Unsteady-State Diffusion in Multicomponent Systems

Let us now turn our attention to multicomponent systems. An exact analytical solution of the multicomponent penetration model for ideal gas mixtures has been presented by Olivera-Fuentes and Pasquel-Guerra (1987). Their analysis, which, in many ways, is similar to the film model analysis of Section 8.3.5, is generalized below to any system described by constitutive relations of the form of Eqs. 2.2.9 or 3.2.5. 

In our analysis of the multicomponent penetration model we used the combined variable i = z/yfit. 

Following Olivera-Fuentes and Pasquel-Guerra (1987) we introduce transformed molar fluxes V  

The fluxes are assumed to be functions only of In terms of the mixture 

We must also write the one-dimensional form of Eq. 5.1.5 in terms of the Xi and as 

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