Infra-red radiant panel heater using PTC conductive polymeric electrodes

Abstract

An infrared radiant panel heater utilizing a liquid-tight enclosure with at least one surface emissive of infrared energy by liquid inside the enclosure. A pair of polymeric electrodes having the property of positive temperature cut off are submerged in the liquid inside the enclosure, near the bottom thereof. Liquid is heated by electrical current flowing through the liquid between the electrodes. Convective flow of liquid distributes heated liquid throughout the enclosure. The cutoff temperature can be selected by electrolyte concentration in the liquid (usually water and sodium chloride) and the properties of the electrodes. In some embodiments a reversed face of the enclosure is reflective, so that most of the infrared energy is directed into the room rather than against a wall.

1 . An infrared wavelength emitting heater comprising: 
 an enclosure having a pair of spaced-apart opposite sides joined at their periphery to form an internal liquid-tight cavity, at least one of said sides including a surface from which infrared wavelength energy will be emitted as the consequence of the temperature of liquid in said cavity;    an electrode assembly in said enclosure near the bottom and between said sides, said electrodes being spaced apart from one another, said electrodes being connectable to a source of electrical current;    fluid-flow passages in said enclosure so disposed and arranged as to encourage liquid heated by said electrode assembly to rise toward the top and return downwardly along the sides to the electrode assembly;    liquid in said enclosure having a known electrical resistance for joule heating by electrical current flowing through it between said electrodes;    said electrodes being submersed in said liquid with said liquid between them, and comprising a polymeric material with a positive temperature coefficient such that at a known cut-off temperature of the electrodes, the resistance of the electrodes to current flow rises to materially reduce or to cut-off flow of electrical current through them, said cut-off temperature being attained in response to resistance heating of the electrodes themselves and of the temperature of the liquid in which it is submersed.    
   
   
       2 . A heater according to  claim 1  in which said surface is constituted to emit said infrared energy.  
   
   
       3 . A heater according to  claim 2  in which said surface is formed to be a front side and the other side is a second side opposite to it and formed of material not transmissive of infrared energy, whereby the major portion of infrared energy is emitted from said surface.  
   
   
       4 . A heater in which a liquid-tight bladder is fitted inside said enclosure to hold said liquid, with the electrodes disposed in the bladder, the bladder being in surface to surface contact with the inside of said sides.  
   
   
       5 . A heater according to  claim 4  in which the bladder is substantially formed of resilient material, having a pair of opposite sides, said opposite sides being locally joined to provide said flow channels between them when the bladder filled with liquid.  
   
   
       6 . A heater according to  claim 1  in which said electrodes are separated by insulation to provide said spacing in which liquid is to be heated.  
   
   
       7 . A heater according to  claim 5  in which said electrodes are separated by insulation to provide said spacing in which liquid is to be heated.  
   
   
       8 . A heater according to  claim 1  in which said liquid is water in which an electrolyte is dissolved in concentration known to produce an electrical resistance between said electrodes which enables the water to be joule heated to a temperature at least as high as the cut-off temperature.  
   
   
       9 . A heater according to  claim 5  in which said electrolyte comprises sodium chloride.  
   
   
       10 . A heater according to  claim 5  in which said liquid is water in which an electrolyte is dissolved in concentration known to produce an electrical resistance between said electrodes which enables the water to be joule heated to a temperature at least as high as the cut-off temperature.  
   
   
       11 . A heater according to  claim 10  in which said electrolyte comprises sodium chloride.  
   
   
       12 . A heater according to  claim 2  in which both sides include a said infrared wavelength energy emitting surface.  
   
   
       13 . A heater according to  claim 12  in which a stand supports said heater, whereby it can be placed where infrared energy is desired from both sides.  
   
   
       14 . A heater according to  claim 3  in which means is provided to mount the heater to a wall, said other side being reflective of said energy.