Heat Transfer by Film Condensation : An Approximate Theory of Laminar-Film Condensation on a Vertical Wall

Abstract

An approximate theory, accounted for the effects of both energy convection and fluid acceleration within the film condense layer, is reported in this paper and the similar method (Karman-Pohlhausen's method) to the heat transfer by free convection has been used also for the laminarfilm condensation on a vertical wall. Heat transfer results are expressed by the following simple equations and indicate a good agreement with the numerical exact solutions for special Prandtl numbers, which have been given by Sparrow and Gregg recently. (I) for high Prandtl numbers [numerical formula] (II) for low Prandtl numbers [numerical formula] where β is a functon of Prandtl number and of cΔT/h_fg and is given by Figs. 2 and 3. The symbols used in the above equations are as follows : N_ux : local Nusselt number, k : thermal conductivity, h_fg : latent heat of condensation, c : specific heat, ΔT=T_sat-T_w ; T_sat : saturation temperature, T_w : wall temperature, g : acceleration due to gravity, ν : kinematic viscosity, ρ : condesate density, ρ_v : vapor density, x : distance measuring along wall from leading edge.