Film model for mass transfer in non-ideal multicomponent fluid mixtures

Abstract

Multicomponent film model equations in the framework of generalized Maxwell-Stefan model were solved for non-ideal fluid mixtures for any given composition dependence of concentration, diffusivities and thermodynamic non-idealities. The solution is valid for planar, cylindrical and spherical film geometries. This proposed solution was used to evaluate the available approximate solutions and to examine the conditions under which they perform well. On the basis of calculations for the system acetone-benzene-carbon tetrachloride, it was observed that approximate methods generally give rise to greater errors in calculating small fluxes, i.e. when components transfer under small values of driving force. A parameter a was defined for each component to assess the influence of varying physical properties on the error associated with approximate methods. When α 15% the error is about 6% and, when a 25%, the corresponding errors are greater than 18%. Whenever the approximate methods may be used for calculation, their performances are similar, but the method based on effective diffusivities has the advantage of being simple.