Heat exchangers

Claim 1

A heat exchanging method for generating a vapor from a liquid while preventing a dry out condition in the tubes of a heat exchanging device comprising the steps of: providing a heat exchanging device comprising an inlet located at a lower portion of said heat exchanging device, an outlet located at an upper portion of said heat exchanging device and internal heat transfer tube assemblies mounted in a fluid flow path of said device between said inlet and outlet, each tube assembly comprising a tube and a plurality of plate-like fins secured to the outer surface of said tube to extend radially therefrom, said tubes being arranged horizontally and each of said fins being secured to the outer peripheral surface of only the lower half of an associated tube from one side thereof to the other and functioning to prevent overheating of an upper half of the associated tube; feeding a high temperature gas into the inlet of said heat exchanging device and through said fluid flow path; and passing a liquid through said tube assemblies and vaporizing said liquid by heat from said high temperature gas to form within at least one of said tubes a liquid vapor and a thin liquid film along an upper inner wall of said at least one tube, said fins which are only at the lower surface of said tubes preventing the overheating of an upper half of said at least one tube and a drying out of said thin liquid film therein.