A systematic approach to defining a unit cell for fluid dynamics in packed beds with low tube-to-particle diameter ratio

Abstract

This work develops an approach to identify the suitable representative volume (unit cell) that captures fluid dynamics in beds packed with spheres or cylinders with a d_t/d_p ≤ 10, by describing radial void fraction and velocity profiles at particle Reynolds numbers between 5 and 100. Rigid-body simulations were used to construct synthetic packings, while velocity profiles were obtained from particle-resolved simulations. This methodology, rooted in the similitude of fluid dynamics between beds of different lengths, determines the minimum length (or number of particles in a bed) required for the unit cell to accurately describe the void fraction and velocity profiles. Defining such a unit cell for fluid dynamics not only reduces computational effort but also opens avenues for its use in multiscale techniques to develop reliable pseudo-continuous models, which is currently the bottleneck in the design and optimization of wall-cooled packed-bed reactors in industrial scenarios.