JP2012132578A - Refrigerating cycle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem with controlling a degree of superheat at a suction port of a compressor, wherein using a pressure sensor is costly, the response is complicated, and decompostion of HFO refrigerant can be accelerated by a rise of discharge temperature of the compressor.SOLUTION: A refrigerating cycle device is provided with: a discharge temperature sensor 122 for detecting the temperature of a refrigerant discharged from the compressor 111; an outdoor heat exchange temperature sensor 123, which is a condensation temperature sensor for detecting the condensation temperature in an outdoor heat exchanger 112; and a low pressure side temperature sensor 124 for detecting the refrigerant temperature at a low pressure side port of an internal heat exchanger 121. A control device 125 regulates opening of an expansion valve 114 based on a rotation rate of the compressor 111 and an output value of the discharge temperature sensor 122, outdoor heat exchange temperature sensor 123 and the low pressure side temperature sensor 124. Thereby, the inexpensive device with high performance and high reliability is provided.

Description

  The present invention relates to a refrigeration cycle apparatus that forms a heat pump cycle using a refrigerant and performs refrigerant heating, and particularly in an apparatus that forms a cycle by connecting an indoor unit and an outdoor unit with a connecting pipe, a double bond between carbons When using a refrigerant having the above, there is provided a technique capable of reducing the pressure loss of the connecting pipe with an inexpensive configuration and suppressing the temperature rise of the compressor to prevent the refrigerant from being decomposed.

  In recent years, global warming has become a major problem, and the movement to use refrigerants with low global warming potential has become prominent. Natural refrigerants and refrigerants such as hydrofluoroolefins having a double bond between carbon and carbon have been used. Attention has been paid.

  Hydrofluoroolefin has attracted particular attention as an alternative refrigerant for R134a, and its practical application to an air conditioner for automobiles is being promoted. The warming potential (100 years) is 4 in the case of HFO-1234yf, which is extremely smaller than 1,300 of R134a and 1730 of R410A used in air conditioners and the like. This characteristic that the warming coefficient is small is attributed to the fact that there is a double bond between carbon and it is easy to decompose.

  When HFO1234yf and R410A are compared, HFO-1234yf is superior to R410A in terms of thermophysical properties, and the performance of the theoretical cycle is good. On the other hand, since the boiling point is high and the pressure loss is large, the performance of the separation type room air conditioner is remarkably reduced. Moreover, since it is easy to decompose | disassemble, it has the characteristics that it is desirable to drive | operate so that it may not become as high temperature as possible.

  In order to reduce the pressure loss, in the conventional technology, there is an air conditioner that makes the refrigerant flowing through the gas side connecting pipe (gas side connecting pipe) wet (for example, see Patent Document 1). In FIG. 4, the air conditioner 10 is configured by connecting an outdoor unit 11 and an indoor unit 12 with a liquid side communication pipe 21 and a gas side communication pipe 22. The outdoor unit 11 is provided with a compressor 31, an outdoor heat exchanger 32, an expansion valve 33, a closing valve 23, and a liquid gas heat exchanger 50 that is an internal heat exchanger for exchanging heat within the cycle. Is provided with an indoor heat exchanger 41 and a joint 24.

  The air conditioner 10 is controlled so that the outlet (point E) of the indoor heat exchanger 41 that is an evaporator is in a wet state during operation. And the liquid gas heat exchanger 50 is provided so that it may become a dry state of 5 degreeC of superheat by the suction | inhalation (A point) of the compressor 31, and the outdoor heat exchanger which is a condenser with the wet refrigerant | coolant which returned to the outdoor unit 11 Heat is exchanged with the refrigerant that has exited 32.

  Patent Document 1 does not mention a specific means for controlling the degree of superheat at the suction of the compressor 31 to a predetermined value, but as this technique, for example, there is one described in Patent Document 2 .

