High performance refrigerator having insulated evaporator cover

Abstract

A high performance refrigerator includes a cabinet with a refrigerated interior, an insulating cover separating a portion of the cabinet from the refrigerated interior, and a refrigeration fluid circuit having an evaporator located within the portion of the cabinet separated by the insulating cover from the refrigerated interior. The refrigerator also includes a controller that commands the refrigerator to perform a defrosting cycle when the evaporator coil requires defrosting. This defrosting cycle includes closing dampers in the insulating cover during the defrosting of the evaporator coil, thereby keeping the refrigerated interior thermally isolated from the evaporator during the defrost cycle. The controller is also operable to stop operation of a defrost heater when the evaporator reaches a first target temperature above the freezing point of water, and to re-open the dampers when the evaporator reaches a second target temperature above the freezing point of water.

What is claimed is: 
     
         1 . A refrigerator, comprising:
 a cabinet having a refrigerated interior;   a refrigeration fluid circuit for circulating a refrigerant, the refrigeration fluid circuit including a compressor, a condenser, an expansion device, and an evaporator located within the cabinet and including an evaporator coil, an evaporator fan producing air flow through the evaporator coil, and a defrost heater;   an insulating cover separating a portion of the cabinet containing the evaporator from the refrigerated interior, the insulating cover including at least one damper that may open to permit air circulation from the refrigerated interior through the evaporator; and   a controller operable to command the refrigerator to perform the following steps when the evaporator coil requires defrosting:
 stop operation of the compressor and the evaporator fan; 
 close the at least one damper to thermally isolate the evaporator from the refrigerated interior; and 
 start operation of the defrost heater, 
 wherein the refrigerated interior remains thermally isolated from the evaporator during operation of the defrost heater. 
   
     
     
         2 . The refrigerator of  claim 1 , further comprising a temperature sensor for detecting the temperature of the evaporator, and wherein the controller is further operable to command the refrigerator to perform the following steps during defrosting of the evaporator:
 when the temperature sensor detects that the evaporator has reached a first target temperature above the freezing point of water, stopping operation of the defrost heater and allowing for any remaining moisture to drip off the evaporator coils;   starting the compressor after the remaining moisture drips off the evaporator coils; and   when the temperature sensor detects that the evaporator has reached a second target temperature below the freezing point of water, opening the at least one damper and starting operation of the evaporator fan.   
     
     
         3 . The refrigerator of  claim 2 , wherein the first target temperature is about 10° C. and the second target temperature is about −25° C. 
     
     
         4 . The refrigerator of  claim 1 , wherein the at least one damper includes a first damper and a second damper, the first damper in an open position permitting air flow into the evaporator from the refrigerated interior, the second damper in an open position permitting air flow from the evaporator into the refrigerated interior. 
     
     
         5 . The refrigerator of  claim 1 , wherein the insulated cover further includes a plurality of insulated panels that collectively divide the cabinet into an evaporator chamber and the refrigerated interior when the at least one damper is closed. 
     
     
         6 . The refrigerator of  claim 5 , wherein each of the insulated panels is a vacuum insulated panel. 
     
     
         7 . The refrigerator of  claim 1 , wherein the expansion device includes at least one of a capillary tube or a valve. 
     
     
         8 . The refrigerator of  claim 1 , wherein the refrigeration fluid circuit further includes an accumulator operatively connected to the evaporator and the compressor. 
     
     
         9 . The refrigerator of  claim 1 , wherein the refrigeration fluid circuit further includes a filter/dryer operatively connected to the condenser and the expansion device. 
     
     
         10 . The refrigerator of  claim 1 , wherein the controller is operable to modify an amount of time between defrost cycles and to modify an amount of time the defrost heater is operating during a defrost cycle based on at least one measurable operating parameter. 
     
     
         11 . A method of operating a refrigerator including a cabinet having a refrigerated interior, a refrigeration fluid circuit including a compressor, a condenser, and an evaporator located within the cabinet and having an evaporator fan and defrost heater, the refrigerator further including an insulating cover with at least one damper configured to separate the evaporator from the refrigerated interior of the cabinet, and the method comprises:
 stopping operation of the compressor and the evaporator fan;   closing the at least one damper to thermally isolate the evaporator from the refrigerated interior; and   starting operation of the defrost heater,   wherein the refrigerated interior remains thermally isolated from the evaporator during operation of the defrost heater.   
     
     
         12 . The method of  claim 11 , further comprising:
 when the evaporator has reached a first target temperature above the freezing point of water, stopping operation of the defrost heater and allowing for any remaining moisture to drip off the evaporator coils;   starting the compressor after the remaining moisture drips off the evaporator coils; and   when the evaporator has reached a second target temperature below the freezing point of water, opening the at least one damper and starting operation of the evaporator fan.   
     
     
         13 . The method of  claim 12 , wherein the first target temperature is about 10° C. and the second target temperature is about −25° C. 
     
     
         14 . The method of  claim 11 , wherein the at least one damper includes a first damper and a second damper, the first damper in an open position permitting air flow into the evaporator from the refrigerated interior, the second damper in an open position permitting air flow from the evaporator into the refrigerated interior, and the first and second dampers are simultaneously closed by the refrigerator when the operation of the evaporator fan is stopped. 
     
     
         15 . A method of operating a refrigerator including a cabinet having a refrigerated interior, a refrigeration fluid circuit including a compressor, a condenser, and an evaporator located within the cabinet and having an evaporator fan and defrost heater, the refrigerator further including an insulating cover with at least one damper configured to separate the evaporator from the refrigerated interior of the cabinet, and the method comprises:
 starting the operation of the defrost heater when the at least one damper is closed; and   when the evaporator has reached a first target temperature above the freezing point of water, stopping operation of the defrost heater and starting operation of the compressor; and   when the evaporator has reached a second target temperature below the freezing point of water, opening the at least one damper and starting operation of the evaporator fan.   
     
     
         16 . The method of  claim 15 , wherein the first target temperature is about 10° C. and the second target temperature is about −25° C. 
     
     
         17 . The method of  claim 15 , wherein the at least one damper includes a first damper and a second damper, the first damper in an open position permitting air flow into the evaporator from the refrigerated interior, the second damper in an open position permitting air flow from the evaporator into the refrigerated interior, and the first and second dampers are simultaneously opened by the refrigerator when the operation of the evaporator fan is started.