Enhancement of laminar mixing in stirred vessel using geometrical perturbations

Abstract

Geometrical perturbations by using single and coaxial impellers configurations have been investigated in the laminar regime (Re = 2.68) in unbaffled stirred vessels. Combinations of one and two coaxial radial discharge flow impellers under centered and eccentric conditions were studied with viscous Newtonian fluid. The study of geometrical perturbations has been made in terms of the mixing times, energy consumption and the flow fields. Homogenization degrees and mixing times, determined with a color-discoloration technique, were evaluated by means of image processing. The flow fields were investigated using the particle image velocimetry technique. The use of off-centered impellers increases the pumping capacity; however, little effect of eccentricity was obtained when using two coaxial impellers under off-centered conditions obtaining the best results with a novel configuration consisting of a dual turbine with connecting plates.