Refrigeration Cycle System and Automotive Air-Conditioning System Including the Refrigeration Cycle System

Abstract

There are provided a refrigeration cycle system which ensures adequate lubrication in a compressor and operates at a satisfactory coefficient of performance despite use of a working fluid containing a lubricant and a refrigerant that separate from each other in a condenser, and an automotive air-conditioning system including the refrigeration cycle system. A refrigeration cycle system ( 12 ) comprises a compressor ( 28 ), a condenser ( 24 ), an expansion valve ( 26 ) and an evaporator ( 28 ) disposed in a circulation path ( 14 ) along which a working fluid containing a lubricant and a refrigerant that separates from each other at temperatures higher than a two-layer separation temperature flows, serially in a specified flow direction of the working fluid, and a lubricant return means for preventing the lubricant from accumulating in the condenser ( 24 ). The lubricant return means reduces pressure of the refrigerant in the condenser ( 24 ) to a saturation pressure of the refrigerant for the two-layer separation temperature or below, when the working fluid is made to flow along the circulation path in the specified flow direction and temperature around the condenser ( 24 ) is lower than the two-layer separation temperature.

1 . A refrigeration cycle system comprising a compressor, a condenser, an expansion valve and an evaporator disposed in a circulation path along which a working fluid containing a refrigerant and a lubricant that separate from each other at temperatures higher than a two-layer separation temperature flows, serially in a specified flow direction of the working fluid, and a lubricant return means for preventing the lubricant from accumulating in the condenser, wherein
 the lubricant return means reduces pressure of the refrigerant in the condenser to a saturation pressure of the refrigerant for said two-layer separation temperature or below, when the working fluid is made to flow along the circulation path in said specified flow direction and temperature around the condenser is lower than said two-layer separation temperature.   
     
     
         2 . The refrigeration cycle system according to  claim 1 , wherein the lubricant return means includes a displacement regulation means for regulating displacement of the compressor to reduce the pressure of the refrigerant by regulating the displacement of the compressor by using the displacement regulation means. 
     
     
         3 . The refrigeration cycle system according to  claim 1 , wherein the lubricant return means further includes a flow reversing means for causing the working fluid to flow along the circulation path in a direction opposite to said specified flow direction. 
     
     
         4 . The refrigeration cycle system according to  claim 3 , wherein the flow reversing means includes a four-way switch valve disposed in the circulation path and changed between a position to connect a discharge port and a suction of the compressor to an inlet of the condenser and an outlet of the evaporator, respectively, and a position to connect the discharge port and the suction of the compressor to the outlet of the evaporator and the inlet of the condenser, respectively. 
     
     
         5 . The refrigeration cycle system according to  claim 1 , wherein the working fluid contains polyalkylene glycol as the lubricant and R1234yf as the refrigerant. 
     
     
         6 . An automotive air-conditioning system including a refrigeration cycle system according to  claim 1 .