Faculty of Chemical Engineering, Amirkabir University of Technology, Tehran, I.R. IRAN
In thecomputational fluid dynamics (CFD) modeling of gas-solids two phase flow, the effect of boundary conditions play an important role in predicting the hydrodynamic characteristics of fluidized beds. In this work, the hydrodynamics of conical fluidized bed containing dried TiO2 nano-agglomerates were studied both experimentally and computationally. The pressure drop was obtained by pressure measurements and mean solid velocity in the different axial and radial positionsand their experimental values were measured by a parallel 3-fiber optical probe. The Eulerian-Eulerian multiphase model and granular kinetic theory with using Gidaspow (1994) drag function were applied in simulations. The effect of three different types of boundary conditions (BC) including no-slip/friction, free-slip/no-friction and high-slip/small-friction which were developed by Schaeffer (1987) and Johnson and Jackson (1987) were investigated. The results of the model were compared with the experimental data. The numerical simulation using free-slip/no-friction BC agreed reasonably well with the experimental pressure drop measurements. The pressure drops predicted by the simulations were in agreement with the experimental data at superficial gas velocities higher than the minimum fluidization velocity, Umf. The results for simulated mean axial solid velocity showed that the free-slip/no-friction BC was in better agreement with the experimental data compared with other boundary conditions.
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