Diffusion Layer Modeling for Condensation With Multicomponent Noncondensable Gases

Many condensation problems involving noncondensable gases have multiple noncondensable species, for example, air (with nitrogen, oxygen, arid other gases); and other problems where light gases like hydrogen may mix with heavier gases like nitrogen. Particularly when the binary mass diffusion coefficients of the noncondensable species are substantially different, the noncondensable species tend to segregate in the condensation boundary layer. This paper presents a fundamental analysis of the mass transport with multiple noncondensable species, identifying a simple method to calculate an effective mass diffusion coefficient that can be used with the simple diffusion layer model. The results are illustrated with quantitative examples to demonstrate the potential importance of multicomponent noncondensable gas effects.