(185d) Multicomponent Diffusion: Tests of Existing Theories

Molecular diffusion in multicomponent systems has been the subject of many theoretical studies. Problem with many of these approaches is that they violate material balance constraint and lead to non-physical predictions. Theories by Zielinski and Hanley, Alsoy and Duda have been tested and negative concentrations are observed for the balancing third component. The proportionality assumption between the self-diffusivity and molecular weight (M) made by Price and Romdhane in their generalized model eliminated the problem. However such a restriction is not applicable for high polymer systems were diffusivity is proportional to M^-2. The proportional flux model introduced by Nauman and Savoca takes care of the problem without the need to constrain the self-diffusivity to the molecular weight.