Diffusive mass transfer between a microporous medium and an homogeneous fluid: Jump boundary conditions

Abstract The method of volume averaging is used to derive the diffusive mass transfer boundary conditions for transport between the micro-pores ( ω -region) and the fluid in the macro-pores ( η -region) in a catalyst pellet. In this configuration, the mass jump boundary condition between the homogeneous regions takes the form - n η ω · ( D γ ∇ 〈 c A γ 〉 η γ ) + n η ω · ( e γ D ω · ∇ 〈 c A γ 〉 ω γ ) = K eff 〈 c A γ 〉 ω γ , where K eff is the effective reaction rate coefficient at the inter-region. In this study, a closure is derived in order to predict this average jump coefficient as a function of the microstructure of the porous layer and the Thiele modulus. The jump coefficient predicted for three inter-region structures is presented.

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