Controlled performance heat exchanger for evaporative and condensing processes

A heat exchanger structure particularly adapted for liquid-to-gas heat transfer comprising a multiplicity of spaced parallel heat transfer plates in fixed relationship and being in thermal contact with an external fluid medium, a multiplicity of spaced parallel axis tapered telescopically interfitting cup-like elements formed integrally on said plates and projecting from corresponding surfaces of the plates in coaxial relationship to form fixed parallel columns through the plates at right angles to the planes occupied by the plates and across the spaces between the plates, whereby such spaces surround the columns formed by the cup-like elements, coaxial spaced nozzle elements integral with the cup-like elements and projecting therefrom coaxially in spaced relationship and in one direction to form through the centers of said columns gas flow passages which are isolated from the spaces between said plates, portions of the cup-like elements surrounding said nozzle elements forming liquid traps in the columns, and gas pressure responsive liquid delivery means at one end of each column operable to deliver liquid into the columns in counter-flow relationship to the gas flow therethrough, whereby small amounts of the liquid can enter said traps and be held therein.