FLUCTUATION VELOCITY FOR NONNEWTONIAN LIQUIDS IN MIXING TANK BY RUSHTON TURBINE IN THE TRANSITION REGION

The hydrodynamics of the flow in stirred-tank reactors, i. e. velocity profiles, stress fields, turbulence characteristics and so on, are essential for the confident design of mixing tanks. Fluctuation tangential and radial velocities were measured using a twocomponent Laser Doppler Anemometry (LDA) system for a typical Rushton turbine impeller. The working fluids were different concentrations of polyacrylamide (PAA) solutions with rheological properties typical of those found in polymer processes. It is shown that the correlations for fluctuating velocities in Newtonian fluids do not apply to the case of viscoelastic liquids. New correlations are given in the lower part of the transition region, i. e. 30< Re< 2000, for fluctuating tangential and radial velocity components values along the center line of the impeller tip.

Keywords:

fluctuation velocity , LDA , Rushton turbine , viscoelastic , mixing