Refrigerant system with variable capacity expander

Abstract

A refrigerant system incorporates a variable capacity expander. A bypass line selectively bypasses at least a portion of the refrigerant approaching the expander to the intermediate expansion point within the expander. In this manner, the refrigerant expansion process is controlled more efficiently than in the prior art.

1 . A refrigerant system comprising:
 a compressor, said compressor compressing a refrigerant and delivering this refrigerant to a downstream heat rejection heat exchanger, refrigerant from the heat rejection heat exchanger passing through an expander, said expander being operable to recover at least a portion of work from the refrigerant expansion process, and   a bypass line for selectively bypassing at least a portion of refrigerant from a point upstream of said expander to an intermediate pressure point in said expander.   
   
   
       2 . The refrigerant system as set forth in  claim 1 , wherein said bypass line has a refrigerant flow restriction. 
   
   
       3 . The refrigerant system as set forth in  claim 2 , wherein said refrigerant flow restriction is a valve. 
   
   
       4 . The refrigerant system as set forth in  claim 3 , wherein the valve is an on/off valve. 
   
   
       5 . The refrigerant system as set forth in  claim 4 , wherein said on/off valve has capability to rapidly cycle between on and off positions. 
   
   
       6 . The refrigerant system as set forth in  claim 5 , wherein said cycle rate of said valve is between 1 second and 60 seconds. 
   
   
       7 . The refrigerant system as set forth in  claim 2 , wherein said refrigerant flow restriction has a variable restriction area. 
   
   
       8 . The refrigerant system as set forth in  claim 1 , wherein said recovered portion of work from the refrigerant expansion process is utilized to assist in driving at least one of refrigerant system components. 
   
   
       9 . The refrigerant system as set forth in  claim 8 , wherein said system component is said compressor. 
   
   
       10 . The refrigerant system as set forth in  claim 1 , wherein said expander consists of multiple expansion stages. 
   
   
       11 . The refrigerant system as set forth in  claim 10 , wherein at least one of said expansion stages is an independent expander. 
   
   
       12 . The refrigerant system as set forth in  claim 10 , wherein said bypass line bypasses the refrigerant from an upstream location of one of said expansion stages to an upstream location of a downstream one of said expansion stages. 
   
   
       13 . The refrigerant system as set forth in  claim 10 , wherein there are multiple bypass lines between said expansion stages. 
   
   
       14 . The refrigerant system as set forth in  claim 1 , wherein said refrigerant is CO 2 . 
   
   
       15 . The refrigerant system as set forth in  claim 1 , wherein the recovered work is utilized to power another component by providing at least one of rotational energy and electrical power. 
   
   
       16 . A method of operating a refrigerant system including the steps of:
 (1) compressing a refrigerant and delivering this refrigerant to a downstream heat rejection heat exchanger, refrigerant from the heat rejection heat exchanger passing through an expander, said expander being operable to recover at least a portion of work from the refrigerant expansion process; and   (2) selectively bypassing at least a portion of refrigerant from a point upstream of said expander to an intermediate pressure point in said expander.   
   
   
       17 . The method as set forth in  claim 16 , wherein a valve controlling the selective bypassing is rapidly cycled between on and off positions. 
   
   
       18 . The method as set forth in  claim 17 , wherein a cycle rate of said valve is between 1 second and 60 seconds. 
   
   
       19 . The method as set forth in  claim 16 , wherein said recovered portion of work from the refrigerant expansion process is utilized to assist in driving at least one of refrigerant system components. 
   
   
       20 . The method as set forth in  claim 18 , wherein said bypass line bypasses the refrigerant from an upstream location of one of said expansion stages to an upstream location of a downstream one of said expansion stages.