Refrigeration cycle device

Abstract

The present invention comprises: a refrigerant circuit that has a compressor, a condenser, an evaporator, and a pressure reduction device, and that circulates a refrigerant; a radiator that, in the refrigerant circuit, is disposed between the compressor and the condenser, and that performs heat exchange between the refrigerant and a heat medium; an adjustment valve that, in the refrigerant circuit, is disposed between the radiator and condenser and that enables adjustment of a degree of opening; and a control device that controls the degree of opening of the adjustment valve on the basis of the result of comparing a first target condensation temperature and a first condensation temperature of the refrigerant in the radiator.

Description

Refrigeration cycle equipment

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

[0002] In a conventional refrigeration cycle system including a refrigerant circuit connected to a compressor, a condenser, a pressure reducing device, and an evaporator, a technology has been proposed in which high-temperature gas refrigerant, i.e., hot gas, discharged from the compressor is supplied to the evaporator to utilize the heat of the hot gas. For example, Patent Document 1 proposes a vehicle air conditioning system including a hot water heater that uses engine coolant as a heat source and a refrigeration cycle circuit that is normally used to cool the vehicle interior. In Patent Document 1, when the heating capacity of the hot water heater is insufficient, hot gas is supplied to the evaporator, which functions as a cooler to cool the vehicle interior during cooling, and air heated by the evaporator is supplied to the vehicle interior.

[0003] Japanese Patent Application Publication No. 11-180138

[0004] Generally, compressors are installed outside the vehicle or the room, but when the outside temperature is low, for example in winter, the outside air reduces the temperature and pressure of the hot gas discharged from the compressor, reducing the amount of heat that can be utilized from the hot gas.In addition to utilizing the heat of hot gas as an auxiliary for a hot water heater for a vehicle as described in Patent Document 1, there is also a demand for utilizing the heat of hot gas for air conditioning in buildings, etc., and therefore a technology that can maintain the amount of heat that can be extracted from hot gas regardless of the outside temperature has been desired.

[0005] The present disclosure has been made in light of the above-mentioned problems, and aims to provide a refrigeration cycle device that can maintain the amount of heat that can be extracted from hot gas regardless of the ambient temperature of the compressor.

[0006] The refrigeration cycle device according to the present disclosure includes a refrigerant circuit having a compressor, a condenser, an evaporator, and a pressure reducing device for circulating a refrigerant; a radiator disposed in the refrigerant circuit between the compressor and the condenser for heat exchange between the refrigerant and a heat medium; a regulating valve disposed in the refrigerant circuit between the radiator and the condenser and capable of adjusting its opening; and a control device for controlling the opening of the regulating valve based on a comparison result between a first condensing temperature of the refrigerant in the radiator and a first target condensing temperature.

[0007] In the refrigeration cycle device according to the present disclosure, a control valve is provided between the radiator and the condenser, and the aperture of the control valve is controlled based on a comparison result between the first condensing temperature in the radiator and the first target condensing temperature. Therefore, even if the first condensing temperature fluctuates due to, for example, the influence of the outside air temperature, the aperture of the control valve can be controlled to maintain the amount of heat extracted from the hot gas in the radiator.

[0008] Fig. 1 is a diagram showing a configuration example of a refrigeration cycle device according to embodiment 1. Fig. 2 is a ph diagram of the refrigeration cycle device according to embodiment 1. Fig. 3 is a flowchart explaining control of an adjustment valve in the refrigeration cycle device according to embodiment 1. Fig. 4 is a diagram showing a configuration example of a refrigeration cycle device according to embodiment 2. Fig. 5 is a diagram showing a configuration example of a refrigeration cycle device according to embodiment 3.

[0009] Hereinafter, embodiments of a refrigeration cycle device according to the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals denote the same or equivalent parts, and this applies throughout the specification. Furthermore, the configurations of the components shown in the entire specification are merely examples and are not limited to these descriptions. Furthermore, the size relationships between the components in the following drawings may differ from those in reality.

