Effect of internals on the flow pattern and mixing in stirred tanks

The flow pattern, power consumption, and mixing time in a stirred vessel depend not only on the impeller design but also on the tank geometry and internals. Measurements of power consumption, mixing time, and flow pattern have been carried out in a stirred vessel of 0.5 m diameter for a standard 45 degrees pitched-blade turbine and for a hydrofoil impeller with a variety of baffle and draft tube configurations. The comparison of the flow pattern (average velocity, turbulent kinetic energy, maximum energy dissipation rate, average shear rate, and turbulent normal stress) has been presented on the basis of equal power consumption to illustrate the extent of interaction between the rotating impeller and the internals. Comparisons of laser Doppler anemometer (LDA) measurements and computational fluid dynamics (CFD) predictions have been presented.