Impedance Heating for Heat Exchanger Water Drainage Channels

Abstract

Embodiments of the invention provide anti-icing systems ( 201 ) for drainage channels ( 203; 205 ) used to remove water run-off during heat pump evaporator coil defrosting cycles during cold weather conditions. The invention employs impedance heating to obviate heat tracing cable, its associated thermal insulation and any protective mechanical coverings.

1 . A drainage channel ( 203 ;  205 ) heating system comprising:
 a first terminal ( 215 ;  217 ) electrically coupled to a drainage channel at a first location;   a second terminal ( 219 ;  221 ) electrically coupled to a drainage channel at a second location, said first and said second terminals configured to define a resistance; and   a transformer ( 227 ) having a primary winding and a secondary winding ( 225 ), said secondary winding ( 225 ) coupled between said first terminal and said second terminal, wherein a predetermined secondary voltage is present at said secondary winding ( 225 ) when a predetermined primary voltage is impressed across connections of said primary winding ( 233 ), said predetermined secondary voltage for effecting a current in a drainage channel determined by said predetermined secondary voltage and said resistance.   
     
     
         2 . The system according to  claim 1  wherein said predetermined secondary voltage is in the range of from greater than 0 Volts to less than or equal to 6 Volts. 
     
     
         3 . The system according to  claim 2  wherein said drainage channel ( 203 ;  205 ) is electrically insulated. 
     
     
         4 . The system according to  claim 3  wherein said drainage channel is constructed of galvanized steel. 
     
     
         5 . The system according to  claim 4  wherein said first terminal ( 215 ) and said second terminal ( 219 ) are located on the same drainage channel ( 203 ). 
     
     
         6 . The system according to  claim 4  wherein said first terminal ( 215 ) and said second terminal ( 221 ) are located on different drainage channels ( 203 ;  205 ). 
     
     
         7 . The system according to  claim 6  wherein said predetermined secondary voltage is determined by a turns ratio. 
     
     
         8 . The system according to  claim 7  wherein said predetermined primary voltage ( 233 ) is determined based on said turns ratio and said predetermined secondary voltage. 
     
     
         9 . The system according to  claim 8  wherein the drainage channel heating system is for a heat pump evaporator assembly ( 101 ). 
     
     
         10 . A drainage channel ( 303 ;  305 ) heating system comprising:
 a conductive strip ( 307 ;  309 ) sized in matching correspondence with an interior of a drainage channel ( 303 ;  305 );   a first terminal ( 311 ;  313 ) electrically coupled to a conductive strip at a first location;   a second terminal ( 315 ;  317 ) electrically coupled to a conductive strip at a second location, said first and said second terminals configured to define a resistance; and   a transformer ( 321 ) having a primary winding and a secondary winding ( 319 ), said secondary winding ( 319 ) coupled between said first terminal and said second terminal, wherein a predetermined secondary voltage is present at said secondary winding ( 319 ) when a predetermined primary voltage is impressed across connections of said primary winding ( 233 ), said predetermined secondary voltage for effecting a current in a conductive strip determined by said predetermined secondary voltage and said resistance.   
     
     
         11 . The system according to  claim 10  wherein said predetermined secondary voltage is in the range of from greater than 0 Volts to less than or equal to 6 Volts. 
     
     
         12 . The system according to  claim 11  wherein said conductive strip ( 307 ;  309 ) is electrically insulated. 
     
     
         13 . The system according to  claim 12  wherein said conductive strip ( 307 ;  309 ) is coupled to an interior of a drainage channel ( 303 ;  305 ). 
     
     
         14 . The system according to  claim 13  wherein said first strip terminal ( 311 ) and said second strip terminal ( 315 ) are located on the same strip ( 307 ). 
     
     
         15 . The system according to  claim 13  wherein said first strip terminal ( 311 ) and said second strip terminal ( 317 ) are located on different strips ( 307 ;  309 ). 
     
     
         16 . The system according to  claim 15  wherein said predetermined secondary voltage is determined by a turns ratio ( 319 ). 
     
     
         17 . The system according to  claim 16  wherein said predetermined primary voltage ( 233 ) is determined based on said turns ratio and said predetermined secondary voltage. 
     
     
         18 . The system according to  claim 17  wherein the drainage channel heating system is for a heat pump evaporator assembly ( 101 ). 
     
     
         19 . A drainage channel comprising;
 a U-shaped structure having a bottom and two side walls;   a conductive material embedded within said drainage channel structure; and   a first terminal at a first end of the drainage channel and a second terminal at a second end of the drainage channel wherein said first and said second terminals conductively couple with said conductive material.   
     
     
         20 . The drainage channel according to  claim 19  wherein said conductive material is a metal. 
     
     
         21 . The drainage channel according to  claim 20  wherein said conductive metal is flat and sized in correspondence with said drainage channel bottom. 
     
     
         22 . The drainage channel according to  claim 20  wherein said conductive metal is U-shaped and sized in matching correspondence with said drainage channel bottom and sidewalls. 
     
     
         23 . The drainage channel according to Claim  19  wherein said conductive material is a conductive plastic. 
     
     
         24 . The drainage channel according to  claim 23  wherein said conductive plastic is said U-shaped structure.