Economized refrigerant system utilizing expander with intermediate pressure port

Abstract

A refrigerant system utilizes an expander, where at least partially expanded refrigerant portion is tapped at the intermediate expansion point and passed through an economizer heat exchanger. In the economizer heat exchanger, the tapped refrigerant further cools refrigerant in a main liquid line. The present invention eliminates the need for a separate dedicated economizer circuit expansion throttling device, by utilizing a single expander to provide this expansion function. This invention also allows for the recovery of the expansion work, otherwise lost in the economizer expansion throttling device. System capacity and efficiency are improved by providing additional thermal potential for the refrigerant expanded (partially or fully) in the expander during more efficient isentropic process. In various embodiments, there may be more than a single economizer circuit, with each of said economizer circuits receiving the tapped refrigerant portions from the expander at different intermediate expansion points.

1 . A refrigerant system comprising:
 a compressor, said compressor compressing refrigerant and delivering it downstream to a first heat exchanger, refrigerant passing from said first heat exchanger through at least one economizer heat exchanger and an expander, refrigerant expanding in said expander,   a second heat exchanger positioned downstream of said expander, and refrigerant passing from said expander through said second heat exchanger, and then back to said compressor; and   at least a portion of refrigerant being tapped from at least one location where it has been at least partially expanded in said expander, and passed through said economizer heat exchanger to cool refrigerant in a main refrigerant circuit, said tapped refrigerant portion then being returned to said compressor.   
   
   
       2 . The refrigerant system as set forth in  claim 1 , wherein said tapped refrigerant is returned to at least one intermediate compression point in said compressor. 
   
   
       3 . The refrigerant system as set forth in  claim 1 , wherein said compressor includes a first stage compressor and a second stage compressor. 
   
   
       4 . The refrigerant system as set forth in  claim 3 , wherein said returned refrigerant being returned to a point intermediate said first stage compressor and said second stage compressor. 
   
   
       5 . The refrigerant system as set forth in  claim 1 , wherein there is one said economizer heat exchanger, and at least a portion of at least partially expanded refrigerant being tapped from one location in said expander and passed through said one economizer heat exchanger. 
   
   
       6 . The refrigerant system as set forth in  claim 1 , wherein there are at least two of said economizer heat exchangers, and refrigerant being tapped from two locations in said expander and passed through said at least two economizer heat exchangers. 
   
   
       7 . The refrigerant system as set forth in  claim 6 , wherein said tapped refrigerant for said at least two economizer heat exchangers being tapped from at least two distinct locations in said expander. 
   
   
       8 . The refrigerant system as set forth in  claim 1 , wherein work of expansion is utilized to assist in driving at least one component within or outside of said refrigerant system. 
   
   
       9 . A method of operating a refrigerant system comprising the steps of:
 (a) providing a compressor, said compressor compressing refrigerant and delivering it downstream to a first heat exchanger, refrigerant passing from said first heat exchanger through at least one economizer heat exchanger, and an expander, refrigerant expanding in said expander;   (b) providing a second heat exchanger positioned downstream of said expander, and refrigerant passing from said expander through said second heat exchanger, and then back to said compressor; and   (c) tapping at least a portion of refrigerant from at least one location where it has been at least partially expanded in said expander, and passing it through said economizer heat exchanger to cool refrigerant in a main refrigerant circuit, said tapped refrigerant portion then being returned to said compressor.   
   
   
       10 . The method as set forth in  claim 9 , wherein said tapped refrigerant is returned to at least one intermediate compression point in said compressor. 
   
   
       11 . The method as set forth in  claim 9 , wherein said compressor includes a first stage compressor and a second stage compressor. 
   
   
       12 . The method as set forth in  claim 11 , wherein said returned refrigerant being returned to a point intermediate said first stage compressor and second stage compressor. 
   
   
       13 . The method as set forth in  claim 9 , wherein there is one said economizer heat exchanger, and at least a portion of at least partially expanded refrigerant being tapped from one location in said expander and passed through said one economizer heat exchanger. 
   
   
       14 . The method as set forth in  claim 9 , wherein there are at least two of said economizer heat exchangers, and refrigerant being tapped from two locations in said expander and passed through said at least two economizer heat exchangers. 
   
   
       15 . The method as set forth in  claim 14 , wherein said tapped refrigerant for said at least two economizer heat exchangers being tapped from at least two distinct locations in said expander. 
   
   
       16 . The method as set forth in  claim 8 , wherein work of expansion is utilized to assist in driving at least one component within or outside of said refrigerant system.