Coaxial mixer hydrodynamics with Newtonian and non-Newtonian fluids

Abstract

The performance of several combinations of a wall scraping impeller and dispersing impellers in a coaxial mixer operated in counter- and co-rotating mode were assessed with Newtonian and non-Newtonian fluids. Using the power consumption and the mixing time as the efficiency criteria, impellers in co-rotating mode were found to be a better choice for Newtonian and non-Newtonian fluids. The hybrid impeller-anchor combination was found to be the most efficient for mixing in counter-rotating or co-rotating mode regardless of the fluid rheology. For both rotating modes, it was shown that the anchor speed does not have any effect on the power draw of the dispersing turbines. However, the impeller speed was shown to affect the anchor power consumption. The determination of the minimum agitation conditions to achieve the just suspended state of solid particles (Njs) was also determined. It was found that Njs had lower values with the impellers having the best axial pumping capabilities. © 2004 WILEY-VCH Verlag GmbH and Co.