Defrost system and method of defrosting an evaporator section of a temperature control unit

Abstract

A defrost system for a temperature control unit includes an evaporator section having a refrigerant inlet ( 54 ) and a refrigerant outlet. Also disclosed is a first heating element ( 80 ). Further disclosed is a second heating element ( 82 ), the first heating element ( 80 ) located closer to the refrigerant inlet ( 54 ) than the second heating element ( 82 ) is to the refrigerant inlet ( 54 ). Yet further disclosed is a first sensing device ( 60 ) for detecting ice buildup at the refrigerant inlet ( 54 ), wherein heating activation of the first heating element ( 80 ) is determined at least in part by ice buildup detection of the first sensing device ( 60 ). Also disclosed is a second sensing device ( 70 ) for detecting ice buildup along the second heating element ( 82 ), wherein heating activation of the second heating element ( 82 ) is determined at least in part by ice buildup detection of the second sensing device ( 70 ).

What is claimed is: 
     
         1 . A defrost system for a temperature control unit comprising:
 an evaporator section having a refrigerant inlet and a refrigerant outlet;   a first heating element;   a second heating element, the first heating element located closer to the refrigerant inlet than the second heating element is to the refrigerant inlet;   a first sensing device for detecting ice buildup at the refrigerant inlet, wherein heating activation of the first heating element is determined at least in part by ice buildup detection of the first sensing device; and   a second sensing device for detecting ice buildup along the second heating element, wherein heating activation of the second heating element is determined at least in part by ice buildup detection of the second sensing device.   
     
     
         2 . The defrost system of  claim 1 , wherein at least one of the first sensing device and the second sensing device is an air switch for detecting a pressure differential. 
     
     
         3 . The defrost system of  claim 1 , wherein the first heating element and the second heating element are each electric heating elements. 
     
     
         4 . The defrost system of  claim 1 , wherein the first heating element and the second heating element are oriented perpendicular to each other. 
     
     
         5 . The defrost system of  claim 1 , wherein the first heating element is oriented vertically relative to the evaporator section, the second heating element oriented along a longitudinal direction of the evaporator section. 
     
     
         6 . The defrost system of  claim 1 , wherein the first heating element may be activated during cooling system operation of the temperature control unit. 
     
     
         7 . The defrost system of  claim 1 , wherein the first heating element is one of a plurality of first heating elements and the second heating element is one of a plurality of second heating elements, each of the first heating elements located closer to the refrigerant inlet than each of the plurality of second heating elements is to the refrigerant inlet. 
     
     
         8 . The defrost system of  claim 1 , wherein the temperature control unit is a transport refrigeration unit. 
     
     
         9 . The defrost system of  claim 1 , wherein the first sensing device and the second sensing device are each temperature sensors for detecting a temperature differential. 
     
     
         10 . A method of defrosting an evaporator section of a temperature control unit comprising:
 detecting the presence of ice buildup at a first location proximate a refrigerant inlet of the evaporator section with a first sensing device;   detecting the presence of ice buildup at a second location of the evaporator section with a second sensing device;   activating a first heating element upon detection of the presence of ice buildup at the first location; and   activating a second heating element upon detection of the presence of ice buildup at the second location.   
     
     
         11 . The method of  claim 10 , further comprising separately controlling the first heating element and the second heating element. 
     
     
         12 . The method of  claim 10 , further comprising activating the first heating element without activating the second heating element. 
     
     
         13 . The method of  claim 12 , further comprising activating the first heating element during cooling system operation of the temperature control unit. 
     
     
         14 . The method of  claim 10 , wherein detecting the presence of ice buildup at the first location and the second location comprises detecting a first pressure differential at the first location and detecting a first pressure differential at the second location. 
     
     
         15 . The method of  claim 10 , further comprising orienting the first heating element and the second heating element perpendicular to each other. 
     
     
         16 . The method of  claim 10 , further comprising orienting the first heating element vertically relative to the evaporator section, and orienting the second heating element along a longitudinal direction of the evaporator section.