Effects of a small amount of noncondensable gas on film condensation of multicomponent mixtures

Abstract

The effects of a small amount of noncondensable gas on film condensation of multicomponent vapor mixtures are analytically studied. The governing equations of mass transfer and phase equilibrium of multicomponent species at the liquid-vapor interface are solved with perturbation due to the addition of a small amount of noncondensable gas to the main vapor mixture to obtain its behavior in the process of film condensation. Generally, the overall condensation rate is not always to be decreased with introducing the noncondensable gas into the multicomponent mixture. For small temperature difference across the condensate layer, the condensation rate decreases proportionally to the mole fraction of noncondensable gas accumulated at the interface. The results are applied for two binary systems of condensable and condensable species as well as condensable and noncondensable species with a numerical example.