  FIG. 5 is a refrigeration apparatus that includes a compressor 1, a condenser 2, an expansion valve 3, and a water-side heat exchanger 4, and produces cold water by the water-side heat exchanger 4. Between the water-side heat exchanger 4 and the suction port of the compressor 1, a suction pipe heat exchanger 5 for exchanging heat with the refrigerant at the outlet of the condenser 2 and a sensor 6 for detecting the pressure and temperature of the refrigerant are arranged. .

The suction pipe heat exchanger 5 functions in the same manner as the liquid gas heat exchanger 50 in FIG. 4, and ensures the degree of superheat of the compressor suction port while making maximum use of the water-side heat exchanger 4. is there. And the pressure and temperature of a refrigerant | coolant are detected with the sensor 6, and the opening degree of the expansion valve 3 is adjusted so that a superheat degree may become a predetermined value.

JP 2009-250592 A Japanese Patent Laid-Open No. 2005-83608

  In the above conventional technique, the control is performed so that the degree of superheat of the compressor suction port becomes a predetermined value, and it is necessary to detect the pressure and temperature, and the sensor for pressure detection is expensive. was there.

  In the conventional technology, control is performed so that the superheat degree of the compressor intake port becomes a predetermined value. However, the superheat degree of the compressor intake port is complicated in response, and in the wet state, the expansion valve is opened. Even if the degree is closed, hunting is likely to occur because a change does not appear easily or a large change occurs with a small amount of opening operation. Furthermore, in the case of an air conditioner, overshoot is likely to occur in a transient state due to changes in the air volume of the indoor unit, changes in the rotational speed of the compressor, and the like.

  If the superheat degree of the suction is taken too much, the discharge temperature of the compressor rises and the refrigerant having poor stability such as HFO-1234yf may accelerate the decomposition of the refrigerant due to the temperature rise.

  Accordingly, the present invention solves these problems, and in a refrigeration cycle apparatus using a hydrofluoroolefin such as HFO-1234yf or HFO-1234ze as a refrigerant, reduces the pressure loss and realizes excellent operation efficiency with an inexpensive configuration. By suppressing the temperature rise of the compressor, decomposition of the refrigerant is prevented and a highly reliable device is provided.

  In order to solve the above conventional problems, the refrigeration cycle apparatus of the present invention uses hydrofluoroolefin as a refrigerant, a compressor, a condenser, an expansion valve, an evaporator, and a refrigerant at the outlet of the condenser. An internal heat exchanger that exchanges heat with the refrigerant that returns from the evaporator and is sucked into the suction port of the compressor, a discharge temperature sensor that is provided at the discharge port of the compressor, and a condensation that is provided in the condenser A temperature sensor, a low-pressure side temperature sensor provided at a low-pressure side inlet of the internal heat exchanger, and a control means. The control means expands using outputs of the condensation temperature sensor, the low-pressure side temperature sensor, and the discharge temperature sensor. It adjusts the opening of the valve.

  Thereby, the opening degree of an expansion valve can be adjusted, without detecting the pressure of the refrigerant | coolant in the inlet of a compressor.

  In the refrigeration cycle apparatus of the present invention, the control means determines a target value of the output of the discharge temperature sensor based on the output of the condensation temperature sensor, the low-pressure side temperature sensor, and the rotation speed of the compressor, The opening of the expansion valve is adjusted so that the output of the temperature sensor matches the target value.

  As a result, control is performed so that the output of the discharge temperature sensor provided at the discharge port of the compressor where the temperature of the refrigerant becomes highest outside the inside of the compressor becomes the target value, so that the rise in the temperature of the refrigerant is surely suppressed. Can do.

The refrigeration cycle apparatus of the present invention reduces pressure loss with an inexpensive configuration that does not require detection of the refrigerant pressure, achieves excellent operating efficiency, and can reliably suppress the temperature rise of the refrigerant. And a highly reliable device can be provided.

