Laminar Mixing Performances of a Stirred Tank Equipped with Helical Ribbon Agitator Subjected to Steady and Unsteady Rotational Speed

• Published in: Chemical engineering research & design 2002, Vol.80 (4), p.335-344
• Main Authors: Dieulot, J.-Y., Delaplace, G., Guerin, R., Brienne, J.-P., Leuliet, J.-C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical and Process Engineering; Chemical engineering; Engineering Sciences; Exact sciences and technology; Food engineering; helical ribbon impeller; Life Sciences; Mixing; Newtonian; unsteady stirring
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1205/026387602317446371

This paper investigates the way of improving the mixing of highly viscous Newtonian fluids in a tank using suitable operating conditions (unsteady stirring approaches). The agitator used is a non standard helical ribbon impeller fitted with an anchor at the bottom. The degree of homogeneity in the tank is followed using a conductivity method after a tracer injection. It is shown that the use of time-dependent rotational speed during the mixing process allows energy savings. For the unsteady stirring approaches tested, energy savings can reach up to 60% compared to the energy required to obtain the same mixing time with constant impeller rotational speed. Finally, a model is provided which allows the prediction of the mixing process of the agitated system with Newtonian fluids for both steady and unsteady stirring approaches.