CFD simulation of particle distribution in stirred vessels

In this work the particle concentration distribution in two-phase stirred t anks is simulated on the basis of information on the three-dimensional flow field, as obtained by numerical solution of the flow equations (CFD) using the well known k - epsilon turbulence model. Two modelling approaches are attempted. In the simpler method the dow field is first simulated neglecting the influence of the solid phase; on the bas is of the resulting flow field a very simple sedimentation model is employe d for solving the solids mass balance equations in order to compute the par ticle concentration field. In this case no inertial effects on the solid pa rticles are considered, so that the convective and diffusional exchanges fo r the solid phase are assumed to coincide with those for the liquid phase. In the more advanced approach the momentum balance equations for both the s olid and liquid phases are simultaneously solved. Experimental data on the axial profiles of particle concentration have been obtained in a laboratory scale agitated tank. The experimental technique u tilized is non intrusive being based on light attenuation measurements and is also able to provide information at high particle concentrations. The comparison of experimental data with simulation results is satisfactory with both simulation approaches. Differences between the two approaches co ncerning their accuracy and computational effort are discussed. The need to make a suitable estimate of the particle drag coefficients in turbulent fl uid media is emphasized.