Patent ID: 7640662

Claim:
A method of making a plastic heat exchanger for transferring heat from one gas to another while maintaining a barrier between them to isolate one gas from the other, providing a plurality of panels of plastic material, each having a substantial thickness and internal air cavities therein, and two opposed broad surfaces, pressure-forming at least one broad surface of selected ones of each of said panels to form at least one indentation in said one broad surface to form internal walls within said panel defining a recessed gas passage cavity in each, providing the others of said panels with elongated gas flow passages, interleaving said selected panels with said others of said panels in a predetermined sequence, and securing said panels together with broad surfaces thereof contacting one another, said gas passage cavities, together with surfaces of adjacent panels, forming conduits for one of said gases, and said elongated gas flow passages forming conduits for the other of said gases.