Abstract: A cross-flow heat exchanger unit comprising a plurality of corrugated film elements stacked in alternating layers such that the ridges and grooves of each film element extend transversely to those of an adjacent film element. Flat divider elements are interposed between each pair of adjacent film elements, and the structure is enclosed by a coating which bonds the elements together to form a rigid heat exchanger block. The film elements may be of non-metallic material, and the coating may be a curable, synthetic resinous material.

Abstract: An improved metallic heat transfer surface for heat transfer during change of phase of a medium in contact therewith and method of making. A smooth metallic surface is lightly etched to form evaporation and/or condensation nuclei. The nuclei are defined by peaks and valleys in the material, the peaks substantially extending to the envelope of the surface prior to etching and the vallyes extending into said material not more than 10.mu.(1.times.10.sup.-3 mm).

Abstract: Arrangements for directing flow through one or more modular, cross-flow heat exchanger units having primary and secondary flow channels of respective predetermined lengths. The units are arranged in a housing having primary and secondary flow inlet and outlet openings such that a primary flow path and a secondary flow path are defined. The portion of each flow path over which intensive heat exchange occurs is no longer than the length of the associated flow channels. The units may be stacked along one or more axes normal to the planes of the flow channels.