Improved mixing of viscoelastic fluids by the use of hysteresis effect

Abstract

A non-conventional mixing strategy utilizing the hysteresis effect of propeller jets in viscoelastic xanthan gum solutions was evaluated through decolorization mixing time experiments. The experiments consisted of capturing and analyzing the images of the flow patterns illustrated by a fast acid-base indicator reaction in a rectangular tank equipped with a side-entering propeller. A non-subjective image processing method using average color was compared with the literature. The steady operation using the axial flow pattern was found more effective than the one using the semi-radial flow pattern. The time-periodic operations with appropriate combinations of both flow patterns significantly enhanced mixing, whereas an inappropriate combination extended the mixing time. The unsteady mixing concept using the hysteresis effect shortened the mixing time, even when the propeller was operated at a reduced rotational speed. Hence, the mixing strategy utilizing the hysteresis effect can reduce mixing time and power consumption simultaneously.