Simulation of the Mixing of Highly Viscous Fluids with a Scaba 6SRGT Impeller Using CFD

摘要

Mixing is among the most common processes in chemical, biochemical, pharmaceutical, polymer, mineral, food, and wastewater treatment industries. Understanding mixing mechanisms, which is crucial to industrial scale-up, still remains difficult especially in the case of non-Newtonian fluids. Shear-thinning fluids with yield stress are an important class of non-Newtonian fluids, which are commonly encountered in industrial mixing operations. Mixing of such fluids results in the formation of a well mixed region (the so called cavern) around the impeller and essentially stagnant and/or slow moving fluids elsewhere in the vessel. The general practice for the evaluation of stirred tanks has been done over the years through the experimental investigation for a number of different impellers, vessel geometries, and fluid rheology [1-4]. Such an approach is usually costly and sometimes is not an easy task. With computational fluid dynamics (CFD), we can examine various parameters contributing in the process in shorter time and with less expense [5], a task otherwise difficult in experimental techniques. The objective of the present paper is to use CFD to model the flow field generated by a Scaba 6SRGT impeller in the mixing of shear-thinning fluids with yield stress.