Thermal Chaotic Mixing of Power-Law Fluids in a Mixer with Alternately-Rotating Walls

TL;DR

This study explores how chaotic mixing techniques improve heat transfer in a two-rod mixer handling highly-viscous, non-Newtonian fluids, showing significant benefits for shear-thickening fluids through enhanced thermal homogenization.

Contribution

It demonstrates the effectiveness of chaotic mixing protocols in enhancing heat transfer for shear-thickening fluids in a specific mixer configuration.

Findings

Chaotic mixing improves thermal homogenization for shear-thickening fluids.

Chaotic protocols lead to increased apparent viscosity near walls.

Enhanced heat transfer observed in shear-thickening fluids with chaotic stirring.

Abstract

We investigate the enhancement of both mixing and heat transfer in a two-rod mixer for highly-viscous non-Newtonian fluids. The mixer is composed of two vertical, circular rods in a cylindrical tank. Chaotic flows are obtained by imposing the temporal modulations of the rotational velocities of the walls. We study the effects of different stirring protocols, which lead to non-chaotic and chaotic flows, on the efficiency of both mixing and heat transfer for three different rheological fluid behaviors: shear-thinning, Newtonian and shear-thickening. For this purpose, we use statistical indicators that characterize the mean value of the fluid temperature and its homogenization. We find that chaotic mixing is suitable for shear-thickening fluids for which we observe a clear enhancement of the thermal mixing (heat extraction and homogenization). This is due to the increase in the apparent fluid viscosity in the vicinity of the rotating walls. This aspect confirms the relevance of chaotic mixing for highly-viscous fluids.