Insulating separators for self-defrosting evaporator coil optimized for frost-free and frost-loaded conditions

Abstract

Described herein is an evaporator and evaporator system. The system comprises a refrigerant tube formed from an electrically conductive material, the refrigerant tube being shaped to comprise a plurality of parallel tube portions; an upstream refrigerant conduit for supplying a refrigerant to the refrigerant tube; a downstream refrigerant conduit for receiving the refrigerant from the refrigerant tube; and a plurality of separators for securing the plurality of parallel tube portions in a plurality of relative positions to provide a plurality of airflow gaps separating adjacent parallel tube portions, and to impede electrical contact between different tube portions in the plurality of parallel tube portions.

1 . An evaporator comprising
 a refrigerant tube formed from an electrically conductive material, the refrigerant tube being shaped to comprise a plurality of parallel tube portions;   an upstream refrigerant conduit for supplying a refrigerant to the refrigerant tube;   a downstream refrigerant conduit for receiving the refrigerant from the refrigerant tube;   at least one current delivery connector for delivering an electrical current from an electrical current source and at least one current return connector for returning the electrical current to the electrical current source, wherein
 the at least one current delivery connector and the at least one current return connector are coupled to the refrigerant tube to provide at least one electrical flow path between the at least one current delivery connector and the at least one current return connector; 
 and 
   a plurality of separators for securing the plurality of parallel tube portions in a plurality of relative positions to provide a plurality of airflow gaps separating adjacent parallel tube portions, and to impede electrical contact between different tube portions in the plurality of parallel tube portions.   
     
     
         2 . The evaporator as defined in  claim 1 , wherein the refrigerant tube is a helically arranged refrigerant tube formed from an electrically conductive material, the refrigerant tube being curled around an axial airflow path axis to define a plurality of loops, each loop in the plurality of loops spanning a 360° rotation about a central axis, such that each point along a length of the refrigerant tube lies in a corresponding loop, and is axially positioned parallel to the central axis and radially positioned away from the central axis. 
     
     
         3 . The evaporator as defined in  claim 2 , wherein each separator in the plurality of separators is electrically insulating having a resistance greater than 100 Ω·m, to electrically insulate different segments of the refrigerant tube in contact with the separator, and wherein the separator is electrically and mechanically stable even at temperatures below −30° C. 
     
     
         4 . The evaporator as defined in  claim 3 , wherein each separator in the plurality of separators,
 has a corresponding radial dimension and an axial dimension;   intersects with at least two loops in the plurality of loops at a plurality of corresponding tube segments; and   comprises a plurality of tube engagements for engaging the refrigerant tube at, for each loop in the at least two loops, a corresponding tube segment;   wherein each corresponding tube segment is separated by at least one loop from every other corresponding tube segment in the plurality of tube segments.   
     
     
         5 . The evaporator as defined in  claim 4 , wherein each separator in the plurality of separators comprises a thickness dimension substantially orthogonal to and much smaller than the radial dimension and the axial dimension, such that that separator has a substantially planar configuration. 
     
     
         6 . The evaporator as defined in  claim 5 , wherein for each separator in the plurality of separators, the thickness dimension is between 1 mm and 20 mm. 
     
     
         7 . The evaporator as defined in  claim 5 , wherein for each separator, the thickness dimension is between 3 mm and 10 mm. 
     
     
         8 . The evaporator as defined in  claim 5 , wherein the plurality of airflow gaps comprises a plurality of radial air flow gaps, the plurality of separators block less than 10% of an airflow cross-sectional area, and the airflow cross-sectional area is one of a radial air flow cross-sectional area through the plurality of radial air flow gaps, and an axial airflow cross-sectional area of an axial airflow path parallel to the central axis. 
     
     
         9 . The evaporator as defined in  claim 5 , wherein the plurality of airflow gaps comprises a plurality of radial air flow gaps, the plurality of separators block less than 2% of an airflow cross-sectional area, and the airflow cross-sectional area is one of a radial air flow cross-sectional area through the plurality of radial air flow gaps, and an axial airflow cross-sectional area of an axial airflow path parallel to the central axis. 
     
     
         10 . The evaporator as defined in  claim 4 , wherein for each separator in the plurality of separators, the plurality of tube engagements define a gap distance for separating each loop in the at least two loops engaged by the plurality of tube engagements from a closest other loop in the at least two loops. 
     
