Particle scale modeling of heat transfer between mesoscale clusters and surfaces in fluidized beds

Abstract

The distribution of heat absorption and the mechanisms of conductive, convective, and radiative heat transfers between cold particle clusters (Tp = 300 K) and high-temperature surfaces (Tw = 1173 K) in fluidized beds were investigated through numerical simulations using the MFiX-DEM approach. The influence of cluster characteristics (εc and Dc), restitution coefficients (ep and ew), and particle properties (dp, ρp, kp, and cp) on heat absorption and various heat transfers was examined. The simulations indicate that convection predominantly governed the heat transfer behavior during the process of mesoscale clusters impacting the surfaces. A significant increase in heat transfer can be attained by reducing the cluster volume fraction, cluster size, particle diameter, and particle density. Besides, decreasing the restitution coefficients allowed for a relatively small enhancement of heat absorption. The maximum difference in ep was 2.11 kW/kg, while the maximum difference in ew was 0.99 kW/kg. The specific heat capacity and thermal conductivity of the particle had little influence on the distribution of heat absorption and heat transfer with a maximum relative error of up to 5.8 %. Finally, the mathematical correlation during surface-to-cluster heat transfer was established. This work introduces a novel application of the MFiX-DEM approach to analyze surface-to-cluster heat transfer at the particle scale, providing valuable insights for optimizing fluidized bed systems.