[0010] Embodiment 1. Fig. 1 is a diagram showing an example of the configuration of a refrigeration cycle apparatus 100 according to Embodiment 1. The refrigeration cycle apparatus 100 includes a compressor 1, a condenser 2, a pressure reducing device 3, and an evaporator 4, which are connected by piping to form a refrigerant circuit 7 for circulating a refrigerant. The refrigeration cycle apparatus 100 of this embodiment includes a radiator 5 between the compressor 1 and the condenser 2 of the refrigerant circuit 7, and a control valve 6 between the radiator 5 and the condenser 2. The refrigeration cycle apparatus 100 also includes a condenser fan 8 for blowing air to the condenser 2, a control device 15, a first pressure sensor 11, a first temperature sensor 12, a second pressure sensor 13, and a second temperature sensor 14. The refrigerant circulating through the refrigerant circuit 7 is not particularly limited, and may be, for example, a natural refrigerant such as carbon dioxide, hydrocarbon, or helium; a chlorine-free refrigerant such as HFC-410A or HFC-407C; or a fluorocarbon refrigerant such as R-22 or R-134a.

[0011] The compressor 1 draws in and compresses low-pressure gas refrigerant, and discharges it as high-pressure gas refrigerant. A reciprocating, rotary, scroll, or screw compressor, for example, is used as the compressor 1. The operating frequency of the compressor 1 is controlled by a control device 15.

[0012] The condenser 2 exchanges heat between the refrigerant flowing through the refrigerant circuit 7 and air. In the condenser 2, the high-temperature refrigerant radiates heat to the air and condenses. The condenser 2 is, for example, a fin-tube heat exchanger, and exchanges heat between the refrigerant flowing inside the circular or flat tubes and air supplied by a condenser fan 8, thereby condensing the refrigerant.

[0013] The pressure reducing device 3 reduces the pressure of the refrigerant flowing out from the condenser 2 and causes it to expand. The pressure reducing device 3 is, for example, an electronic adjustment valve whose opening degree is variable. The opening degree of the pressure reducing device 3 is controlled by the control device 15.

[0014] The evaporator 4 exchanges heat between the refrigerant flowing through the refrigerant circuit 7 and a fluid. In the evaporator 4, the refrigerant, which has been decompressed and expanded by the pressure reducing device 3, absorbs heat from the fluid and evaporates. The fluid that exchanges heat with the refrigerant in the evaporator 4 may be, for example, air in a freezer or refrigerator, or a liquid such as water or brine. When the refrigerant is to be heat exchanged with air, the evaporator 4 is, for example, a fin-tube heat exchanger, and exchanges heat between the refrigerant flowing inside circular or flat tubes and air supplied by a fan (not shown). When the refrigerant is to be heat exchanged with a liquid, the evaporator 4 exchanges heat between the refrigerant and a liquid supplied by a pump (not shown) or the like.

[0015] The condenser fan 8 supplies air to the condenser 2. The condenser fan 8 is, for example, a propeller fan, a turbo fan, a sirocco fan, or a crossflow fan driven by a motor. The rotation speed of the condenser fan 8 is controlled by the control device 15.

[0016] The radiator 5 is disposed between the compressor 1 and the condenser 2, and performs heat exchange between the refrigerant discharged from the compressor 1 and a heat medium that is a heat exchange target. The heat medium in this embodiment is a liquid such as water or brine that flows through the heat medium circuit 20. The radiator 5 in this embodiment has a refrigerant flow path 5a through which the refrigerant flows, and a heat medium flow path 5b through which the heat medium flows. The refrigerant flow path 5a is connected to piping that constitutes the refrigerant circuit 7.

[0017] The regulating valve 6 is provided in the piping between the radiator 5 and the condenser 2 and adjusts the cross-sectional area of ​​the flow path through which the refrigerant passes. The regulating valve 6 is an electronic expansion valve (linear expansion valve) with a multi-stage variable aperture. It is preferable to select a regulating valve 6 with a valve diameter that does not cause pressure loss when fully open. When the regulating valve 6 is fully open, the regulating valve 6 allows the refrigerant to pass through it in the same way as the piping. When the aperture of the regulating valve 6 is narrowed and the flow path becomes narrow, refrigerant accumulates upstream of the regulating valve 6. The aperture of the regulating valve 6 is controlled by pulses output from the control device 15. The control device 15 outputs one or more pulses to the regulating valve 6 and controls the aperture of the regulating valve 6 in the open or closed direction depending on the number of consecutive pulses. The greater the number of consecutive pulses, the greater the change in the aperture of the regulating valve 6.