Cycle configuration diagram of refrigeration cycle apparatus in Embodiment 1 of the present invention Ph diagram of the refrigeration cycle apparatus in Embodiment 1 of the present invention Cycle configuration diagram of refrigeration cycle apparatus in Embodiment 2 of the present invention Cycle configuration diagram of conventional refrigeration cycle equipment Cycle configuration diagram of conventional refrigeration cycle equipment

  The first invention uses hydrofluoroolefin as a refrigerant, returns from the compressor, the condenser, the expansion valve, the evaporator, the refrigerant at the outlet of the condenser, and the evaporator to the suction port of the compressor. An internal heat exchanger for exchanging heat with the sucked refrigerant, a discharge temperature sensor provided at the discharge port of the compressor, a condensation temperature sensor provided at the condenser, and a low-pressure side inlet of the internal heat exchanger The low-pressure side temperature sensor and the control means are provided, and the control means adjusts the opening degree of the expansion valve using the outputs of the condensing temperature sensor, the low-pressure side temperature sensor, and the discharge temperature sensor.

  Thereby, the opening degree of an expansion valve can be adjusted, without detecting the pressure of the refrigerant | coolant in the inlet of a compressor.

  Therefore, since it is not necessary to detect the pressure of the refrigerant, it can be configured at low cost. For this reason, it is possible to reduce pressure loss with an inexpensive configuration and realize excellent operation efficiency, and to reliably suppress an increase in the temperature of the refrigerant. Therefore, it is possible to suppress the decomposition of the refrigerant and provide a highly reliable device. be able to.

  In a second aspect of the invention, in particular, in the first aspect of the invention, the control means determines a target value of the output of the discharge temperature sensor based on the output of the condensation temperature sensor, the low-pressure side temperature sensor, and the rotation speed of the compressor, The opening of the expansion valve is adjusted so that the output of the discharge temperature sensor matches the target value.

  As a result, control is performed so that the output of the discharge temperature sensor provided at the discharge port of the compressor where the temperature of the refrigerant becomes highest outside the inside of the compressor becomes the target value, so that the rise in the temperature of the refrigerant is surely suppressed. Can do.

  Therefore, decomposition of the refrigerant can be suppressed and a highly reliable device can be provided.

  In a third aspect of the invention, particularly in the second aspect of the invention, the heat exchange capacity of the internal heat exchanger and / or the target value of the discharge temperature sensor are set so that the refrigerant is in a two-phase state at the low pressure side inlet of the internal heat exchanger. It is to set.

  As a result, the pressure loss from the evaporator outlet to the low pressure side inlet of the internal heat exchanger can be reduced, and the saturation temperature at the compressor inlet can be accurately detected.

  Therefore, high driving efficiency can be realized.

  According to a fourth invention, in the second invention, the opening operation amount of the expansion valve when the output of the discharge temperature sensor is higher than the target value, and the opening operation when the output of the discharge temperature sensor is lower than the target value It must be larger than the amount.

  Thereby, it can prevent that the temperature of a refrigerant | coolant rises excessively, and when it rises excessively, it can be dropped rapidly.

  Therefore, the decomposition of the refrigerant can be suppressed with higher accuracy, and the reliability of the apparatus can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a cycle configuration diagram of an air conditioner that is a refrigeration cycle apparatus according to a first embodiment of the present invention.

  As shown in FIG. 1, the air conditioner in the first embodiment is configured by connecting an outdoor unit 100 and an indoor unit 101 with connection pipes, that is, a liquid side connection pipe 126 and a gas side connection pipe 127. ing. As the refrigerant, HFO-1234yf, which is a hydrofluoroolefin having a double bond between carbons and having a small warming potential, is used.

