Forced Convection in Packed Tubes and Channels with Variable Porosity and Thermal Dispersion Effects

Abstract

Previous work in chemical engineering literature on the determination of the effective transverse thermal conductivity and Nusselt number for forced convection in packed tubes and channels are reviewed. Discrepancies in existing Nusselt number correlation equations are discussed. Some of the existing experimental data are reanalyzed based on the recent thermal dispersion theory developed by Hsu and Cheng with variable porosity effects taken into consideration in an approximate manner. Numerical results are obtained for forced convection of air and water in packed tubes and channels. For forced convection in a packed column, it is found that the average Nusselt number depends not only on the Reynolds number, but also on the dimensionless particle diameter, the dimensionless length of the tube, the thermal conductivity ratio of the fluid phase to the solid phase, and the Prandtl number of the fluid.