[0018] The first pressure sensor 11 is disposed downstream of the compressor 1 and upstream of the radiator 5 and measures the pressure of the refrigerant discharged from the compressor 1. The first temperature sensor 12 is disposed downstream of the compressor 1 and upstream of the radiator 5 and measures the temperature of the refrigerant discharged from the compressor 1. The second pressure sensor 13 is disposed downstream of the regulating valve 6 and upstream of the condenser 2 and measures the pressure of the refrigerant flowing into the condenser 2. The second temperature sensor 14 is disposed downstream of the regulating valve 6 and upstream of the condenser 2 and measures the temperature of the refrigerant flowing into the condenser 2. The first temperature sensor 12 and the second temperature sensor 14 are, for example, thermistors. Information measured by the first pressure sensor 11, the first temperature sensor 12, the second pressure sensor 13, and the second temperature sensor 14 is input to the control device 15.

[0019] The control device 15 converts the refrigerant pressure measured by the first pressure sensor 11 to obtain the condensing temperature of the refrigerant in the radiator 5. The control device 15 also converts the refrigerant pressure measured by the second pressure sensor 13 to obtain the condensing temperature of the refrigerant in the condenser 2. In the following description, the condensing temperature in the radiator 5 will be referred to as the first condensing temperature, and the condensing temperature in the condenser 2 will be referred to as the second condensing temperature. The control device 15 also controls the operations of the compressor 1, the pressure reducing device 3, the adjustment valve 6, and the condenser fan 8 based on the first condensing temperature, the second condensing temperature, the temperature measured by the first temperature sensor 12, and the temperature measured by the second temperature sensor 14.

[0020] The control device 15 is composed of a computer having a memory for storing data and programs necessary for control and a processor such as a CPU (Central Processing Unit) for executing the programs, a dedicated processing circuit such as an ASIC (Application Specific IC) or FPGA (Field Programmable Gate Array), or both.

[0021] Next, the heat medium circuit 20 through which the heat medium flows for heat exchange with the refrigerant in the refrigerant circuit 7 will be described. The heat medium circuit 20 includes a heat medium flow path 5b of the radiator 5, a pump 21, and a load-side heat exchanger 22, which are connected by piping to circulate the heat medium. The heat medium flowing through the heat medium flow path 5b of the radiator 5 exchanges heat with the refrigerant flowing through the refrigerant flow path 5a. The pump 21 is a device for circulating water through the heat medium circuit 20, and is, for example, an inverter pump or a constant-speed pump with a variable rotation speed. The load-side heat exchanger 22 exchanges heat between the heat medium flowing through the heat medium circuit 20 and a heat exchange target. The heat exchange target with the heat medium may be either air or liquid, but in this embodiment, it is air blown by a load-side fan 23. The load-side heat exchanger 22 is, for example, an air-conditioning heat exchanger for indoor air conditioning, installed indoors, and exchanges heat between the heat medium and the indoor air blown by the load-side fan 23.

[0022] The operations of the pump 21 and the load-side fan 23 are controlled by a control device 24. The control device 24 is composed of a computer including a memory for storing data and programs required for control and a processor such as a CPU for executing the programs, a dedicated processing circuit such as an ASIC or FPGA, or both.

[0023] 1 is an example, and is not limited to the illustrated embodiment. For example, the heat medium circuit 20 may be provided with a plurality of load-side heat exchangers 22. The heat medium flowing through the heat medium flow path 5b may flow parallel to or counter to the refrigerant flowing through the refrigerant flow path 5a.

[0024] FIG. 2 is a ph diagram of the refrigeration cycle apparatus 100 according to the first embodiment. Referring to FIG. 2, the state change of the refrigerant will be described. The high-temperature, high-pressure refrigerant discharged from the compressor 1 flows into the radiator 5, where it dissipates heat to a heat medium to be exchanged. The refrigerant flowing out of the radiator 5 is depressurized by the regulating valve 6. Note that when the regulating valve 6 is fully open, the regulating valve 6 does not depressurize. The refrigerant flowing out of the regulating valve 6 flows into the condenser 2, where it exchanges heat with the air and condenses. The refrigerant flowing out of the condenser 2 is depressurized by the depressurizing device 3, becoming a low-temperature, low-pressure two-phase refrigerant. The refrigerant depressurized by the depressurizing device 3 flows into the evaporator 4, where it exchanges heat with the air in, for example, a refrigerator or freezer, and evaporates and gasifies. The gasified refrigerant in the evaporator 4 returns to the compressor 1.