     
         11 . The evaporator as defined in  claim 10 , wherein the gap distance varies along at least one of the axial dimension and the radial dimension. 
     
     
         12 . The evaporator as defined in  claim 4 , wherein each tube engagement in the plurality of tube engagements comprises a coupler for detachably coupling the corresponding tube segment in the plurality of tube segments, such that the separator maintains a target separation distance between the plurality of tube segments. 
     
     
         13 . A system comprising:
 the evaporator as defined in  claim 4 ; and   an air flow subsystem for providing an airflow relative to the plurality of parallel tube portions, wherein the plurality of parallel tube portions comprises an upwind layer relative to the airflow for first receiving the airflow, and at least one downwind layer relative to the airflow for subsequently receiving the airflow;   wherein the plurality of tube engagements of at least one separator in the plurality of separators includes an upwind row of tube engagements, and a downwind row of tube engagements configured such that the upwind row of tube engagements define an upwind layer gap between adjacent corresponding segments in the upwind layer, and the downwind row of tube engagements define a downwind layer gap between adjacent corresponding segments in the downwind layer, the upwind layer gap being larger than the downwind layer gap.   
     
     
         14 . The system of  claim 13 , wherein the airflow flows at least along one of the radial dimension and the axial dimension. 
     
     
         15 . The system of  claim 13 , wherein
 the plurality of separators block less than 10% of an airflow cross-sectional area through the plurality of radial airflow gaps; and   the airflow cross-sectional area is one of a radial air flow cross-sectional area through a plurality of radial air flow, and an axial airflow cross-sectional area of an axial airflow path parallel to the central axis.   
     
     
         16 . The system of  claim 13 , wherein
 the plurality of separators block less than 2% of an airflow cross-sectional area through the plurality of radial airflow gaps; and   the airflow cross-sectional area is one of a radial air flow cross-sectional area through a plurality of radial air flow, and an axial airflow cross-sectional area of an axial airflow path parallel to the central axis.   
     
     
         17 . The system of  claim 13 , wherein each separator in the plurality of separators is electrically insulating having a resistance greater than 100 Ω·m, to electrically insulate different segments of the refrigerant tube in contact with the separator, and wherein the separator is electrically and mechanically stable even at temperatures below −30° C. 
     
     
         18 . A system comprising:
 the evaporator as defined in  claim 4 ; and   an airflow subsystem for providing an airflow relative to the plurality of parallel tube portions, wherein the plurality of parallel tube portions comprises an upwind layer relative to the airflow for first receiving the airflow, and at least one downwind layer relative to the airflow for subsequently receiving the airflow;   wherein the plurality of tube engagements of each separator in the plurality of separators includes an upwind row of tube engagements, and a downwind row of tube engagements configured such that the upwind row of tube engagements define an upwind layer gap between adjacent corresponding segments in the upwind layer, and the downwind row of tube engagements define a downwind layer gap between adjacent corresponding segments in the downwind layer, the upwind layer gap being larger than the downwind layer gap.   
     
     
         19 . The system of  claim 18 , wherein the plurality of separators comprises at least three sets of separators, separated from one another by at least 80°. 
     
     
         20 . A method of configuring an evaporator coil, the method comprising:
 providing a refrigerant tube formed from an electrically conductive material, the refrigerant tube being shaped to comprise a plurality of parallel tube portions, an upstream refrigerant conduit for supplying a refrigerant to the refrigerant tube, and a downstream refrigerant conduit for receiving the refrigerant from the refrigerant tube;   providing at least one current delivery connector to the refrigerant tube for delivering an electrical current from an electrical current source and at least one current return connector for returning the electrical current to the electrical current source, the refrigerant tube providing at least one electrical flow path between the at least one current delivery connector and the at least one current return connector to generate heat to defrost the refrigerant tube during a defrost cycle;   configuring an airflow subsystem for providing an airflow relative to the plurality of parallel tube portions;   determining an air flow gap size between a parallel tube portion and a next closest parallel tube portion based at least on:
 a) the defrost cycle being less than two minutes; 
 b) maintaining a heat exchange rate of the plurality of parallel tube portions and air pressure drop between the parallel tube portion and the next closest parallel tube portion that varies linearly between a frost layer thickness of 0 mm to 25% of the gap size; and 
   configuring and providing a plurality of separators to secure the plurality of parallel tube portions in a plurality of relative positions to maintain the determined airflow gap size and to impede electrical contact between different tube portions in the plurality of parallel tube portions.