Thermal transfer care

A heat exchanger for transmitting thermal energy from one moving body of fluid to another comprising a casing of substantially constant cross-sectional area and a thermal transfer core within said casing, said core including a single, integrally formed, substantially continuous sheet of heat conductive material having a plurality of fold sections, separated by fold lines, the individual fold sections of said sheet dividing the interior of said casing into adjacent fluid flow passages, alternate ones of said passage defining first conduit means for conducting relatively warm fluids, the other passages defining second conduit means for conducting relatively cool fluids, said casing having first and second pairs of inlet and outlet openings formed therein, said first and second pairs of openings communicating with said first and second conduit means respectively, the individual fold sections of said sheet having a multiplicity of pairs of dimples formed therein, said dimple pairs being aligned longitudinally with respect to each other in at least two longitudinally extending zones, each said pair of dimples comprising a raised dimple and an adjacent depressed dimple wherein the spacing between the raised and depressed dimple in each dimple pair is small with respect to the spacing between adjacent, longitudinally aligned pairs of dimples, the height of each dimple being substantially equal to one-half the width of said fluid flow passages, the individual fold sections of said sheet each having longitudinally extending ridges formed therein, each ridge being formed between zones of aligned dimple pairs of extending over the substantial length of said fold section and each ridge terminating before the next adjacent fold section, the terminal ends of said ridges in each fold section defining a fold line between the adjacent fold sections, said dimple pairs being located in said fold sections so that upon folding said sheet of heat conductive material upon said fold lines in opposite directions alternately, raised and depressed dimples in each dimple pair are in opposed, abutting relationship with corresponding raised and depressed dimples in adjacent fold sections, whereby said opposed, abutting dimples provide spacing between and mutual support for adjacent fold sections, said spacing between adjacnt fold sections defining said fluid flow passages in a manner such that the fluid pressure drop through the heat exchanger is reduced.