[0025] In this manner, the air in, for example, a refrigerator compartment or a freezer compartment where the evaporator 4 is installed is cooled. The refrigeration cycle apparatus 100 of this embodiment is provided with a radiator 5 upstream of the condenser 2. Heat that would be rejected by the condenser 2 if the radiator 5 were not present is utilized in the radiator 5 to heat the heat medium in the heat medium circuit 20. As shown in FIG. 1 , in the radiator 5, the refrigerant flowing through the refrigerant flow path 5a radiates heat to the heat medium flowing through the heat medium flow path 5b, thereby heating the heat medium. The heat medium heated by the radiator 5 circulates through the heat medium circuit 20 and exchanges heat with air blown by the load-side fan 23 in the load-side heat exchanger 22. The high-temperature heat medium flowing through the load-side heat exchanger 22 radiates heat to the air, thereby heating the room in which the load-side heat exchanger 22 is installed. In this way, the refrigerant circuit 7 and the heat medium circuit 20 work together to form a refrigeration cycle system that cools the room in which the evaporator 4 is installed and at the same time heats the room in which the load side heat exchanger 22 is installed.

[0026] When the outside air temperature is low, such as in winter, the temperature and pressure of the high-temperature gas refrigerant (hereinafter referred to as hot gas) discharged from the compressor 1 are reduced by the low-temperature outside air. This reduces the amount of heat available from the hot gas in the radiator 5, and it may not be possible to obtain enough heat to heat the heat medium to a temperature required for heating in the load-side heat exchanger 22.

[0027] Therefore, the refrigeration cycle device 100 of this embodiment is provided with an adjustment valve 6 between the radiator 5 and the condenser 2, and by controlling the opening degree of this adjustment valve 6, the amount of heat that can be extracted from the hot gas by the radiator 5 is controlled regardless of the ambient temperature of the condenser 2.

[0028] Specifically, the control device 15 controls the aperture of the regulating valve 6 based on a comparison between the first condensing temperature of the refrigerant in the radiator 5 and a first target condensing temperature, which is a target value for the first condensing temperature. When the first condensing temperature is lower than the first target condensing temperature, the control device 15 reduces the aperture of the regulating valve 6 to throttle the refrigerant flow path. When the regulating valve 6 is fully open, the regulating valve 6 simply allows the refrigerant to pass through, just like a pipe. However, when the aperture of the regulating valve 6 is reduced, the refrigerant accumulates upstream of the regulating valve 6. This suppresses a decrease in the amount of heat supplied from the hot gas to the heat medium in the radiator 5, which is located upstream of the regulating valve 6.

[0029] Furthermore, the control device 15 controls the target rotation speed of the condenser fan 8 that blows air to the condenser 2 based on a comparison between the second condensing temperature of the refrigerant in the condenser 2 and a second target condensing temperature, which is a target value for the second condensing temperature. The target rotation speed is controlled to be higher as the second condensing temperature is higher than the second target condensing temperature, and the higher rotation speed of the condenser fan 8 brings the second condensing temperature closer to the second target condensing temperature. When the second condensing temperature becomes lower than the second target condensing temperature, the target rotation speed of the condenser fan 8 becomes 0 rpm and the condenser fan 8 stops.

[0030] Fig. 3 is a flowchart illustrating the control of the regulating valve 6 in the refrigeration cycle apparatus 100 according to Embodiment 1. The control shown in Fig. 3 is executed by the control device 15 during operation of the refrigeration cycle apparatus 100. The initial opening of the regulating valve 6 is fully open.

[0031] First, it is determined whether the time elapsed since the start of the compressor 1 is less than a threshold time (step S1). This threshold time is, for example, about 10 minutes. The regulating valve 6 is maintained in a fully open state until the threshold time has elapsed since the start of the compressor 1. This prevents the opening degree of the regulating valve 6 from being changed unnecessarily due to transient operation after the start of the compressor 1. If the time elapsed since the start of the compressor 1 is less than the threshold time (step S1: YES), the process returns to the start.

[0032] When the elapsed time since the start of the compressor 1 is equal to or greater than the threshold time (step S1: NO), it is determined whether the target rotation speed of the condenser fan 8 is greater than zero (step S2). If the target rotation speed of the condenser fan 8 is greater than zero (step S2: YES), the process returns to the start. Here, as described above, the target rotation speed of the condenser fan 8 is controlled by comparing the second condensing temperature with the second target condensing temperature. If the target rotation speed of the condenser fan 8 is greater than zero, this means that the second condensing temperature is greater than the second target condensing temperature, and therefore the first condensing temperature is also greater than the first target condensing temperature. This means that the heat quantity of the hot gas in the radiator 5 is sufficient.

