Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus ( 100 ) includes an expander-compressor unit ( 1 ) including a first compression mechanism ( 11 ) and an expansion mechanism ( 13 ), and a sub compressor ( 2 ) including a second compression mechanism ( 21 ). The first compression mechanism ( 11 ) is connected in parallel with the second compression mechanism ( 21 ) in a refrigerant circuit ( 30 ). The refrigeration cycle apparatus ( 100 ) further includes a bypass passage ( 6 ) bypassing the expansion mechanism ( 13 ). A first flow control valve ( 61 ), a gas-liquid separator ( 62 ) and a second flow control valve ( 63 ) are provided sequentially to the bypass passage ( 6 ) from an upstream side. An injection passage ( 7 ) guides a gas refrigerant separated from a liquid refrigerant in the gas-liquid separator ( 62 ) to the second compression mechanism ( 21 ).

1 . A refrigeration cycle apparatus comprising:
 an expander-compressor unit including a first compression mechanism for compressing a refrigerant, and an expansion mechanism for recovering power from the refrigerant expanding;   a sub compressor including a second compression mechanism for compressing the refrigerant, the second compression mechanism being connected in parallel with the first compression mechanism in a refrigerant circuit;   a radiator for radiating heat from the refrigerant discharged from the first compression mechanism and the second compression mechanism;   an evaporator for evaporating the refrigerant discharged from the expansion mechanism;   a first pipe for guiding the refrigerant from the first compression mechanism and the second compression mechanism to the radiator;   a second pipe for guiding the refrigerant from the radiator to the expansion mechanism;   a third pipe for guiding the refrigerant from the expansion mechanism to the evaporator;   a fourth pipe for guiding the refrigerant from the evaporator to the first compression mechanism and the second compression mechanism;   a bypass passage extending from the second pipe to the third pipe so as to bypass the expansion mechanism;   a first flow control valve, a gas-liquid separator and a second flow control valve provided sequentially to the bypass passage from an upstream side; and   an injection passage for guiding a gas refrigerant separated from a liquid refrigerant in the gas-liquid separator to the second compression mechanism.   
     
     
         2 . The refrigeration cycle apparatus according to  claim 1 , wherein the injection passage is provided with an opening and closing valve. 
     
     
         3 . The refrigeration cycle apparatus according to  claim 2 , further comprising a controller that opens the opening and closing valve and the first flow control valve when a required load is equal to or more than a specified value determined in advance. 
     
     
         4 . The refrigeration cycle apparatus according to  claim 3 , wherein:
 the radiator is a heat exchanger for exchanging heat between the refrigerant and water so as to produce hot water;   the refrigeration cycle apparatus further comprises an incoming water temperature detecting means for detecting a temperature of the incoming water to the radiator, and an outside air temperature detecting means for detecting a temperature of outside air; and   the controller calculates a proper pressure of the refrigerant to be guided to the radiator through the first pipe, based on the temperature of the incoming water detected by the incoming water temperature detecting means and the temperature of outside air detected by the outside air temperature detecting means.   
     
     
         5 . The refrigeration cycle apparatus according to  claim 4 , further comprising a pressure detecting means for detecting a pressure of a high pressure side in a refrigeration cycle,
 wherein the controller adjusts an opening of the first flow control valve so that the pressure detected by the pressure detecting means is equal to the proper pressure.   
     
     
         6 . The refrigeration cycle apparatus according to  claim 4 , further comprising a refrigerant temperature detecting means for detecting a temperature of the refrigerant being guided to the radiator through the first pipe,
 wherein the controller calculates a pressure of the refrigerant being guided to the radiator based on the temperature of the refrigerant detected by the refrigerant temperature detecting means and the temperature of outside air detected by the outside air temperature detecting means, and adjusts an opening of the first flow control valve so that the calculated pressure is equal to the proper pressure.   
     
     
         7 . The refrigeration cycle apparatus according to  claim 1 , wherein the refrigerant is carbon dioxide.