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RESEARCH PRODUCT

CFD Simulation of Particle Distribution in a Multiple-impeller High-Aspect-Ratio Stirred Vessel

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Publisher Summary This chapter describes fully predictive simulations of solid–liquid suspensions in a high-aspect-ratio, multiple-impeller stirred tank. These are performed by using the Inner Outer impeller modeling technique coupled with the Multi Fluid Model (MFM) for the treatment of the dispersed phase. The strongly simplified Settling Velocity Model (SVM) is also tested. The effects of free-stream turbulence on the drag coefficient CD and particle settling velocity are accounted for by means of a recently proposed correlation. Comparison of simulation results with experimental particle concentration profiles shows that the MFM approach leads to fair agreement with experimental data. Results obtained by the much simpler SVM are found to be in similar agreement with experiment, but at the cost of a much smaller computational effort. It is finally shown that one of the main sources of discrepancy between experiment and simulations lies in the underestimation of the pumped flow rate, a feature usually observed also in fully predictive single-phase simulations. This implies that improvements in the reliability of fully predictive two-phase simulation can be expected from advances in the single-phase simulation capability. Apart from that, the presently available two-phase models appear to be sufficiently accurate for engineering purposes, at least for the dilute two-phase systems.