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-𝜀 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: ${\mathit{C}}_{\mathit{D}}^{\mathit{Grace}\mathrm{,}\mathit{dense}}$ = ${\mathit{\upsilon }}_{\mathit{g}}^{\mathit{p}}{\mathit{C}}_{\mathit{D}}^{\mathit{Grace}}$ , are compared for their capability to match experimental gas hold-up. Numerical results of Reynolds-averaged Navier-Stokes equations with k-𝜀 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 ( $4⩽\mathit{p}⩽-0.5$ ), turning down that the best computed hold-up is within 0.44% for $\mathit{p}=0.5$ .