(561c) Continuum Simulations of Heat and Mass Transfer in Wet Granular Mixtures

The rheology and hydrodynamics of wet granular mixtures are important in many industrial processes such as pharmaceutical and agricultural production, and petrochemical refining. Heat and mass transfer considerations are also important in key industrial processes involving solvent removal by thermal drying of powders and the product of wet granulation. Continuum simulations involve solving the averaged equations for conservation of mass, momentum, and energy by treating the granular medium as a continuum. In this study, we develop an analytical model for verifying Computational Fluid Dynamics (CFD) simulation results in a cylinder filled with stationary wet granular material. The analytical model solves for the unsteady axisymmetric temperature field during transient heating of the wet granular material to the saturation temperature and the steady axisymmetric temperature field during drying of the wet granular mixture. In order to obtain tractable analytical solutions, it is assumed in the analytical model that there is no mass transfer during the transient heating phase and that all mass transfer occurs at the steady temperature distribution corresponding to the drying stage through a specified sink term in the heat equation. Continuum simulations of heat transfer in the stationary granular bed are performed and the results are verified with those of the analytical model. Further realities of particle drying due to solvent boiling and wet bulb evaporation mechanisms are incorporated into a coupled heat and mass transfer CFD simulation to obtain more realistic results. The assumptions made in the analytical model are also quantitatively examined using the continuum simulations.