(126f) CFD Prediction of Liquid Homogenization with Variable Viscosity in a Stirred Tank

Mixing and dissolution processes are still an area of ongoing research. CFD has proven to be tool that can be used to understand and to optimize industrial mixing problems. For many applications CFD is well developed and validated but for more complex applications (e.g. industrial mixing) there is still much work to do until CFD will be an engineering tool providing reliable results in a sufficiently short calculation time.

In this contribution we focus on the mixing and dissolution of a bulk powder in a highly viscous solution in a stirred tank reactor. The effects of a variable viscosity (both in time and space) and the bulk powder addition on the mixing process efficiency and the power consumption are studied in detail. The time dependent and turbulent flow of the mixture is studied by using the code AVL FIRE. The non-constant viscous behavior was accounted for in a Reynolds averaged Navier-Stokes equations by the well-known Einstein formula for the viscosity of the suspension, while the concentration of a passive scalar is used as a measure for the volume fraction of the dissolving solid phase. In addition, the influence of different numerical approaches, i.e., the multiple reference frame and sliding mesh methods, are presented.