Air conditioner

Abstract

An air conditioner according to an embodiment of the present invention includes: a refrigerant circuit; a first temperature detector; a first pressure detector; and a control device. The first temperature detector detects a temperature of a refrigerant that has flowed out from an inter-refrigerant heat exchanger and introduced into an intermediate-pressure portion of a compressor. The first pressure detector detects a pressure of the refrigerant that has flowed out from the inter-refrigerant heat exchanger and introduced into the intermediate-pressure portion of the compressor. The control device controls the degree of opening of an injection control valve such that a specific enthalpy of the refrigerant calculated on the basis of a refrigerant temperature detected by the first temperature detector and a refrigerant pressure detected by the first pressure detector is a specific enthalpy target value at which the degree of dryness of the refrigerant at a merging point between the injection pipe and the intermediate-pressure portion of the compressor is one.

1 . An air conditioner, comprising:
 a refrigerant circuit that includes a compressor, an outdoor heat exchanger, an indoor heat exchanger, a pressure reducer that is disposed between the outdoor heat exchanger and the indoor heat exchanger, a four-way valve that switches a flow direction of a refrigerant that is a non-azeotropic mixed refrigerant discharged from the compressor, an injection control valve that reduces a pressure of a first refrigerant that is part of a refrigerant condensed in the outdoor heat exchanger during a cooling operation, an inter-refrigerant heat exchanger that exchanges heat between the first refrigerant whose pressure has been reduced by the injection control valve and a second refrigerant that is a remainder of the refrigerant condensed in the outdoor heat exchanger, and an injection pipe that guides the first refrigerant that has flowed out from the inter-refrigerant heat exchanger to an intermediate-pressure portion of the compressor;   a first temperature detector that detects a temperature of the first refrigerant that has flowed out from the inter-refrigerant heat exchanger and introduced into the intermediate-pressure portion of the compressor;   a first pressure detector that detects a pressure of the first refrigerant that has flowed out from the inter-refrigerant heat exchanger and introduced into the intermediate-pressure portion of the compressor; and   a control device that controls the degree of opening of the injection control valve such that a specific enthalpy of the first refrigerant calculated on a basis of a refrigerant temperature detected by the first temperature detector and a refrigerant pressure detected by the first pressure detector is a specific enthalpy target value at which the degree of dryness of a third refrigerant that is a refrigerant at a merging point between the injection pipe and the intermediate-pressure portion of the compressor is one.   
     
     
         2 . The air conditioner according to  claim 1 , further comprising:
 a second temperature detector that detects a temperature of a refrigerant sucked into the compressor; and   a second pressure detector that detects a pressure of a refrigerant sucked into the compressor,   the control device
 calculating a refrigerant temperature in the intermediate-pressure portion of the compressor on a basis of a refrigerant temperature detected by the second temperature detector, a refrigerant pressure detected by the first pressure detector, and a refrigerant pressure detected by the second pressure detector, 
 calculating a specific enthalpy corresponding to the degree one of dryness of the third refrigerant on a basis of a specific enthalpy of a refrigerant in the intermediate-pressure portion of the compressor calculated on a basis of the refrigerant pressure detected by the first pressure detector and the refrigerant temperature in the intermediate-pressure portion of the compressor, and 
 calculating the specific enthalpy target value of the first refrigerant on a basis of a specific enthalpy of the refrigerant in the intermediate-pressure portion of the compressor and the specific enthalpy corresponding to the degree one of dryness of the third refrigerant. 
   
     
     
         3 . The air conditioner according to  claim 1 , further comprising:
 a third pressure detector that detects a pressure of a refrigerant discharged from the compressor;   a third temperature detector that detects a temperature of a refrigerant flowing out from the outdoor heat exchanger during the cooling operation; and   a fourth temperature detector that detects a temperature of the second refrigerant flowing out from the inter-refrigerant heat exchanger during the cooling operation,   the control device
 calculating a specific enthalpy of the refrigerant flowing out from the outdoor heat exchanger during the cooling operation on a basis of a pressure detected by the third pressure detector and a temperature detected by the third temperature detector, 
 calculating a specific enthalpy of the second refrigerant flowing out from the inter-refrigerant heat exchanger during the cooling operation on a basis of the pressure detected by the third pressure detector and a temperature detected by the fourth temperature detector, and 
 calculating an injection ratio that is a ratio of the first refrigerant to the second refrigerant on a basis of the specific enthalpy of the first refrigerant, the specific enthalpy of the refrigerant flowing out from the outdoor heat exchanger during the cooling operation, and the specific enthalpy of the second refrigerant flowing out from the inter-refrigerant heat exchanger during the cooling operation. 
   
     
     
         4 . The air conditioner according to  claim 3 , wherein
 the control device controls the degree of opening of the injection control valve such that the injection ratio is a target injection ratio when the specific enthalpy of the first refrigerant is the specific enthalpy target value.