Numerical Study on the Mechanisms of Heat Transfer in Packed and Fluidized Configurations

A numerical investigation was carried out to examine heat transfer mechanisms in packed and fluidized beds through a coupled CFD-DEM approach. The column inlet is maintained at constant wall temperature for a range of temperatures at different fluid velocities tested. Two types of bed material were studied; aluminium and chromium oxide particles. The work comparatively analyzes the thermal behavior of fixed and fluidized regimes under the same operating conditions so as to clarify the role of particle motion in interphase heat transfer. CFD-DEM coupling results combined with thermal model are compared well to experimental results, and a consistency with published results of experiments. The simulations are indicates; that the heat transfer rate in packed beds is sensitive to material type that composed the particles, and particle size. While, the mechanisms of heat transfer in fluidized beds are more complex due to the motion of particles, and the interaction with fluid phase. Results show that convection was dominates in fluidized beds, with the heat exchange between fluid and particles, while the contribution of other two mechanisms (conduction and radiation) are decrease and decline from what their contribution to the fixed bed was. Hence, many variables in the fluidization process, like physical properties of the bed material, bed height, and fluid flow are affecting significantly the temperature profiles, and heat transfer. The findings provide mechanistic insights into thermal transport in multiphase systems and validation data for modify and develop the design of the fluidization units.