Abstract

CFD modeling of fixed bed reactors is indispensable for understanding and optimization of its internal heat and mass dispersion. Those CFD models were earlier developed with continuum approach for high tube-to-particle diameter ratio (Np) beds. Particle-resolved CFD models followed, in spite of much higher computational cost, for investigating low Np bed with high heat flux, in which transport phenomena at near wall region with high porosity significantly affects the entire bed performance. Although segmented-continuum approaches were recently paid attention again, the validity and applicability regarding the extent of near-wall region and simplification of porosity distribution have not been carefully discussed yet.In this study, two of segmented-continuum approaches, namely, (Approach 1) two lumped segments and (Approach 2) near-wall-detailed and bulk-lumped segments approaches, were proposed and examined for CFD modelling of sphere fixed bed. The numerical results of those approaches were validated using experimental and particle-resolved CFD simulation data in the literature. In terms of heat dispersion, both approaches were in good agreement with the experimental data. However, the model accuracy in terms of mass dispersion was sensitive to the near-wall treatments because mass diffusion in fluid phase was much higher than that in solid phase of particles.

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