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

The method of volume averaging is used to derive the diffusive mass transfer boundary conditions for transport between the micro-pores (ωω-region) and the fluid in the macro-pores (ηη-region) in a catalyst pellet. In this configuration, the mass jump boundary condition between the homogeneous regions takes the form-nηω·(Dγ∇〈cAγ〉ηγ)+nηω·(εγDω·∇〈cAγ〉ωγ)=Keff〈cAγ〉ωγ,where KeffKeff 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.