Heat Transport in Wall-Cooled Packed Beds of Low Tube-to-Particle Diameter Ratio

摘要

The influence of a radial porosity and velocity profile on the predictedtemperature and concentration profiles in wall-cooled packed beds is studied, with and without an exothermic first-order chemical reaction, on the basis of correlations taken from literature. The radial porosity and velocity profiles are approximated by a step-function. It is shown that the effective radial heat conductivity can be taken constant over the radius, despite the wall effect. Nevertheless, the influence of the radial velocity profile can be significant through the convective term in the heat balance, especially for low tube-to-particle diameter ratios. The predicted NTU can increase in the order of 20% for high values of the Reynolds number and up to 100% for low values. In case of a first-order exothermic reaction, significantly higher values for the hot-spot temperatures are predicted, if a radial porosity and velocity profile is incorporated in the heat and mass balances. (Copyright (c) 1991 by J.G.H. Borkink, Enschede, The Netherlands.)