Anomalous diffusion-controlled evaporation

Abstract

Diffusion-controlled, steady-state evaporation through certain membranes has been reported to proceed anomalously faster into a humid than into a dry atmosphere. The diffusion coefficient of such a membrane depends explicitly on both concentration and location within the membrane. Moreover, the membrane has a skin at its evaporating surface, the non-zero thickness of which is independent of atmospheric concentration. The inner surface of the skin is characterised by the steady-state diffusion coefficient becoming zero or infinite there. Examples are given of hypothetical diffusion coefficients that yield the anomalous evaporative behaviour considered.