New Chaotic Approach for Mixing Shear-Thinning Fluids in Stirred Tanks

The mixing of inelastic shear-thinning fluids has been investigated by using a chaotic approach. Two different scenarios based on single and dual off-centered impellers have been proposed and compared to the standard configuration (steady stirring) showing the potentialities and drawbacks of the proposed arrangements. Mixing times were evaluated by means of color-discoloration technique based on a fast acid-base indicator reaction. An aqueous solution of low concentrated purple bromocresol was used as tracer and added to the tank in the beginning of the experiments and then NaOH or HCl were added to the fluid to be tested in order to change its pH and as a consequence its color. It is demonstrated that, if the operating conditions of the proposed scenarios are properly set, the mixing times can be drastically reduced compared to those obtained under the standard configuration.