  The outdoor unit 100 includes a compressor 111, an outdoor heat exchanger 112 that is a condenser, an outdoor fan 113, an expansion valve 114 that decompresses and expands the refrigerant, an accumulator 117, a refrigerant on the high-pressure side that exits the outdoor heat exchanger 112, and an indoor unit. An internal heat exchanger 121 that exchanges heat with the low-pressure refrigerant returned from the machine 101, a discharge temperature sensor 122 that detects the temperature of the refrigerant discharged from the compressor 111, and the outdoor heat exchanger 112. An outdoor heat exchanger temperature sensor 123 that is a condensation temperature sensor that detects the condensation temperature, a low-pressure temperature sensor 124 that detects the refrigerant temperature at the low-pressure inlet of the internal heat exchanger 121, the rotational speed of the compressor 111, and the discharge temperature. A control device 125 that adjusts the opening degree of the expansion valve 114 based on output values of the sensor 122, the outdoor heat exchange temperature sensor, and the low-pressure side temperature sensor 124 is provided.

  The indoor unit 101 includes an indoor heat exchanger 115 that is an evaporator and an indoor blower 116.

  The compressor 111, the outdoor heat exchanger 112, the expansion valve 114, the liquid side connection pipe 126, the indoor heat exchanger 115, the gas side connection pipe 127, and the accumulator 117 are connected in a ring shape to form a refrigeration cycle. The internal heat exchanger 121 is configured such that heat is exchanged between the refrigerant between the outdoor heat exchanger 112 and the expansion valve 114 and the refrigerant between the gas side connection pipe 127 and the accumulator 117.

  When the internal heat exchanger 121 is used at a position such as the internal heat exchanger 121 in FIG. 1, conventionally, the superheat degree of the suction of the compressor 111 is treated as a control target, and the pressure of the suction port of the compressor 111 is The temperature is detected and the degree of superheat is obtained, or the temperature is detected at a plurality of locations (for example, the inlet and outlet of the evaporator), the difference is calculated, and then the degree of superheat is estimated and control is performed.

  When detecting pressure, the pressure sensor is very expensive compared to the temperature sensor. In the present embodiment, since control is performed using the output of only the temperature sensor, an inexpensive configuration can be realized.

  By detecting the temperature at multiple locations (for example, at the inlet and outlet of the evaporator) and calculating the difference between them, the response is complicated, and if the degree of superheat is not taken, the degree of dryness is not known. Therefore, it is difficult to determine an appropriate operation amount, and if the degree of superheat is taken out, a large change may occur with a small amount of operation, and hunting is likely to occur, and high control cannot be expected. In the present embodiment, attention is not paid to the degree of superheat in the suction of the compressor 111, and control is performed based on the rotation speed of the compressor 111, the outputs of the discharge temperature sensor 122, the outdoor heat exchanger temperature sensor 123, and the low pressure side temperature sensor 124. Therefore, based on not only the information on the low pressure side but also the information on the high pressure side and the information on the compressor 111, highly accurate control can be performed.

  The principle of the control method of the expansion valve 114 performed by the control device 125 of the present embodiment will be described with reference to FIG. FIG. 2 is a Ph diagram of the air conditioner according to Embodiment 1 of the present invention, and is a conceptual diagram for explanation. Since there is actually a pressure loss, the high pressure is constant at Ph and the low pressure is not constant at Pl, but it is constant for convenience.

  Assuming that the air conditioner is operating ideally, point A is the state of the refrigerant at the inlet of the compressor 111 (pressure Pl, specific enthalpy hl1), and point B is the refrigerant at the outlet of the compressor 111. State (pressure Ph, specific enthalpy hh1), point C is the high-pressure side inlet of the internal heat exchanger 121, point D is the high-pressure side outlet of the internal heat exchanger 121, point E is the inlet of the indoor heat exchanger 115 which is an evaporator , F points respectively indicate the state of the refrigerant at the outlet of the indoor heat exchanger 115 as an evaporator and the low-pressure side inlet of the internal heat exchanger 121.

