Transcritical refrigerant vapor compression system with charge management

Abstract

A refrigerant vapor compression system includes a refrigerant-to-refrigerant heat exchanger economizer and a flash tank disposed in series refrigerant flow relationship in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger. A primary expansion valve is interdisposed in the refrigerant circuit upstream of the refrigerant heat absorption heat exchanger and a secondary expansion valve is interdisposed in the refrigerant circuit upstream of the flash tank. The flash tank functions as a refrigerant charge storage reservoir wherein refrigerant expanded from a supercritical pressure to subcritical pressure separates into liquid and vapor phases. A refrigerant vapor bypass line is provided to return refrigerant vapor from the flash tank to the refrigerant circuit downstream of the refrigerant heat absorption heat exchanger. The primary expansion valve and a flow control valve interdisposed in the refrigerant vapor bypass provide refrigerant charge management.

1 . A refrigerant vapor compression system comprising:
 a primary refrigerant circuit including a refrigerant compression device, a refrigerant cooling heat exchanger for passing refrigerant received from said compression device at a high pressure in heat exchange relationship with a cooling medium, a refrigerant heating heat exchanger for passing refrigerant at a low pressure refrigerant in heat exchange relationship with a heating medium, and a primary expansion device interdisposed in the primary refrigerant circuit downstream of said refrigerant cooling heat exchanger and upstream of said refrigerant heating heat exchanger;   a refrigerant-to-refrigerant heat exchanger economizer having a first refrigerant pass disposed in the primary refrigerant circuit downstream of said refrigerant cooling heat exchanger and upstream of said primary expansion device and a second bypass disposed in an economizer circuit refrigerant line;   a flash tank disposed in the primary refrigerant circuit downstream of the first refrigerant pass of said refrigerant-to-refrigerant exchanger and upstream of said primary expansion device, said flash tank defining a separation chamber wherein refrigerant in a liquid state collects in a lower portion of said separation chamber and refrigerant in a vapor state in a portion of said separation chamber above the liquid refrigerant;   a secondary expansion device disposed in the primary refrigerant circuit in operative association with and upstream with of said flash tank;   an refrigerant vapor bypass line establishing refrigerant flow communication between an upper portion of said separation chamber of said flask tank and a suction pressure portion of said primary refrigerant circuit downstream of said refrigerant heat absorption heat exchanger; and   a bypass flow control valve interdisposed in said evaporator bypass line, said bypass flow control valve having a first open position whereat refrigerant vapor may pass through said evaporator bypass line and a second closed position whereat refrigerant vapor is blocked from passing through said evaporator bypass line.   
   
   
       2 . A refrigerant vapor compression system as recited in  claim 1  wherein said flow control valve comprises a solenoid valve having a first open position and a second closed position. 
   
   
       3 . A refrigerant vapor compression system as recited in  claim 1  wherein said flow control valve comprises a pulse width modulated solenoid valve. 
   
   
       4 . A refrigerant vapor compression system as recited in  claim 1  wherein said flow control valve comprises an electronic expansion valve. 
   
   
       5 . A refrigerant vapor compression system as recited in  claim 1  wherein said primary expansion device comprises an electronic expansion valve. 
   
   
       6 . A refrigerant vapor compression system as recited in  claim 1  wherein said primary expansion device comprises a thermostatic expansion valve. 
   
   
       7 . A refrigerant vapor compression system as recited in  claim 1  wherein said secondary expansion device comprises an electronic expansion valve. 
   
   
       8 . A refrigerant vapor compression system as recited in  claim 1  wherein said secondary expansion device comprises a fixed orifice expansion device. 
   
   
       9 . A refrigerant vapor compression system as recited in  claim 1  wherein said economizer circuit refrigerant line extends in refrigerant flow communication from said primary refrigerant circuit to an intermediate pressure stage of said compression device. 
   
   
       10 . A refrigerant vapor compression system as recited in  claim 9  further comprising an economizer circuit expansion device interdisposed in said economizer circuit refrigerant line upstream with respect to refrigerant flow of the second refrigerant pass of said refrigerant-to-refrigerant heat exchanger economizer. 
   
   
       11 . A refrigerant vapor compression system as recited in  claim 10  wherein said economizer circuit expansion device comprises an electronic expansion valve. 
   
   
       12 . A refrigerant vapor compression system as recited in  claim 10  wherein said economizer circuit expansion device comprises a thermostatic expansion valve. 
   
   
       13 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises a single compressor having at least two compression stages. 
   
   
       14 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises at least two compressors disposed in the refrigerant circuit in a series relationship with respect to refrigerant flow. 
   
   
       15 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises a scroll compressor. 
   
   
       16 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises a reciprocating compressor. 
   
   
       17 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises a screw compressor. 
   
   
       18 . A refrigerant vapor compression system as recited in  claim 1  wherein said system is incorporated in a transport refrigeration system for conditioning a temperature controlled cargo storage region. 
   
   
       19 . A refrigerant vapor compression system as recited in  claim 18  wherein said system operates in a transcritical cycle. 
   
   
       20 . A refrigerant vapor compression system as recited in  claim 19  wherein the refrigerant comprises carbon dioxide.