Hot Gas Defrost Using a Work Recovery Device

Abstract

A refrigeration system comprises a gas cooler, a flash tank, a work recovery device located downstream from the gas cooler, one or more evaporators unit located downstream from a second outlet of the work recovery device, and a controller communicatively coupled to the work recovery device.

What is claimed is: 
     
         1 . A refrigeration system, comprising a gas cooler, a flash tank, a work recovery device located downstream from the gas cooler, and a controller communicatively coupled to the work recovery device, wherein:
 the flash tank is configured to store refrigerant;   the gas cooler is configured to receive the refrigerant and facilitate heat transfer from the received refrigerant, thereby cooling the refrigerant;   the controller is configured to:
 turn on the work recovery device; 
 cause the work recovery device, while turned on, to:
 receive, at a first inlet, a flow of refrigerant cooled by the gas cooler; 
 reduce a pressure of the first flow of refrigerant; 
 provide, from a first outlet, the first flow of refrigerant to the flash tank; 
 
   wherein the work recovery device comprises one of a turbine, a rotating device, an expander, a scroll expander, or a reciprocating piston expander.   
     
     
         2 . The refrigeration system of  claim 1 , further comprising a refrigerant conduit configured to allow the flow of refrigerant from the gas cooler to the work recovery device, wherein the flow of refrigerant from the gas cooler comprises vapor refrigerant. 
     
     
         3 . The refrigeration system of  claim 1 , wherein the refrigerant provided to the gas cooler is supplied from at least one of a first evaporator unit or a second evaporator unit operating in the refrigeration mode. 
     
     
         4 . The refrigeration system of  claim 1 , wherein the controller is further configured to turn off the work recovery device. 
     
     
         5 . The refrigeration system of  claim 1 , wherein the controller is further configured to at least partially open a first valve to allow the flow of refrigerant from the gas cooler to the work recovery device. 
     
     
         6 . The refrigeration system of  claim 5 , wherein the controller is further configured to at least partially close the first valve to prevent the flow of refrigerant from the gas cooler to the work recovery device. 
     
     
         7 . The refrigeration system of  claim 5 , wherein the controller is further configured to at least partially open a second valve to allow flow of refrigerant from an oil separator to a first evaporator unit. 
     
     
         8 . The refrigeration system of  claim 1 , wherein the controller is further configured to at least partially close a valve to prevent flow of refrigerant from an oil separator to a first evaporator unit. 
     
     
         9 . A method of operating a refrigeration system, the method comprising:
 turning on a work recovery device;   causing the work recovery device, while turned on, to:
 receive, at a first inlet, a flow of refrigerant cooled by a gas cooler; 
 reduce a pressure of the first flow of refrigerant; and 
 provide, from a first outlet, the first flow of refrigerant to a flash tank; 
 wherein the work recovery device comprises one of a turbine, a rotating device, an expander, a scroll expander, or a reciprocating piston expander. 
   
     
     
         10 . The method of  claim 9 , further comprising causing the flow of the refrigerant from the gas cooler to the work recovery device, wherein the refrigerant from the gas cooler comprises vapor refrigerant. 
     
     
         11 . The method of  claim 9 , wherein the refrigerant provided to the gas cooler is supplied from at least one of a first evaporator unit or a second evaporator unit operating in the refrigeration mode. 
     
     
         12 . The method of  claim 9 , further comprising turning off the work recovery device. 
     
     
         13 . The method of  claim 9 , further comprising at least partially opening a first valve to allow the flow of refrigerant from the gas cooler to the work recovery device. 
     
     
         14 . The method of  claim 13 , further comprising at least partially closing the first valve to prevent the flow of refrigerant from the gas cooler to the work recovery device. 
     
     
         15 . The method of  claim 13 , further comprising at least partially opening a second valve to allow flow of refrigerant from an oil separator to a first evaporator unit. 
     
     
         16 . The method of  claim 9 , further comprising at least partially closing a valve to prevent flow of refrigerant from an oil separator to the a evaporator unit.