  The discharge temperature sensor 122 detects the temperature (discharge temperature) T1 at the discharge port of the compressor 111, the outdoor heat exchange temperature sensor 123 detects the saturation temperature of the high pressure Ph, and the low pressure side temperature sensor 124 detects the saturation temperature of the low pressure Pl. . In the present embodiment, since the low pressure side inlet of the internal heat exchanger 121 provided with the low pressure side temperature sensor 124 is the F point, the saturation temperature of the low pressure Pl can be detected.

  If the compressor 111 performs ideal adiabatic compression, the state of the discharge port of the compressor 111 is point I, but in reality it is point B. The amount of shift from point I to point B is determined by the compressor efficiency, and the compressor efficiency is determined by the specific characteristics resulting from the specifications of the compressor 111 and the rotational speed.

  In each air conditioner, the degree of superheat of the suction of the compressor 111 that maximizes the operation efficiency is determined according to the operation state. In other words, when the suction pressure of the compressor 111 is Pl and the discharge pressure is Ph, if the rotation speed of the compressor 111 is determined, the suction port state A and the discharge port state B point at which the operating efficiency is maximum are automatically set. The discharge temperature T1 can be predicted.

  The expansion valve 114 is opened and closed when the suction pressure Pl, the discharge pressure Ph of the compressor 111, and the rotation speed of the compressor 111 are the same. If the compressor 111 is closed, the degree of superheat of the suction of the compressor 111 increases and the state of the suction port is Moving from point A to point A2, point I moves to point I2, point B moves to point B2, and the discharge temperature rises from T1 to T2. When it is opened, the opposite is true, and the discharge temperature is lower than T1.

  Next, a more specific control method of the expansion valve 114 performed by the control device 125 of the present embodiment will be described.

  First, the outdoor heat exchanger temperature sensor 123 detects the temperature of the outdoor heat exchanger 112 serving as a condenser. And the control apparatus 125 estimates the high voltage | pressure Ph from the detected temperature of the outdoor heat exchanger temperature sensor 123 using the estimation formula preserve | saved previously at memory etc., or an estimation table. Next, the low pressure side temperature sensor 124 detects the temperature of the low pressure side inlet of the internal heat exchanger 121. Then, the control device 125 estimates the low pressure Pl from the detected temperature of the low pressure side temperature sensor 124 using an estimation formula or an estimation table stored in advance in a memory or the like.

  Next, the target discharge temperature is determined from the estimated high pressure Ph and low pressure Pl using the estimation formula or the estimation table stored in advance in a memory or the like and the current rotation speed of the compressor 111 as necessary. calculate. Then, the discharge temperature detected by the discharge temperature sensor 122 is compared with the target discharge temperature.

When the detected discharge temperature is higher than the target discharge temperature, the opening of the expansion valve 114 is increased by a predetermined first opening operation amount, and the expansion valve 114 is controlled to open. When the detected discharge temperature is higher than the target discharge temperature, the opening degree of the expansion valve 114 is decreased by a predetermined second opening operation amount, and the expansion valve 114 is closed. In the present embodiment, the first opening operation amount is set to be larger than the second opening operation amount.

  As described above, in the air conditioner of the present embodiment, the control device 125 estimates the high pressure from the output of the outdoor heat exchanger temperature sensor 123 and the low pressure from the output of the low pressure side temperature sensor 124, and rotates the compressor 111. The target discharge temperature is calculated from the number and the device characteristics stored in advance, and the opening degree of the expansion valve 114 is adjusted so that the output of the discharge temperature sensor 122 matches the target discharge temperature. can do.

  Here, since the control target is the discharge temperature, unlike the conventional technique in which the superheat degree of suction is set as the control target, and as a result, the discharge temperature is controlled, it is possible to reliably suppress an increase in the discharge temperature.

  When the discharge temperature is suppressed, decomposition of HFO-1234yf used as the refrigerant can be suppressed.

