Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part I: Basis of The Model

Abstract

Mixing processes with different stirring systems in agitated vessels are simulated by a multi-region model. Because of discontinuities at the boundaries of different regions appearing for the already-existing simple three-region model, unrealistic values occur during the calculation of the concentration distribution at these locations. Therefore, the region model will be modified at first. The procedure is presented here for the example of a radial flow stirrer, considering the fluid velocity, the turbulence field, the particle diffusion, and the relative fluid-to-particle velocity. The modified model is discussed and validated. Thus, the behavior of single particles and particle swarms can be analyzed in the vessel considering different aspects.

Simplified Calculation of Mixing and Suspending Processes in Agitated Vessels – Part II: Examples of Application

“…The calculation of hydrodynamics in mixing vessels has been discussed in Part 1 of this work [1]. Three cases are now demonstrated here and are summarized in Tab.…”

“…2. However, as already discussed for the example of the radial flow impeller in Part 1 of this work [1], it is possible to connect both models using an advanced velocity model. However, these connections are not applied for the calculation of the axial flow impeller presented here.…”

“…Particles may also accumulate in a cell, especially in areas with decelerating transport of particles. This enrichment of particles can only be reduced at the diffusion step (see [1]), which takes a long time, especially in areas with low fluid turbulence. This effect becomes more obvious from the 3D-plot in Fig.…”

“…Figs. 1-4 show the distributions of the radial, axial, and tangential velocity components and of the turbulent diffusion coefficients based on the models presented earlier [1] and [2].…”

“…The tangential velocity at the exterior of the stirrer jet stream does not depend on the axial direction for the unbaffled case b and for the calculation model used here 1) . The model results in a tangential velocity being totally locally independent for the cases c 1 and c 2 , Fig.…”