Method and device for defrosting heat exchanger without impairment of its heat exchange efficiency

Claim 1

In the method of defrosting a heat exchanger without substantial impairment of the thermodynamic exchange efficiency of the exchanger, which comprises a pack of facially opposed heat exchange surfaces defining therebetween a plurality of open-ended channels in which a stream of relatively cold medium is passed through one set of channels in heat exchange relationship with a stream of relatively warm medium passed through another set of channels, which channels terminate in an inlet surface area and an outlet surface area for the respective sets of channels which surface areas extend across said pack, the improvement comprising: continuiusly controlling the proportions of the two streams by blocking off a portion of the surface area for the cold medium to periodically interrupt the flow of cold medium through at least one cold medium channels at a time along the surface area of said blocked off portion in response to environmental thermodynamic conditions while maintaining the flow of warm medium through the set of warm medium channels uninterrupted to heat the exchange surfaces of the frosted channels so as to maintain the channels free of ice without substantially impairing the thermodynamic exchange efficiency thereof.