  In a conventional air conditioner that does not use an internal heat exchanger, an example in which discharge temperature control is performed is known, but low pressure is estimated at the temperature of the evaporator. When HFO-1234yf or the like is used, since the pressure loss is large, the temperature of the evaporator and the saturation temperature of the compressor intake port are different from each other, and particularly depending on the length of the gas side connection pipe, The difference from the saturation temperature of the compressor inlet changes greatly, and the correct target discharge temperature cannot be set. However, in the present embodiment, since the low pressure is estimated based on the temperature of the low pressure side inlet of the internal heat exchanger 121 before passing through the gas side connection pipe 127, even when HFO-1234yf or the like having a large pressure loss is used. Therefore, the target value of the discharge temperature can be set correctly.

  In addition, when using an internal heat exchanger, as described above, the superheat degree of the compressor intake port is handled as a control target, so that the low pressure side inlet of the internal heat exchanger 121 is in a two-phase state. In the past, there was no idea of improving the control accuracy. In the present embodiment, the heat exchange capacity of the internal heat exchanger 121 is sufficiently large so that the refrigerant at the low-pressure side inlet of the internal heat exchanger 121 can be in a two-phase state, and the target output value of the discharge temperature sensor 122 is also set. It sets so that the refrigerant | coolant of the low voltage | pressure side inlet_port | entrance of the internal heat exchanger 121 may be in a two-phase state.

  Therefore, the refrigerant from the outlet of the indoor heat exchanger 115 serving as an evaporator to the low-pressure side inlet of the internal heat exchanger 121 is in a two-phase state, and the flow velocity is reduced and pressure loss is reduced as compared with the case of flowing with dry gas. High operating efficiency can be realized. In addition, since the estimation error of the saturation temperature of the suction port of the compressor 111 due to the pressure loss of the gas side connection pipe 127 can be reduced, the accuracy of the target value of the discharge temperature is also improved.

  When HFO-1234yf or the like is used, discharge temperature control that can withstand use cannot be performed unless pressure loss is reduced. If the inner diameter of the gas side connection pipe 127 is increased, the pressure loss can be reduced, but the construction becomes difficult. If the pipe is long, the pressure loss is further increased. Therefore, it is very effective to use the internal heat exchanger 121 and make the low-pressure side inlet into a two-phase state as in the present invention.

  Further, the opening operation amount of the expansion valve 114 when the output of the discharge temperature sensor 122 is higher than the target value is made larger than the operation amount when the output of the discharge temperature sensor 122 is lower than the target value.

Thereby, it is possible to prevent the superheat degree of the suction of the compressor 111 from rising at a stretch and the refrigerant temperature from being excessively increased, and to rapidly decrease the refrigerant temperature when it is excessively increased.

  Therefore, the decomposition of the refrigerant can be suppressed with higher accuracy, and the reliability of the apparatus can be improved.

  In addition, although HFO-1234yf was used as the refrigerant, the same effect can be obtained regardless of whether it is HFO-1234ze or a mixed refrigerant containing HFO-1234yf or HFO-1234ze.

(Embodiment 2)
FIG. 3 is a cycle configuration diagram of an air conditioner that is a refrigeration cycle apparatus according to the second embodiment of the present invention.

  As shown in FIG. 3, a check valve bridge composed of a four-way valve 119 and four check valves is added to the air conditioner of FIG.

  The check valve bridge is provided between the first check valve 120 a provided between the outdoor heat exchanger 112 and the high pressure side of the internal heat exchanger 121, the expansion valve 114, and the liquid side connection pipe 126. The second check valve 120b, the third check valve 120c provided between the liquid side connection pipe 126 and the high pressure side of the internal heat exchanger 121, and between the expansion valve 114 and the outdoor heat exchanger 112. The fourth check valve 120d is provided.