[0033] If the target rotation speed of the condenser fan 8 is not greater than zero (step S2: NO), that is, if the target rotation speed of the condenser fan 8 is zero, the process proceeds to step S3.

[0034] In steps S3 to S7, the magnitude relationship between the first condensing temperature and the first target condensing temperature and the magnitude of the difference between them are determined. Based on the determination results, a first control is executed in steps S8 to S13, controlling the aperture of the regulating valve 6. Specifically, if the first condensing temperature is equal to or greater than the first target condensing temperature + 2 degrees (step S3: YES), the aperture of the regulating valve 6 is increased by two pulses (step S8). If the first condensing temperature is less than the first target condensing temperature + 2 degrees (step S3: NO) and the first condensing temperature is equal to or greater than the first target condensing temperature + 1 degree (step S4: YES), the aperture of the regulating valve 6 is increased by one pulse (step S9). If the first condensing temperature is less than the first target condensing temperature + 1 degree (step S4: NO) and the first condensing temperature is equal to or greater than the first target condensing temperature (step S5: YES), the aperture of the regulating valve 6 is maintained (step S10).

[0035] If the first condensing temperature is less than the first target condensing temperature (step S5: NO) but is equal to or greater than the first target condensing temperature minus 1 degree (step S6: YES), the aperture of the regulating valve 6 is decreased by one pulse (step S11). If the first condensing temperature is less than the first target condensing temperature minus 1 degree (step S6: NO) but is equal to or greater than the first target condensing temperature minus 2 degrees (step S7: YES), the aperture of the regulating valve 6 is decreased by two pulses (step S12). If the first condensing temperature is less than the first target condensing temperature minus 2 degrees (step S7: NO), the aperture of the regulating valve 6 is decreased by three pulses (step S13).

[0036] As described above, in the processing of steps S3 to S13, when the first condensing temperature is higher than the first target condensing temperature, the aperture of regulating valve 6 is increased to widen the refrigerant flow path. Furthermore, when the first condensing temperature is lower than the first target condensing temperature, the aperture of regulating valve 6 is decreased to narrow the refrigerant flow path. The greater the difference between the first condensing temperature and the first target temperature, the greater the change in the aperture of regulating valve 6. In this way, when the difference between the first condensing temperature and the first target temperature is large, the first condensing temperature can be brought closer to the first target condensing temperature more quickly.

[0037] Note that, instead of increasing the amount of change in the aperture of the regulating valve 6 as the difference between the first condensing temperature and the first target temperature increases, the amount of change in the aperture of the regulating valve 6 may be kept constant. Specifically, when the first condensing temperature is higher than the first target condensing temperature, the aperture of the regulating valve 6 is increased by a fixed pulse, and when the first condensing temperature is lower than the first target condensing temperature, the aperture of the regulating valve 6 is decreased by the fixed pulse. When the first condensing temperature is equal to the first target condensing temperature, the aperture of the regulating valve 6 is maintained. The fixed pulse is a predetermined value, such as two pulses. In this way, the control process of the regulating valve 6 can be more easily achieved.

[0038] As described above, the refrigeration cycle apparatus 100 of this embodiment is provided with the radiator 5 between the compressor 1 and the condenser 2, and the regulating valve 6, the aperture of which is adjustable, between the radiator 5 and the condenser 2. The aperture of the regulating valve 6 is controlled based on a comparison result between the first condensing temperature of the refrigerant in the radiator 5 and the first target condensing temperature. By controlling the aperture of the regulating valve 6, the amount of refrigerant upstream of the regulating valve 6 changes, thereby making it possible to control the discharge temperature and discharge pressure of the compressor 1. Therefore, for example, even when the ambient temperature of the condenser 2 is low, the discharge temperature and discharge pressure of the compressor 1 can be controlled, and the amount of heat obtained from the hot gas in the radiator 5 can be maintained.

[0039] Specifically, when the first condensing temperature is lower than the first target condensing temperature, the control device 15 reduces the aperture of the regulating valve 6. As a result, refrigerant accumulates upstream of the regulating valve 6, the discharge temperature and discharge pressure of the compressor 1 increase, and the compressor input (power consumption of the compressor 1) also increases. The smaller the aperture of the regulating valve 6, the greater the increase in the discharge temperature and discharge pressure of the compressor 1. As the discharge temperature and discharge pressure of the compressor 1 increase, the temperature of the hot gas supplied from the compressor 1 to the radiator 5 increases, making it possible to ensure the amount of heat supplied to the heat medium in the radiator 5.

