Wall Segment of Meshed Spheres

Simulations of heat transfer in fixed beds of discrete particles place severe demands on computational resources. The basic problem is the need to mesh the particles, to allow for solid conduction. Although a relatively coarse mesh would probably be sufficient inside the particles, the internal particle mesh is dictated by the surface mesh. This is, in turn, governed by the need for compatibility with the mesh in the fluid adjacent to the particle. That mesh, however, has to be very fine in order to properly represent flow near the particle-particle contact points, even with the use of near-wall models. To be able to get accurate enough results for specific regions in the bed simulation, a reduced size model can be created of a segment of the overall simulation model. The near-wall region is the logical section on which to focus. We have chosen to focus on a 120-degree “slice” of the bed cross-sectional area, as illustrated in the figure. For a wall-segment model, periodic boundary conditions on the top and bottom boundaries are necessary, and a layout that allows for these conditions, as well as the symmetry conditions on the side walls of the segment, is needed.