CFD SIMULATION OF GAS-SOLID BUBBLING FLUIDIZED BED: A NEW METHOD FOR ADJUSTING DRAG LAW

In computational fluid dynamics modelling of gas solid two phase flow, drag force is one of the dominant mechanisms for interphase momentum transfer. Despite the profusion of drag models, none of the available drag functions gives accurate results in their own original form. In this work the drag correlations of Syamlal and O'Brien (Syamlal and O'Brien, Int. J. Multiphase Flow. 1988; 14(4):473-481), Gidaspow (Gidaspow, Appl. Mech. Rev. 1986; 39:1-23), Wen and Yu (Wen and Yu, Chem. Eng. Prog. Symp. Ser. 1966; 62(2):100-111), Arastoopour et al. (Arastoopour et al., Powder Technol. 1990; 62(2): 163-170), Gibilaro et al. (Gibilaro et al., Chem. Eng. Sci. 1985; 40:1817-1823), Di Felice (Di Felice, Int. J. Multiphase Flow. 1994; 20(1):153 159), Zhang-Reese (Zhang and Reese, Chem. Eng, Sci. 2003; 58(8):1641-1644) and Hill et al. (Hill et al., J. Fluid Mech. 2001; 448:243-278) are reviewed using a multi-fluid model of FLUENT V6.3.26 (FLUENT, 2007. Fluent 6.3 User's Guide, 23.5 Eulerian Model, Fluent, Inc.) software with the resulting hydrodynamics parameters being compared with experimental data. The main contribution of this work is to propose an easy to implement and efficient method for adjustment of Di Felice drag law which is more efficient compared to the one proposed by Syamial-O'Brien. The new method adopted in this work showed a quantitative improvement compared to the adjusted drag model of Syamlal-O'Brien. Prediction of bed expansion and pressure drop showed excellent agreement with results of experiments conducted in a Plexiglas fluidized bed. A mesh size sensitivity analysis with varied interval spacing showed that mesh interval spacing with 18 times the particle diameter and using higher order discretization methods produces acceptable results.