Effect of Schmidt number and D/d ratio on mass transfer through gas-solid and liquid-solid packed beds: Direct numerical simulations

摘要

The effect of Schmidt number (Sc) and D/d ratio on mass transfer through gas-solid and liquid-solid packed beds was studied. The parameters investigated in this study were Sc = 1, 10, 100 and 1000, Re <= 100, D/d = 6 and 11, and the void fraction was kept constant at 0.57. DEM-CFD simulations were conducted to create the random geometry of the packed bed. Model validation and mesh independency was performed, and good agreement with the experimental results was noted. Overall Sherwood number (Sh(o)) along with the local Sherwood number (Sh(L)) around each particle in the packed bed was estimated. It was observed that the Sh(o) increases with Re, and the slope of the relationship between Sh(o) and Re increases with increasing Sc. An interesting trend was also reported, which signifies the combined effect of Sc and D/d ratio on mass transfer. It was noticed that, at Sc = 1, the Sh(o) vs Re trend for D/d = 6 was below the one for D/d = 11. However, as Sc further increases, the trend for D/d = 6 moves above the one for D/d = 11. This behavior is due to the presence of boundary effects. The findings were further supported by the probability distribution curves of the local Sherwood numbers in the packed bed, and the area weighted average of mass fraction of solute with respect to the axial coordinate of the packed bed. (C) 2019 Elsevier B.V. All rights reserved.