Refrigerant injection above critical point in a transcritical refrigerant system

Abstract

A refrigerant system operates in a transcritical regime. An economizer circuit is incorporated into the refrigerant system, and includes an economizer injection line for refrigerant injection above the critical point. In one of the disclosed embodiments, the refrigerant utilized is CO 2 .

1 . A refrigerant system comprising:
 a compressor for compressing refrigerant and delivering it downstream to a heat rejection heat exchanger, the refrigerant from said heat rejection heat exchanger passing through a main expansion device, and then to a heat accepting heat exchanger, before being returned to said compressor;   an injection line injecting a portion of a refrigerant tapped downstream of the heat rejection heat exchanger back into the compressor at an injection point; and   
     said compressor compressing a refrigerant through a transcritical cycle, where the injection may occur, for at least a portion of the time, above a critical point. 
   
   
       2 . The refrigerant system as set forth in  claim 1 , wherein an economizer circuit is incorporated between the heat rejection heat exchanger and the main expansion device, said economizer circuit including at least an economizer and an economizer expansion device, receiving a main refrigerant flow from the heat rejection heat exchanger and delivering it downstream through the main expansion device, tapping a portion of the refrigerant flow upstream of said main expansion device into the injection line and injecting the tapped refrigerant into said compressor at the injection point. 
   
   
       3 . The refrigerant system as set forth in  claim 2 , wherein the economizer circuit is a pair of economizer circuits having a pair of economizers, with an upstream economizer and a downstream economizer, and a pair of associated refrigerant injection points into the compression process, with an upstream refrigerant injection point and a downstream refrigerant injection point. 
   
   
       4 . The refrigerant system as set forth in  claim 3 , wherein said compressor includes a two-stage compressor. 
   
   
       5 . The refrigerant system as set forth in  claim 3 , wherein one of said two economizer circuits delivers the tapped refrigerant back to the compressor a point above the critical point, and the other of the two economizer circuits delivers a refrigerant back to the compressor at a point below the critical point. 
   
   
       6 . The refrigerant system as set forth in  claim 5 , wherein the economizer circuit that delivers the refrigerant to a point below the critical point, delivers the refrigerant to a point intermediate the two compression stages. 
   
   
       7 . The refrigerant system as set forth in  claim 5 , wherein the economizer circuit that delivers the refrigerant back to the compressor at a point below the critical point is a downstream economizer circuit, and the economizer circuit that delivers the refrigerant back to the compressor at a point above the critical point is an upstream economizer circuit. 
   
   
       8 . The refrigerant system as set forth in  claim 2 , wherein said economizer is a heat exchanger type economizer. 
   
   
       9 . The refrigerant system as set forth in  claim 8 , wherein said tapped portion of refrigerant flow is tapped at a location upstream of the economizer and downstream of the heat rejection heat exchanger. 
   
   
       10 . The refrigerant system as set forth in  claim 8 , wherein said tapped portion of refrigerant flow is tapped at a location downstream of the economizer and upstream of the main expansion device. 
   
   
       11 . The refrigerant system as set forth in  claim 2 , wherein said economizer is a flash tank type economizer. 
   
   
       12 . The refrigerant system as set forth in  claim 2 , wherein a second portion of refrigerant is tapped downstream of heat rejection heat exchanger, expanded and injected back into the compressor, without passing through the economizer. 
   
   
       13 . The refrigerant system as set forth in  claim 12 , wherein the two tapped refrigerant flows are injected into the compression process at the same injection point. 
   
   
       14 . The refrigerant system as set forth in  claim 12 , wherein the two tapped refrigerant flows are injected into the compression process at different injection points. 
   
   
       15 . The refrigerant system as set forth in  claim 14 , wherein the injection point for the tapped refrigerant flow that does not pass through the economizer is upstream of the injection point of the refrigerant that has passed through the economizer. 
   
   
       16 . The refrigerant system as set forth in  claim 14 , wherein the injection point for the tapped refrigerant flow that does not pass through the economizer is downstream of the injection point of the refrigerant that has passed through the economizer. 
   
   
       17 . The refrigerant system as set forth in  claim 1 , wherein said compressor is a two-stage compressor. 
   
   
       18 . The refrigerant system as set forth in  claim 1 , wherein said compressor is a pair of separate compressors. 
   
   
       19 . The refrigerant system as set forth in  claim 1 , wherein the refrigerant utilized in the refrigerant system is CO2. 
   
   
       20 . The refrigerant system as set forth in  claim 1 , wherein said tapped portion of the refrigerant is expanded and directly injected back into the compressor at said injection point, without passing through an economizer. 
   
   
       21 - 40 . (canceled)