Fluid flow through catalyst filled tubes

A detailed knowledge of the fluid flow profile is essential for a proper design of fixed-bed processes. For different sphere, ring and cylinder sizes, radial velocity profiles were measured below the bed at empty tube velocities of air of 0.5 m/s < v(0) < 1.5 m/s and the tube-to-particle diameter ratios 3.3 < d(t)/d(p) < 11. The profiles show a velocity maximum in the vicinity of the wall. As a consequence of the statistical behaviour of packings, it was necessary to average velocity measurements after repacking in order to obtain representative flow profiles. These averaged profiles were the basis for a model through which the flow profile inside the packing can be calculated for spheres, cylinders and rings. The model is based upon the extended Brinkman equation and the independently determined radial void fraction profiles. It considers an 'effective viscosity' for which correlations have been derived. Comparison of simulated velocity profiles with exemplary liquid flow measurements inside the packed bed of Vortmeyer and co-workers shows reasonable agreement. (C) 1997 Elsevier Science Ltd.