Abstract
Longitudinal rectangular fins loosely clamped to vertical tubes markedly increase the film condensation heat transfer coefficient. At a heat flux of 2×104B.t.u./hr.sq.ft., twelve ⅛×0.013 fins clamped to a ½ in. O.D. vertical tube 42 ½ in. long (thus doubling the surface area of the tube) gave a condensation coefficient of 15,000 ± 15% B.t.u./hr.sq.ft. °F. compared with 1,620 B.t.u./hr.sq.ft. °F. for the same tube without fins, a ratio ofh/hoof 9.2. The enhancement of the film condensation coefficient decreases as the heat flux increases and as the number of fins decreases.A model based on the effect of fin shape on film and rivulet hydrodynamics explains the observed behavior.

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