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.