Dynamic superheat control for high efficiency refrigeration system

Abstract

A vapor compression refrigeration system including components capable of determining the superheat at a compressor inlet is provided. The vapor compression refrigeration system may include sensors capable of making measurements from which the superheat at the compressor inlet may be determined. The vapor compression refrigeration system may be operable to compare the determined superheat level at the inlet to the compressor to a desired superheat level and generate a new evaporator discharge superheat level target for one or more evaporators operatively interconnected to the compressor to affect the superheat at the compressor inlet. The vapor compression refrigeration system may be operable to broadcast the new evaporator discharge superheat level target to the one or more evaporators over a communications bus. The vapor compression refrigeration system may update and broadcast the evaporator discharge superheat level target at programmed intervals.

1 . A method of operating a vapor compression refrigeration system, said method comprising:
 determining a level of superheat at the inlet to a compressor of said vapor compression refrigeration system;   comparing said determined level of superheat at the inlet to said compressor to a compressor inlet superheat target;   calculating a revised evaporator superheat target at least partially based on said comparing step; and   adjusting an output level of superheat of an evaporator of said vapor compression refrigeration system based on said revised evaporator superheat target by adjusting an expansion valve associated with said evaporator.   
     
     
         2 . The method of  claim 1 , wherein said comparing step further comprises calculating a difference between said determined level of superheat at the inlet to said compressor and said compressor inlet superheat target, wherein said revised evaporator superheat target is at least partially based on a previous evaporator superheat target and said difference. 
     
     
         3 . The method of  claim 2 , wherein said compressor inlet superheat level is maintained within a two degree F. window. 
     
     
         4 . The method of  claim 1 , further comprising performing said adjusting step for a plurality of evaporators, wherein each evaporator has an associated expansion valve, a fan, and an electronic evaporator controller. 
     
     
         5 . The method of  claim 4 , further comprising broadcasting said revised evaporator superheat target to said plurality of electronic evaporator controllers. 
     
     
         6 . The method of  claim 5 , wherein said comparing, calculating and broadcasting steps are performed by an electronic compressor controller. 
     
     
         7 . The method of  claim 4 , further comprising varying a capacity of said compressor. 
     
     
         8 . The method of  claim 4 , further comprising varying a discharge pressure of said compressor. 
     
     
         9 . The method of  claim 4 , further comprising varying a speed of at least one of said plurality of fans. 
     
     
         10 . The method of  claim 1 , further comprising sending said revised evaporator superheat target to an evaporator controller. 
     
     
         11 . The method of  claim 10 , wherein said adjusting step is performed by an electronic evaporator controller. 
     
     
         12 . The method of  claim 10 , wherein said comparing, calculating and sending steps are performed by an electronic compressor controller. 
     
     
         13 . The method of  claim 1 , further comprising repeating said determining, comparing, calculating, and adjusting steps a plurality of times during a day to compensate for variations in ambient conditions during said day. 
     
     
         14 . A method of operating a vapor compression refrigeration system, said method comprising:
 determining a compressor inlet superheat level at an inlet to a compressor of said vapor compression refrigeration system;   monitoring for a first condition, said first condition being said compressor inlet superheat level being out of compliance with a compressor inlet superheat target;   sending a signal upon each occurrence of said first condition; and   adjusting an evaporator output superheat level at an output to an evaporator of said vapor compression refrigeration system in response to each execution of said sending step.   
     
     
         15 . The method of  claim 14 , wherein said sending step comprises broadcasting a revised evaporator superheat target to a plurality of evaporator controllers. 
     
     
         16 . The method of  claim 14 , further comprising adjusting an evaporator output superheat level at each output of a plurality of evaporators of said vapor compression refrigeration system in response to each execution of said sending step. 
     
     
         17 . The method of  claim 14 , further comprising repeating said determining, monitoring, sending and adjusting steps a plurality of times during a day and in an automated fashion.