[0040] Furthermore, when the first condensing temperature is higher than the first target condensing temperature, the control device 15 increases the opening degree of the regulating valve 6, and finally fully opens the regulating valve 6. For example, when there is no shortage of heat quantity in the radiator 5 due to an increase in the outside air temperature, etc., when the regulating valve 6 is fully opened, the refrigeration cycle apparatus 100 can be operated without the regulating valve 6 affecting the discharge temperature and discharge pressure of the compressor 1.

[0041] Furthermore, in this embodiment, a condenser fan 8 is provided that sends air to the condenser 2, and the control device 15 controls the target rotation speed of the condenser fan 8 based on a comparison between the second condensing temperature of the refrigerant in the condenser 2 and a second target condensing temperature. When the target rotation speed of the condenser fan 8 becomes zero, the control device 15 starts the first control and controls the aperture of the adjustment valve 6. Typically, when the discharge temperature and discharge pressure of the compressor 1 decrease due to a drop in the ambient temperature, and the second condensing temperature becomes lower than the second target condensing temperature, causing the target rotation speed of the condenser fan 8 to become zero, the control device 15 controls the aperture of the adjustment valve 6 to become smaller. In this way, the start timing of the first control can be controlled based on the target rotation speed of the condenser fan 8.

[0042] Furthermore, after starting the first control, the control device 15 may set the target rotation speed of the condenser fan 8 to zero until the opening of the regulating valve 6 reaches its maximum opening. Specifically, for example, between steps S1 and S2 in FIG. 3 , a process is executed to set the target rotation speed of the condenser fan 8 to zero if the opening of the regulating valve 6 is less than its maximum opening. In this manner, after the opening of the regulating valve 6 decreases, the condenser fan 8 remains stopped until the opening of the regulating valve 6 returns to its maximum opening. This reduces the frequency of the condenser fan 8 starting and stopping in a short period of time. Without control to keep the condenser fan 8 stopped, the target rotation speed of the condenser fan 8 becomes zero when the second condensing temperature falls below the second target condensing temperature due to low outdoor air temperature, etc. Then, when the second condensing temperature rises above the second target condensing temperature immediately thereafter, the condenser fan 8 starts operating. This results in the condenser fan 8 repeatedly starting and stopping in a short period of time, making it difficult to achieve stable refrigeration cycle performance. However, according to this embodiment, the condenser fan 8 can be prevented from being started and stopped in a short period of time, so that a stable refrigeration cycle capacity can be obtained.

[0043] Second Embodiment This embodiment differs from the first embodiment in the method of calculating the second condensing temperature. In this embodiment, the differences from the first embodiment will be mainly described.

[0044] 4 is a diagram showing a configuration example of a refrigeration cycle apparatus 100A according to Embodiment 2. The refrigeration cycle apparatus 100A according to this embodiment does not include the second pressure sensor 13 shown in Embodiment 1, and the measurement result of the second temperature sensor 14 is used as the second condensing temperature. When the refrigerant downstream of the radiator 5 is in a gas-liquid two-phase state, the second condensing temperature of the condenser 2 is the same as the refrigerant temperature measured by the second temperature sensor 14. Therefore, it is not necessary to calculate the second condensing temperature from the measurement result of the second pressure sensor 13 as in Embodiment 1.

[0045] Whether the refrigerant downstream of the radiator 5 reaches a gas-liquid two-phase state depends on the circulation rate of the pump 21, which circulates the heat medium that exchanges heat with the refrigerant in the radiator 5, the target temperature of the heat medium, etc. Therefore, the refrigeration cycle apparatus 100A controls the heat medium heat exchange rate and the refrigerant heat exchange rate so that the refrigerant downstream of the radiator 5 reaches a gas-liquid two-phase state. Specifically, the heat medium heat exchange rate and the refrigerant heat exchange rate when the heat medium is water can be obtained as follows.

