Vapor compression type refrigerating machine

Abstract

A bypass valve 81 is opened until a predetermined period of time elapses after compressors 10 a , 10 b are stopped so as to equalize the pressure of a refrigerant circuit on a condenser 20 side with the pressure of a refrigerant circuit on an evaporator 30 side and, after the bypass valve 81 is closed, at least either of a refrigerant circuit 91 connecting to the compressor 10 a and a refrigerant circuit 92 connecting to the compressor 10 b is opened by opening a three-way valve 90 so that the refrigerant circuit on the condenser 20 side is made to communicate with the refrigerant circuit on the evaporator 30 side via the compressor 10 whereby, as the pressure equalized state can be maintained, it is possible to prevent the accumulation of a large amount of refrigerating machine oil on suction sides of the compressors 10 while the compressors 10 are stopped, thereby making it possible to prevent damage to the compressors 10 due to excessive compression when activated.

1 . A vapor compression type refrigerating machine, for moving heat on a low temperature side to a high temperature side, comprising: 
 a plurality of compressors arranged in parallel relative to the flow of a refrigerant for sucking in and compressing a refrigerant;    a high-pressure side heat exchanger for removing heat from a highly pressurized refrigerant discharged from the compressors;    a low-pressure side heat exchanger for absorbing heat by vaporizing a low pressure refrigerant;    an oil separator provided on a refrigerant inlet side of the high-pressure heat exchanger for separating and extracting a refrigerating machine oil mixed in the refrigerant;    an oil return circuit for returning the refrigerant so separated and extracted by the oil separator to suction sides of the compressors;    a bypass circuit for establishing a communication between a refrigerant circuit on a high-pressure side heat exchanger side and a refrigerant circuit on a low-pressure side heat exchanger side;    a bypass valve for opening and closing the bypass circuit;    a compressor valve for opening and closing refrigerant circuits which connect to the compressors, respectively; and    a control unit for controlling both the valves such that the bypass valve is kept open until a predetermined period of time elapses after the plurality of compressors are stopped and that, after the predetermined period of time has elapsed, the bypass valve is closed, while the compressor valve is opened.    
   
   
       2 . A vapor compression type refrigerating machine as set forth in  claim 1 , wherein the compressor valve opens and closes the refrigerant circuits which connect to discharge sides of the compressors.  
   
   
       3 . A vapor compression type refrigerating machine comprising: 
 a plurality of compressors ( 10 ) arranged in parallel relative to the flow of a refrigerant for sucking in and compressing a refrigerant;    a high-pressure side heat exchanger for removing heat from a highly pressurized refrigerant discharged from the compressors;    a low-pressure side heat exchanger for absorbing heat by vaporizing a low pressure refrigerant;    an ejector having a nozzle for converting pressure energy of the highly pressurized refrigerant that flows out from the high-pressure side heat exchanger into velocity energy so as to reduce the pressure of the refrigerant for expansion thereof and a pressure increasing portion for sucking in a vapor-phase refrigerant vaporized by a high-speed flow of refrigerant injected from the nozzle at the low-pressure side heat exchanger and mixing the refrigerant injected from the nozzle with the refrigerant sucked in from the low-pressure side heat exchanger so as to convert the velocity energy into a pressure energy to thereby increase the pressure of the refrigerant;    a vapor-liquid separator for separating the refrigerant that has flowed out from the ejector into a vapor-phase refrigerant and a liquid-phase refrigerant in which an outlet for the vapor-phase refrigerant is connected to suction sides of the compressors and an outlet for the liquid-phase refrigerant is connected to the low-pressure side heat exchanger;    an oil separator provided on a refrigerant inlet side of the high-pressure heat exchanger for separating and extracting a refrigerating machine oil mixed in the refrigerant;    an oil return circuit for returning the refrigerant so separated and extracted by the oil separator to the suction sides of the compressors;    a bypass circuit for establishing communication between a refrigerant circuit on a high-pressure side heat exchanger side and a refrigerant circuit on a low-pressure side heat exchanger side;    a bypass valve for opening and closing the bypass circuit;    a compressor valve for opening and closing refrigerant circuits which connect to the compressors, respectively; and    a control unit for controlling both the valves such that the bypass valve is kept open until a predetermined period of time elapses after the plurality of compressors are stopped and that after the predetermined period of time has elapsed, the bypass valve is closed, while the compressor valve is opened.    
   
   
       4 . A vapor compression type refrigerating machine as set forth in  claim 3 , wherein the compressor valve opens and closes the refrigerant circuits which connect to discharge sides of the compressors.