Mesoscale numerical simulation of heat transfer characteristics in spout bed based on LBM-DEM

In order to investigate the interaction mechanism between the dense gas⁃solid two⁃phase system in a spout bed，the LBM⁃DEM coupled flow and heat transfer model was established from the mesoscopic perspective based on the combination of the classical D2Q9 double distribution model of lattice Boltzmann method (LBM) and the soft sphere elastic model of the discrete element method (DEM). The numerical simulation of a micro⁃jet bed with differ⁃ ent jet incidence velocities was carried out using FORTRAN programming language，and the heat transfer characteris⁃ tics of dense gas⁃solid two⁃phase and two⁃phase in the bed were analyzed. At the same time，the simulation results were compared with experiments and relevant literatures，which effectively verified the accuracy of the model. The re⁃ sults show that the particles in the bed have a strong effect on the evolution of the gas temperature field. The larger the gas incidence velocity is，the faster the gas temperature field changes，and the temperature gradient distribu⁃ tion gradually presents an obvious S shape. The temperature increase rate of particles in different regions of the bed varies greatly，and the residence time of particles in the middle jet region is the main factor that determines the tempera⁃ ture difference between particles. The jet velocity is proportional to the overall heat transfer intensity in the bed，and its influence has a certain quantitative process. Convection is the main heat transfer mode in the micro⁃spout bed，which accounts for more than 99% under the temperature difference of 100 °C . The jet incidence velocity is positively corre⁃ lated with the convection and radiation heat transfer process in the bed，but negatively correlated with the heat conduc⁃ tion process. Within the velocity range of 0.5⁃0.9 m / s，the proportion of jet velocity on the three heat transfer modes in the bed is only about 1‰，so this effect can be ignored under the requirement of low accuracy. The above analysis results indicate that the mesoscopic LBM⁃DEM coupling model can be used as an effective means to analyze the flow and heat transfer mechanism in the dense fluid⁃solid two⁃phase system.