Condensation of pure steam and steam-air mixture with surface waves of condensate film on a vertical wall

Abstract

A series of experiments has been conducted to investigate the effect of wavy interface on film condensation with and without a noncondensable gas present on a vertical wall. Concurrently, the instantaneous film thickness was measured. Overall heat transfer coefficients across the condensate film and the diffusion layer formed by a noncondensable gas were obtained in various parameters such as air-mass fraction (W = 0.1–0.7), mixture vapor velocity (Uin = 3, 5, 7 m/s) and condensate film Reynolds number (Reff,in= 0–19,000). In order to investigate the heat transfer enhancement induced by a dynamic interaction of the surface waves on condensate and the diffusion layer, vapor-side heat transfer coefficient was estimated from the measured overall heat transfer coefficient and the correlation of film-side heat transfer coefficient, and compared with that estimated by Colburn and Chilton-Colburn analogy for a smooth flat plate. The comparison showed that the vapor-side heat transfer coefficient increased clearly with the increase of film Reynolds number. The enhancement effect was dominant for low mixture vapor velocity and decreased with the increase of mixture vapor velocity.