Hydrodynamics performance of Newtonian and shear-thinning fluids in a tank stirred with a high shear impeller: Effect of liquid height and off-bottom clearance

Abstract

The hydrodynamics performance of a ring-style Hockmeyer© high-shear impeller (HSI) in an unbaffled tank with Newtonian and shear-thinning fluids at Reynolds numbers (Re) between 20 and 300 is addressed. Power measurements of this study were used to validate computational fluid dynamics simulations. Key hydrodynamic parameters for the HSIs performance, i.e., pumping and power numbers, and viscous dissipation are analyzed. The effect of the off-bottom clearance (C), working fluid height (Z) (in the range 0.18 ≤C/T ≤ 0.38 and 0.8 ≤Z/T ≤ 1, where T is the tank diameter), and fluid rheology, on these parameters were investigated. Results show that the examined C/T and Z/T ratios do not significantly affect the power number. The fluid rheology, C/T and Z/T had, on the contrary, a significant impact on the remaining hydrodynamic parameters. For 45 ≤Re≤ 300, the shear-thinning fluid showed better performance for dispersion processes, i.e., higher pumping number and viscous dissipation, and lower power number than the Newtonian fluid.