Effect of an Anchor Geometry on the Hydrodynamic Characteristics of a Nanofluid in Agitated Tank

Abstract

In this paper, the flow of a shear thinning nanofluid in a mechanically stirred tank has been numerically analyzed. This tank is cylindrical with a flat bottom. It is filled with Al2O3 nanoparticles suspended in the base fluid and equipped with an anchor-type stirrer whose shape is tilted upwards at an angle α. The purpose of this research is to study the impact of the tilt angle (0≤α≤π/6) and the effect of the alumina nanoparticles concentration (0≤φ≤0.1) on the hydrodynamic behavior and energy consumption. In the new anchor design (α>0), the fluid volume that is swept during the rotation of the anchor is the same as that in the case of a standard anchor (α=0). The laminar flow of the nanofluid is governed by the continuity and momentum equations taking into account the physical properties of the nanofluid introduced through correlations cited in the literature. The results obtained have shown that the tilt angle significantly contributes to the reduction of the power number, and leads to a decrease in the intensity of the tangential flow at the level of the extreme transverse planes of the tank. However, this reduction in intensity is compensated by increasing the axial flow. The use of nanoparticles in this work aims to show the role of the new design of anchor in creating a vortex at the bottom of the tank and to avoid of particles sedimentation.