CFD analysis of thermal dispersion in a structured packed bed

Abstract

Packed beds are generally modelled in a partial manner to avoid computational costs. This implies that only a small portion of the representative bed is modelled explicitly in CFD simulations, usually by assuming symmetry boundary conditions. Thermal dispersion requires both the small and large-scale fluid flow phenomena to be resolved. Consequently, it is required to model a large portion of the original packed bed. In this study, the original model consisted of approximately 4000 uniform spheres in a body-centered cubic (BCC) packing-structure with no contact between the spheres. A braiding effect was induced by allowing cold and hot nitrogen streams to mix within the packed region. The apparent unsteady, oscillating nature of the flow in numerous cells can result in simulation difficulties. To overcome these difficulties, an appropriate simulation methodology was developed using STARCCM+ by investigating the effect of several simulation parameters on the mesh quality, residuals and temperature profiles. Good agreement between the numerical results and experimentally measured temperatures has been achieved by using a locally refined mesh with the Large Eddy Simulation (LES) model