Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus includes a compressor, a radiator, an expander, an evaporator, a bypass circuit, and an injection circuit. The bypass circuit has a flow rate control valve and a gas-liquid separator. One end of the bypass circuit is connected to an intake conduit of the expander and the other end thereof is connected to a discharge conduit of the expander so that a portion of refrigerant passed through the radiator bypasses the expander and is guided to the flow rate control valve and that the liquid refrigerant separated by the gas-liquid separator returns to the discharge conduit of the expander. One end of the injection circuit is connected to a gas outlet portion of the gas-liquid separator and the other end thereof is connected to an intermediate pressure portion of the compressor.

1 . A refrigeration cycle apparatus comprising: 
 a compressor for compressing a refrigerant;    a radiator for cooling the refrigerant compressed by said compressor;    an expander for expanding the refrigerant cooled by said radiator and recovering mechanical power from the refrigerant under expansion;    an evaporator for heating the refrigerant expanded by said expander and supplying the refrigerant to said compressor;    a bypass circuit including a flow rate control valve and a gas-liquid separator that is provided downstream from said flow rate control valve and that is for separating the refrigerant passed through said flow rate control valve into a gas refrigerant and a liquid refrigerant, one end of said bypass circuit being connected to an intake conduit of said expander and the other end of said bypass circuit being connected to a discharge conduit of said expander so that a portion of the refrigerant passed through said radiator bypasses said expander and is guided to said flow rate control valve and that the liquid refrigerant separated by said gas-liquid separator returns to said discharge conduit of said expander; and    an injection circuit, one end of which being connected to a gas outlet portion of said gas-liquid separator and the other end of which being connected to an intermediate pressure portion of said compressor.    
     
     
         2 . The refrigeration cycle apparatus according to  claim 1 , wherein said compressor and said expander are coupled uniaxially to a motor for driving said compressor.  
     
     
         3 . The refrigeration cycle apparatus according to  claim 1 , wherein: 
 said intermediate pressure portion of said compressor is a portion facing a compression chamber of said compressor; and    the gas refrigerant that flows out of said gas-side discharge portion of said gas-liquid separator passes through said injection circuit, is injected into said compression chamber, and is mixed with the refrigerant under compression.    
     
     
         4 . The refrigeration cycle apparatus according to  claim 1 , wherein: 
 said compressor is a multi-stage compressor comprising a low-pressure-side compressor and a high-pressure-side compressor; and    said intermediate pressure portion of said compressor is a joint portion where said low-pressure-side compressor and said high-pressure-side compressor are connected.    
     
     
         5 . The refrigeration cycle apparatus according to  claim 1 , wherein said injection circuit comprises a second flow rate control valve.  
     
     
         6 . The refrigeration cycle apparatus according to  claim 1 , wherein said bypass circuit further comprises a throttling device provided downstream from said gas-liquid separator.  
     
     
         7 . The refrigeration cycle apparatus according to  claim 1 , further comprising: 
 an intake temperature sensor for detecting a temperature of the refrigerant after flowing out of said evaporator but before being taken into said compressor; and    a controller for controlling an opening of said flow rate control valve according to a detection result detected by said intake temperature sensor.    
     
     
         8 . The refrigeration cycle apparatus according to  claim 5 , further comprising: 
 an outlet temperature sensor for detecting a temperature of the refrigerant after being discharged from said compressor but before flowing into said radiator; and    a controller for controlling an opening of said second flow rate control valve according to a detection result detected by said outlet temperature sensor.    
     
     
         9 . A refrigeration cycle apparatus comprising: 
 a compressor for compressing a refrigerant;    a radiator for cooling the refrigerant compressed by said compressor;    an expander for expanding the refrigerant cooled by said radiator and recovering mechanical power from the refrigerant under expansion;    an evaporator for heating the refrigerant expanded by said expander and supplying the refrigerant to said compressor;    a bypass circuit including a flow rate control valve, one end of said bypass circuit being connected to an intake conduit of said expander and the other end of said bypass circuit being connected to an intermediate pressure portion of said compressor so that a portion of the refrigerant passed through said radiator bypasses said expander and is guided to said flow rate control valve;    an intake temperature sensor for detecting the refrigerant after flowing out of said evaporator but before being taken into said compressor; and    a controller for controlling an opening of said flow rate control valve according to a detection result detected by said intake temperature sensor.