Experimental and CFD studies of power consumption in the agitation of highly viscous shear thinning fluids

Abstract

Mixing of non-Newtonian fluids is widely encountered in the process industries. In this research, we obtained a constitutive expression that relates the viscosity of a mixture of glycerol and a gel formed of polyethylene glycol and Carbomer to the shear rate, temperature and mass fraction of one of the two components. We found that the mixtures of these two fluids were well characterized by a non-Newtonian power law model. We then used a number of homogeneous mixtures of the two fluids at different temperatures and mass fractions in a simple stirred tank agitated mechanically by a Rushton turbine to derive experimental power curves, which we then derived numerically in a CFD model by replicating the experimental conditions. We used a combination of an air bearing and a load cell to precisely measure the power required by the impeller to agitate the non-Newtonian mixtures. The computational and experimental results are in good agreement, indicating that the rheological data and the CFD model are accurate.