Laminar Film Condensation in the Subcritical Region : Gravity Controlled Condensation

Abstract

This paper treats laminar film condensation of vapours in the subcritical region. The similarity solusions for gravity controlled condensation of pure vapours of water and carbon dioxide on a vertical plate are numerically obtained. The effects of small latent heat, low ρ-μ ratio and high Prandtl number on the boundary values, temperature distribution in the liquid film and velocity distribution in the boundary layer are revealed. The dimensionless expressions for the heat transfer coefficient and the condensate mass flux are derived, which contain the characteristics of Nusselt's theory as a special case. When the reduced temperature of the vapour approaches unity and the temperature difference between vapour and wall is large, the effect of the convection term in the liquid film appears markedly and the heat transfer coefficient becomes independent of H, but depends on Gr_Lx and Pr_L.