheat is lower than a predetermined lower limit of discharge superheat and the opening degree of the expansion valve is below a given opening degree.

2. The refrigeration cycle device according to claim 1, characterized in that, The control unit continues to heat the compressor by the heating unit until the discharge superheat reaches or exceeds the lower limit of the discharge superheat.

3. The refrigeration cycle device according to claim 1 or 2, characterized in that, The heat exchanger used on the side is a water-refrigerant heat exchanger that allows water to exchange heat with the refrigerant.

4. The refrigeration cycle device according to claim 1 or 2, characterized in that, The control unit controls the opening degree of the expansion valve so that the discharge superheat is a predetermined target discharge superheat.

5. The refrigeration cycle device according to claim 1 or 2, characterized in that, The refrigeration cycle device includes a subcooling calculation unit for calculating the subcooling degree of the refrigerant. The control unit controls the opening degree of the expansion valve so that the subcooling degree becomes a predetermined target subcooling degree.

6. The refrigeration cycle device according to claim 1 or 2, characterized in that, The given opening degree is the minimum opening degree of the expansion valve.

7. The refrigeration cycle device according to claim 1 or 2, characterized in that, The heating unit is a heater that heats the housing of the compressor.

8. The refrigeration cycle device according to claim 1 or 2, characterized in that, The specific heat ratio of the refrigerant is 1.3 or less.

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