Liquid vapor separation in transcritical refrigerant cycle

Abstract

A refrigerant vapor compression system includes a flash tank disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger. The flash tank has a shell defining an interior volume having an upper chamber, a lower chamber and a middle chamber. A first fluid passage establishes fluid communication between the middle chamber and the upper chamber and a second fluid passage establishing fluid communication between the middle chamber and the lower chamber. An inlet port opens to the middle chamber. A first outlet port opens to the upper chamber and a second outlet port opens to the lower chamber.

1 . A transport refrigeration refrigerant vapor compression system operating in a transcritical refrigeration cycle comprising:
 a compression device for compressing a refrigerant vapor to a supercritical refrigerant pressure, a gas cooler operating at a supercritical refrigerant pressure, and an evaporator operating at a subcritical refrigerant pressure, said compression device, said gas cooler and said evaporator connected in refrigerant flow communication in a refrigerant circuit;   a primary expansion device disposed in said refrigerant circuit between said gas cooler and said evaporator;   a secondary expansion device disposed in said refrigerant circuit between said gas cooler and said primary expansion device;   a flash tank disposed in the refrigerant circuit upstream with respect to refrigerant flow of said primary expansion device and downstream with respect to refrigerant flow of said secondary expansion device, said flash tank having:   a shell defining an interior volume, said interior volume divided into an upper chamber, a lower chamber and a middle chamber;   a first fluid passage establishing fluid communication between the middle chamber and the upper chamber;   a second fluid passage establishing fluid communication between the middle chamber and the lower chamber;   an inlet port in fluid communication with the middle chamber for receiving the refrigerant flow having traversed the secondary expansion device;   a first outlet port in fluid communication with the upper chamber for discharging a vapor phase of the refrigerant flow from said flash tank separator; and   a second outlet port in fluid communication with the lower chamber for discharging a liquid phase of the refrigerant flow from said flash tank into the refrigerant circuit.   
     
     
         2 . The transport refrigeration refrigerant vapor compression system as recited in  claim 1  further comprising: a refrigerant vapor injection line establishing refrigerant flow communication between the first outlet port in fluid communication with the upper chamber of said flask tank and an intermediate pressure stage of said compression device. 
     
     
         3 . The transport refrigeration refrigerant vapor compression system as recited in  claim 1  further comprising: a refrigerant liquid injection line establishing refrigerant flow communication between the second outlet port in fluid communication with the lower chamber of said flash tank and an intermediate pressure stage of said compression device. 
     
     
         4 . The transport refrigerant vapor compression system as recited in  claim 1  wherein said flash tank further comprises:
 a lower plate and an upper plate disposed in spaced relationship within the interior volume defined by said shell, each of said lower plate and said upper plate extending across the interior volume thereby sectioning the interior volume into the lower chamber, the middle chamber and the lower chamber; 
 a first opening extending through said upper plate and forming the first fluid passage establishing fluid communication between said middle chamber and said upper chamber; and 
 a second opening extending through said lower plate and forming the second fluid passage establishing fluid communication between said middle chamber and said lower chamber. 
 
     
     
         5 . The transport refrigerant vapor compression system as recited in  claim 1  wherein said flash tank further comprises:
 an elongated support tube extending along a central vertical axis of said shell, said support tube defining a conduit establishing fluid communication between said lower chamber and said upper chamber; and 
 a helical spiral member extending about said vertical support tube and defining a continuous spiral fluid flow passage, a first portion of said continuous helical passage forming the first fluid passage establishing fluid communication between the middle chamber and the upper chamber and a second portion of said continuous helical passage forming the second fluid passage establishing fluid communication between the middle chamber and the lower chamber. 
 
     
     
         6 . A refrigerant vapor compression system as recited in  claim 1  wherein the refrigerant comprises carbon dioxide. 
     
     
         7 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises a single compressor having at least a first relatively lower pressure compression stage and a second relatively higher pressure compression stage. 
     
     
         8 . A refrigerant vapor compression system as recited in  claim 1  wherein said compression device comprises a first compressor and a second compressor disposed in said refrigerant circuit in series refrigerant flow relationship with a discharge outlet of said first compressor in refrigerant flow communication with a suction inlet of said second compressor. 
     
     
         9 . A refrigerant vapor compression system as recited in  claim 5  further comprising:
 an upper equalization hole passing through said support tube and located near an upper end of said support tube, said upper equalization hole establishing fluid communication between an upper region of said conduit and an upper region of said continuous helical passage; and 
 a lower equalization hole passing through said support tube and located near a lower end of said support tube, said lower equalization hole establishing fluid communication between a lower region of said conduit and a lower region of said continuous helical passage. 
 
     
     
         10 . A flash tank separator comprising:
 a shell defining an interior volume;   a lower plate and an upper plate disposed in spaced relationship within the interior volume defined by said shell, each of said lower plate and said upper plate extending across the interior volume thereby sectioning the interior volume into the lower chamber, the middle chamber and the lower chamber;   a first opening extending through said upper plate and establishing fluid communication between said middle chamber and said upper chamber;   a second opening extending through said lower plate and establishing fluid communication between said middle chamber and said lower chamber;   an inlet port in fluid communication with the middle chamber for receiving a flow of a mixed liquid phase and vapor phase fluid;   a first outlet port in fluid communication with the upper chamber for discharging a vapor phase of the refrigerant flow from the upper chamber; and   a second outlet port in fluid communication with the lower chamber for discharging a liquid phase from the lower chamber.   
     
     
         11 . The flash tank separator as recited in  claim 10  wherein the first opening in said upper plate and the second opening in said lower plate are disposed remotely from each other. 
     
     
         12 . The flash tank separator as recited in  claim 10  further comprising an inlet tube penetrating said shell and having a fluted outlet defining said inlet port. 
     
     
         13 . A flash tank separator comprising:
 a shell defining an interior volume having an upper chamber, a middle chamber and a lower chamber;   an elongated support tube extending along a central vertical axis of said shell between the lower chamber and the upper chamber;   a helical spiral member extending about said vertical support tube and defining a continuous spiral fluid flow passage, a first portion of said continuous helical passage establishing fluid communication between the middle chamber and the upper chamber and a second portion of said continuous helical passage establishing fluid communication between the middle chamber and the lower chamber;   an upper equalization hole passing through said support tube and located near an upper end of said support tube, said upper equalization hole establishing fluid communication between an upper region of said conduit and an upper region of said continuous helical passage;   a lower equalization hole passing through said support tube and located near a lower end of said support tube, said lower equalization hole establishing fluid communication between a lower region of said conduit and a lower region of said continuous helical passage;   an inlet port in fluid communication with the middle chamber for receiving the refrigerant flow having traversed the secondary expansion device;   a first outlet port in fluid communication with the upper chamber for discharging a gas phase of the refrigerant flow from said flash tank separator; and   a second outlet port in fluid communication with the lower chamber for discharging a liquid phase of the refrigerant flow from said flash tank into the refrigerant circuit.   
     
     
         14 . The flash tank separator as recited in  claim 13  further comprising an inlet tube penetrating said shell and having a outlet defining said inlet port for directing an incoming flow of a mixed liquid phase and vapor phase fluid to pass circumferentially along an inner wall of said shell.