Evaluation of interphase drag models for the determination of gas hold-up of an air-water system in a spouted bed using CFD

Abstract

The hydrodynamics of a dispersed air-water system within a spouted column with a concentric draft tube and a conical base is simulated using CFD based on a two-fluid Euler-Euler E-E modeling framework and k-e two-equation turbulence closure. The interaction between the dispersed gas phase and the continuous liquid phase is characterized by bubble-liquid interphase forces drag, turbulent dispersion and lift forces. The Ishii-Zuber drag model [1] and Grace adjusted drag model [2], the latter represented by: C_D^{Grace,dense} = υ _g^p C_D^{Grace}, are compared for their capability to match experimental gas hold-up. Numerical results of Reynolds-averaged Navier-Stokes equations with k-e two-equation turbulence closure model when compared with Pironti experimental data [3] indicated that both drag models, predicted the air hold-up within experimental errors. Furthermore, Ishii-Zuber liquid-gas drag model consistently provided better agreement with experimental results; it correctly determines the hold-up within 0.14%. Numerical agreement with adjusted Grace liquid-gas drag model, is exponent dependent 4 ≤ p ≤-0.5, turning down that the best computed hold-up is within 0.44% for p=0.5.