Refrigeration system

Abstract

A refrigeration system utilizes a Brayton cycle which generates cold heat by using a refrigerant compressed by a compressor unit arranged on a refrigerant path. The compressor unit includes: a plurality of compressors arranged in parallel to each other on the refrigerant path; a plurality of first motors for driving the plurality of compressors, respectively; an expander-integrated compressor configured integrally with an expander; and a second motor for driving the expander-integrated compressor. The number of compressors is larger than the number of expander-integrated compressors.

1 - 8 . (canceled) 
     
     
         9 . A refrigeration system utilizing a Brayton cycle which generates cold heat by using a refrigerant compressed by a compressor unit arranged on a refrigerant path,
 wherein the compressor unit includes:
 a plurality of compressors arranged in parallel to each other on the refrigerant path; 
 a plurality of first motors for driving the plurality of compressors, respectively; 
 an expander-integrated compressor configured integrally with an expander capable of expanding the refrigerant compressed by the compressor unit; and 
 a second motor for driving the expander-integrated compressor, and 
   wherein the number of the plurality of compressors is larger than the number of the expander-integrated compressor.   
     
     
         10 . The refrigeration system according to  claim 9 ,
 wherein the plurality of first motors and the second motor are common.   
     
     
         11 . The refrigeration system according to  claim 9 , comprising a control device for controlling the plurality of compressors,
 wherein the control device is configured to control the plurality of compressors to operate some of the plurality of compressors, based on a temperature of the refrigerant at an inlet of the expander at startup of the refrigeration system.   
     
     
         12 . The refrigeration system according to  claim 11 ,
 wherein the control device is configured to perform control to decrease a rotational speed of an operating compressor and then control to change the number of operating compressors of the plurality of compressors.   
     
     
         13 . The refrigeration system according to  claim 9 ,
 wherein the refrigerant path includes:
 a bypass line connecting upstream and downstream sides of a compressor of the expander-integrated compressor to bypass the compressor, and 
 a bypass valve disposed on the bypass line. 
   
     
     
         14 . The refrigeration system according to  claim 13 ,
 wherein the bypass valve is configured to set a flow rate of the refrigerant in the compressor of the expander-integrated compressor to a predetermined value or more, based on a temperature of the refrigerant at an inlet of the expander.   
     
     
         15 . The refrigeration system according to  claim 14 ,
 wherein a rotational speed of the compressor or the expander-integrated compressor is controlled in cooperation with an opening degree of the bypass valve so that a cooling rate of the refrigerant is substantially constant.   
     
     
         16 . The refrigeration system according to  claim 9 ,
 wherein each of the plurality of compressors is a common-shaft compressor including a plurality of compressors connected in series on the refrigerant path.   
     
     
         17 . The refrigeration system according to  claim 9 ,
 wherein the plurality of first motors and the second motor each include:
 output shafts with identical shaft diameters to each other; 
 bearings supporting the output shafts with identical specifications to each other; and 
 motor casings with identical specifications to each other. 
   
     
     
         18 . The refrigeration system according to  claim 17 ,
 wherein the plurality of compressors and the expander-integrated compressor each include:
 compressor impellers with different shapes from each other; and 
 compressor impeller casings with different specifications from each other.