[0046] Heat transfer medium heat exchange amount = Water side enthalpy difference (enthalpy after heat exchange (calculated from temperature of about room temperature + 10°C and water pressure) - enthalpy before heat exchange (calculated from temperature of about room temperature and water pressure)) x pump circulation amount

[0047] Refrigerant heat exchange amount = Refrigerant side enthalpy difference (enthalpy before heat exchange (compressor discharge enthalpy) - enthalpy after heat exchange) x refrigerant circulation amount

[0048] The room temperature used to calculate the heat medium heat exchange amount is obtained from a temperature sensor (not shown) installed in the room where the load-side heat exchanger 22 is installed, and the water pressure is obtained from a pressure sensor (not shown) installed in the water pipe of the heat medium circuit 20. Since the heat medium heat exchange amount = the refrigerant heat exchange amount, the enthalpy after heat exchange can be calculated, and the two-phase state of the refrigerant can be determined on a Mollier diagram from the compressor discharge pressure and the enthalpy after heat exchange. Then, the circulation amount of the pump 21 in the heat medium circuit 20 and the target temperature of the heat medium are controlled so that the refrigerant downstream of the radiator 5 is in a gas-liquid two-phase state.

[0049] According to the refrigeration cycle device 100A of this embodiment, the second condensing temperature can be obtained using the second temperature sensor 14, so the number of parts and manufacturing costs can be reduced compared to when the second pressure sensor 13 is provided.

[0050] Embodiment 3 This embodiment differs from Embodiments 1 and 2 in the method of measuring the temperature of the refrigerant between the radiator 5 and the condenser 2. In this embodiment, the differences from Embodiments 1 and 2 will be mainly described.

[0051] FIG. 5 is a diagram showing a configuration example of a refrigeration cycle apparatus 100B according to a third embodiment. The refrigeration cycle apparatus 100B of this embodiment does not include the second temperature sensor 14 shown in the first and second embodiments. The refrigeration cycle apparatus 100B controls the heat medium heat exchange amount and the refrigerant heat exchange amount so that the refrigerant downstream of the radiator 5 is in a two-phase gas-liquid state. As described in the second embodiment, when the refrigerant downstream of the radiator 5 is in a two-phase gas-liquid state, the temperature of the refrigerant downstream of the radiator 5 is the same as the second condensing temperature obtained from the measurement result of the second pressure sensor 13. Therefore, the temperature of the refrigerant flowing into the condenser 2 can be measured without providing the second temperature sensor 14.

[0052] According to the refrigeration cycle device 100B of this embodiment, the temperature of the refrigerant flowing into the condenser 2 can be obtained using the second pressure sensor 13, thereby reducing the number of parts and manufacturing costs compared to when a second temperature sensor 14 is provided.

[0053] REFRIGERATED SYSTEM, 64 STEP, 100 REFRIGERATED CYCLE APPARATUS, 100A REFRIGERATED CYCLE APPARATUS, 100B REFRIGERATED CYCLE APPARATUS.

Claims

1. A refrigeration cycle device comprising: a refrigerant circuit having a compressor, a condenser, an evaporator, and a pressure reducing device for circulating a refrigerant; a radiator disposed in the refrigerant circuit between the compressor and the condenser and for effecting heat exchange between the refrigerant and a heat medium; a regulating valve disposed in the refrigerant circuit between the radiator and the condenser, the regulating valve having an adjustable opening; and a control device for controlling the opening of the regulating valve based on a result of a comparison between a first condensing temperature of the refrigerant in the radiator and a first target condensing temperature.

2. The refrigeration cycle device according to claim 1, wherein the control device executes a first control to reduce the opening of the regulating valve when the first condensing temperature is lower than the first target condensing temperature, and to increase the opening of the regulating valve when the first condensing temperature is higher than the first target condensing temperature.

3. A refrigeration cycle device as described in claim 2, further comprising a condenser fan for blowing air to the condenser, wherein the control device controls a target rotation speed of the condenser fan based on a comparison between a second condensing temperature of the refrigerant in the condenser and a second target condensing temperature, and starts the first control when the target rotation speed of the condenser fan becomes zero.

4. A refrigeration cycle device as described in claim 3, wherein the control device sets the target rotation speed of the condenser fan to zero after starting the first control until the opening of the regulating valve reaches a maximum opening.

5. A refrigeration cycle device as described in claim 3 or claim 4, wherein the second condensation temperature is calculated based on either a pressure sensor provided between the radiator and the condenser for detecting the pressure of the refrigerant, or a temperature sensor provided between the radiator and the condenser for detecting the temperature of the refrigerant.

6. A refrigeration cycle device according to any one of claims 1 to 5, further comprising a load-side heat exchanger for exchanging heat between the heat medium, which has exchanged heat with the refrigerant in the radiator, and air.

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