Heat exchanger with leakage collector

Claim 1

A heat exchanger for transferring heat between a first liquid and a second liquid comprising: a heat exchanger shell member having a central portion extending between and terminating in two end portions which respectively include an inlet duct and an outlet duct for said liquid; a double-walled member of the heat exchanger comprising two tubes including an outer tube of one diameter having outwardly extending fins, and an inner tube of smaller diameter extending concentrically through the outer tube and being a snug fit therewithin, the inner tube carrying said second liquid, the outer tube comprising a seamless tube having a helical fin integrally formed on its outer surface, and its inner surface having an undulating helical pattern of ridges and depressions whose pitch is the same as the pitch of the helical fin; an annular core member extending lengthwise in the central portion of the shell member, the diameter of the core member being within a range extending from about the diameter of said outer tube as measured without the fins to about twice that diameter; the double-walled member being distorted to form a helical volute tightly surrounding said core member for a length about equal to the length of said central portion of the shell member so that the fins of successive convolutions substantially lie against the core member, and the inside diameter of the central portion of the shell member being about equal to the outer diameter of the convolutions of the volute as measured to the outer surfaces of the fins; the outer tube of the double-walled member being elliptical in cross-section with said ridges pressed tightly against and distorting the outer surface of the inner tube to form tube zones having a high degree of mutual contact; the outer tube of the double-walled member having ends which are aligned along the axis of the helical volute and are spaced apart therealong by a distance greater than the length of the heat exchanger shell member, the outer tube being integrally continuous between its outer ends; and the volute being contained in the central portion of the shell member and the ends of the outer tube being free of fins and extending through and to the outside of both end portions of the shell member and having their external peripheries sealed to the shell member where they pass through each end portion, and the inner tube extending from the shell member beyond said sealed peripheries of the outer tube ends, whereby any leakage of either tube will escape between the tubes and discharge outside of the shell member.