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

• Published in: Chemical engineering science 2006-03, Vol.61 (5), p.1692-1704
• Main Authors: Valdés-Parada, Francisco J., Goyeau, Benoıˆt, Alberto Ochoa-Tapia, J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Closure problem; Diffusion; Exact sciences and technology; General and physical chemistry; Heat and mass transfer. Packings, plates; Homogenization; Microstructure; Porous media; Reaction jump coefficient; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2005.10.005

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 · ( ε 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.