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 micropores ((omega)-region) and the fluid in the macro-pores ((eta)-region) in a catalyst pellet. In this configuration, the mass jump boundary condition between the homogeneous regions takes the form -n(eta)(omega).(D(gamma)^(nabla)(gamma)^(eta))+n(eta)(omega).((omega)(gamma)D(omega).(nabla) (omega)^(gamma))= Keff(gamma) )(omega) where Keff 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.