Unsteady multicomponent diffusional evaporation



The unsteady diffusion-controlled evaporation of a pure fluid into a multicomponent mixture is studied by a boundary-layer method. An expression is obtained for the volume of vapor produced by the evaporating species as a function of time. It is shown that the result can be interpreted in terms of an effective diffusivity of the type proposed by Wilke and by Stewart. It is further demonstrated that the boundary-layer method predicts a sweep-diffusion effect.