An evaporator assembly

Abstract

An evaporator assembly comprises at least one plate evaporator, each plate evaporator comprising first and second sheets that are joined together and that define an internal conduit between the sheets. The internal conduit is aligned parallel to the sheets and is configured to carry refrigerant through the plate evaporator, each plate evaporator further comprising a first electrically insulative layer applied on the first sheet, an electrically resistive layer applied on the first electrically insulative layer, and a second electrically insulative layer applied on the electrically resistive layer. The electrically resistive layer is an elongated track that follows a meandering path traversing along the first sheet.

What is claimed is: 
     
         1 . An evaporator assembly comprising at least one plate evaporator, each plate evaporator comprising first and second sheets that are joined together and that define an internal conduit between the sheets, the internal conduit aligned parallel to the sheets and configured to carry refrigerant through the plate evaporator, each plate evaporator further comprising a first electrically insulative layer applied on the first sheet, an electrically resistive layer applied on the first electrically insulative layer, and a second electrically insulative layer applied on the electrically resistive layer, wherein the electrically resistive layer is an elongated track that follows a meandering path traversing along the first sheet. 
     
     
         2 . The evaporator assembly of  claim 1 , wherein the first electrically insulative layer is also an elongated track that follows the meandering path, between the first sheet and the electrically insulative layer. 
     
     
         3 . The evaporator assembly of  claim 1 , wherein the second electrically insulative layer extends over and encapsulates both the first and the second sheets. 
     
     
         4 . The evaporator assembly of  claim 1 , wherein the internal conduit follows at least a portion of the meandering path. 
     
     
         5 . The evaporator assembly of  claim 1 , wherein the first electrically insulative layer adheres to the first sheet, and wherein the electrically resistive layer adheres to the first electrically insulative layer. 
     
     
         6 . The evaporator assembly of  claim 5 , wherein the first electrically insulative layer is a paint layer that is painted on the first sheet. 
     
     
         7 . The evaporator assembly of  claim 5 , wherein the electrically resistive layer is a paint layer that is painted on the first electrically insulative layer. 
     
     
         8 . The evaporator assembly of  claim 7 , wherein the paint of the electrically resistive layer comprises a nickel-chromium powder. 
     
     
         9 . The evaporator assembly of  claim 1 , wherein the second electrically insulative layer forms an exterior surface of the plate evaporator. 
     
     
         10 . The evaporator assembly of  claim 1 , wherein the second electrically insulative layer is applied directly to the second sheet without any first insulative layer or electrically resistive layer between the second electrically insulative layer and the second sheet. 
     
     
         11 . The evaporator assembly of  claim 1 , wherein the first and second sheets are metal sheets. 
     
     
         12 . The evaporator assembly of  claim 1 , comprising a heater control unit that is electrically connected to opposing ends of the elongated track of the electrically resistive layer, and configured to drive an electric current along the elongated track of the electrically resistive layer to heat the plate evaporator in a defrost mode. 
     
     
         13 . The evaporator assembly of  claim 12 , wherein the heater control unit is configured to receive a signal indicating when the flow of refrigerant through the plate evaporator has ceased, and to only enter the defrost mode of the plate evaporator when the signal indicates the flow of refrigerant through the plate evaporator has ceased. 
     
     
         14 . The evaporator assembly of  claim 1 , comprising a plurality of the plate evaporators arranged parallel to one another, and further comprising an inlet manifold for connecting to a compressor, an outlet manifold for connecting to a condenser, and pipes connecting the internal conduits of the plate evaporators to the inlet and outlet manifolds. 
     
     
         15 . The evaporator assembly of  claim 14 , comprising a heater control unit that is electrically connected to opposing ends of the elongated track of the electrically resistive layer of each plate evaporator, and configured to drive an electric current along the elongated track of the electrically resistive layer to heat the plate evaporator in a defrost mode, wherein the heater control unit is configured to drive an electric current through the elongated tracks of the plate evaporators in sequence such that the plate evaporators are not all in the defrost mode at a same time as one another. 
     
     
         16 . The evaporator assembly of  claim 15 , wherein the heater control unit is configured to receive a signal indicating when the flow of refrigerant through the plate evaporators has ceased, and to only enter the defrost mode of each plate evaporator when the signal indicates the flow of refrigerant through the plate evaporator has ceased, wherein the heater control unit is configured to enter the defrost mode of at least one of the plate evaporators every time that the signal is received indicating the flow of refrigerant has ceased. 
     
     
         17 . The evaporator assembly of  claim 15 , wherein the heater control unit is configured to enter the defrost mode of only one plate evaporator at a time. 
     
     
         18 . The evaporator assembly of  claim 16 , wherein the plate evaporators are arranged with the first sheet and the second sheet of immediately adjacent plate evaporators facing towards one another. 
     
     
         19 . An evaporator system comprising at least one plate evaporator, each plate evaporator comprising first and second sheets that are joined together and that define an internal conduit between the sheets, the internal conduit aligned parallel to the sheets and configured to carry refrigerant through the plate evaporator, each plate evaporator further comprising a first electrically insulative layer applied on the first sheet, an electrically resistive layer applied on the first electrically insulative layer, and a second electrically insulative layer applied on the electrically resistive layer, wherein the electrically resistive layer is an elongated track that follows a meandering path traversing along the first sheet. 
     
     
         20 . The system of  claim 19  including a temperature sensing element configured to sense temperature within a refrigeration space to be refrigerated by the at least one plate evaporator, and a controller configured to control the flow of refrigerant through the at least one plate evaporator based on the temperature sensing element, wherein the temperature sensing element comprises a food simulant material and a temperature probe embedded within the food simulant material, wherein the food simulant material is preferably a solid wax in which are distributed a plurality of gas-filled polymeric particles.