The Concept of Augmented Diffusivity by Convection

Analysis of tracer experiments in chromatographic columns with a conventional model that combines convection and diffusion inside pores is based on the mass balance in a volume element for a slab adsorbent particle  

The particle transfer function relating the average concentration inside particle and the particle surface concentration is  

On the other hand the analysis by a detailed diffusion/convection model leads to a mass-balance equation in a slab adsorbent particle which includes terms relating to diffusive flux, convective flux and accumulation  

Model equivalence (Fig. 3.4-5) leads to Eq. 4 where the enhancement factor for pore diffusivity due to convection is 1//(A) shown in Fig. 3.4-6, with 

The key parameter is the intrapartide Pedet number defined as the ratio between the time constant for pore diffusion and the time constant for intrapartide convection. There are two limiting situations  

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