Direct numerical simulation of flow and heat transfer in bidisperse gas-solid systems

The flow and heat transfer in bidisperse gas-solid systems with particle diameter ratio ranging from 1:2 to 1:4 have been numerically investigated via an immersed boundary-lattice Boltzmann method. The modeling for the overall Nusselt number (Nu) is pursued. The results show that the overall Nu obtained from the simulation results can be predicted well using the monodisperse correlations by defining an appropriate equivalent diameter. An accurate model to predict Nu for each species is formulated through a correction to the monodisperse heat transfer correlations. Since the relative solid volume fraction ratio of large-to-small spheres has marginal influence on Nu for each species, the correction term is only closed as a function of the total solid volume fraction and scaled particle diameter. The predictability of the model is evaluated. The results demonstrate that the model can give more accurate estimations for Nu of each species. (c) 2021 Elsevier Ltd. All rights reserved.