  The first check valve 120a prevents the flow from the internal heat exchanger 121 to the outdoor heat exchanger 112, and the second check valve 120b flows from the liquid side connection pipe 126 to the expansion valve 114. It is installed in the direction to prevent. The third check valve 120c prevents the flow from the internal heat exchanger 121 to the liquid side connection pipe 126, and the fourth check valve 120d prevents the flow from the outdoor heat exchanger 112 to the expansion valve 114. It is installed in the direction to do.

  FIG. 3 shows a state during cooling. During heating, the four-way valve 119 is switched, and the internal heat exchanger 121 is located upstream of the expansion valve 114 due to the effect of the check valve bridge. During heating, the indoor heat exchanger 115 serves as a condenser, and the indoor heat exchanger temperature sensor 118 serves as a condensation temperature sensor.

  During the cooling operation, the outdoor heat exchanger 112 is a condenser and the outdoor heat exchanger temperature sensor 123 is a condensation temperature sensor as in the first embodiment.

  Other configurations and effects are the same as those in the first embodiment.

  Moreover, although HFO-1234yf was used as the refrigerant, even if it is HFO-1234ze or a mixed refrigerant containing HFO-1234yf or HFO-1234ze, the same effect can be obtained.

  The refrigeration cycle apparatus according to the present invention is based not only on information on the low pressure side but also on information on the high pressure side and information on the compressor, and can perform highly accurate control. Moreover, high operating efficiency and high reliability can be realized with a low-cost configuration for a refrigerant that has a large pressure loss and is easy to decompose. As a result, a refrigerant that is easily decomposed, such as a hydrofluoroolefin having a double bond between carbon and carbon, can be used, and the environment is excellent.

  The present invention is not limited to an air conditioner, and can be widely applied to a separate type showcase, a refrigerator, a heat pump type water heater, and the like, and brings about an effect.

DESCRIPTION OF SYMBOLS 100 Outdoor unit 101 Indoor unit 111 Compressor 112 Outdoor heat exchanger 113 Outdoor blower 114 Expansion valve 115 Indoor heat exchanger 116 Indoor blower 117 Accumulator 121 Internal heat exchanger 122 Discharge temperature sensor 123 Outdoor heat exchange temperature sensor 124 Low pressure side temperature sensor 125 Control Device 126 Liquid Side Connection Pipe 127 Gas Side Connection Pipe 120a First Check Valve 120b Second Check Valve 120c Third Check Valve 120d Fourth Check Valve

Claims (4)

Hydrofluoroolefin is used as the refrigerant, and the compressor, the condenser, the expansion valve, the evaporator, the refrigerant at the outlet of the condenser, and the refrigerant are returned from the evaporator and sucked into the suction port of the compressor. An internal heat exchanger for exchanging heat with the refrigerant, a discharge temperature sensor provided at a discharge port of the compressor, a condensation temperature sensor provided at the condenser, and a low pressure of the internal heat exchanger A low-pressure side temperature sensor provided at a side inlet; and a control unit, wherein the control unit controls an opening degree of the expansion valve using outputs of the condensation temperature sensor, the low-pressure side temperature sensor, and the discharge temperature sensor. A refrigeration cycle apparatus characterized by adjusting. The control means determines a target value of the output of the discharge temperature sensor based on the output of the condensing temperature sensor, the low pressure side temperature sensor, and the rotation speed of the compressor, and the output of the discharge temperature sensor is The refrigeration cycle apparatus according to claim 1, wherein the opening degree of the expansion valve is adjusted so as to coincide with a target value. The heat exchange capacity of the internal heat exchanger and / or the target value of the discharge temperature sensor are set so that the refrigerant is in a two-phase state at the low pressure side inlet of the internal heat exchanger. 2. The refrigeration cycle apparatus according to 2. The opening degree operation amount of the expansion valve when the output of the discharge temperature sensor is higher than the target value is made larger than the opening degree operation amount when the output of the discharge temperature sensor is lower than the target value. The refrigeration cycle apparatus according to claim 2, characterized in that: