286117 Effective Medium Theory for the Transport of Fluid Mixtures Through Porous Media
The transport of fluids in the narrow confined pore spaces disordered materials with complex pore topologies is central to many emerging technologies for gas separation and storage, as well as in nanofluidics. Optimizing the performance of such technologies requires a deep understanding of how the flow of these mixtures is affected by the topology of the pore space, particularly its pore size distribution and pore connectivity. While there exist accurate techniques such as the hybrid effective medium-correlated random walk theory for the estimation of the effective diffusivity characterizing the transport of single fluids through porous materials, equivalent approaches for the case of fluid mixtures are yet to be developed. Existing alternatives for multi-component systems rely on computationally intensive solution of the pore network equations, or ad hoc adaptations of the single fluid theories which are useful for a limited variety of systems. We present here a hybrid Effective Medium-Correlated Random Walk Theory for the calculation of the matrix of effective transport coefficients of fluid mixtures diffusing through porous materials. The theory is suitable for those systems in which component fluxes at the single pore level can be related to the chemical potential gradients of the different species through linear flux laws, and corresponds to a generalization of the classical single fluid effective medium theory for the analysis of random resistor networks. Comparison with simulation of the diffusion of binary CO2/H2S and ternary CO2/H2S/C3H8 gas mixtures in membranes modeled as large networks of randomly oriented pores with both continuous and discrete pore size distributions demonstrates the power of the theory, which was tested using the well known generalized Maxwell-Stefan model for surface diffusion at the single pore level.
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