Heat exchangers and method of making same

Claim 1

A heat transfer element comprising a. an elongated tubular member having a horizontal center line therein, b. said tubular member having a top and bottom wall integral therewith, said top wall and said bottom wall each having a substantially rectangular-shaped facing thereon, c. at least two groups of fins spaced from each other longitudinally along both of said top and bottom walls, each group comprising a plurality of cut fins, said cut fins spaced from each other longitudinally therealong, with said at least two groups of fins along both of said top and bottom walls having a spacing therebetween formed by predetermined severing of the cut fins and providing fin stubs thereon, with the outer surface of said spacing therebetween defined by said severed fin stubs presenting substantially a horizontal outer plane surface with respect to said horizontal center line of said tubular member, d. each of said fins in each of said groups (1) being spaced from the next adjacent fin a predetermined distance longitudinally along both said top and bottom walls, and (2) projecting outwardly from said face, said groups of fins being spaced from each other a distance greater than said predetermined distance longitudinally along said wall, e. said tubular member further having two oppositely disposed end portions adjacent one of said group of fins on both said top and bottom walls, f. each of said end portions having (1) an inner surface portion sloping upwardly and outwardly from the respective adjacent group of said fins, and (2) an outer surface portion extending outwardly from said inner portion thereof in substantially parallel relation to the center line of said tubular member.