Insights into the rheological behavior of ethanol-based metal oxide nanofluids

Abstract

Up to now, most of studies mainly focused on the heat transfer properties of the nanofluids, while there are very few works focusing on their rheological behavior which, however, is very crucial for the practical application of nanofluid regarding its efficient and low-cost transportation. In this work, rheological behavior of ethanol based nanofluids containing three kinds of metal oxide nanoparticles up to 0.15%wt were systematically investigated. All the ethanol-based metal oxide nanofluids were found to show the nonnewtonian behavior over a shear rate range of 50–350 s−1 at 5–20 °C. The shear stress and viscosity depend strongly on the temperature and shear rate and the temperature increase was found to lead to a sharp increase of viscosity-shear rate curve. It turned out that the concentration of nanoparticles only has the obvious effect on the viscosity rather than shear stress of the nanofluids. A higher nanoparticle concentration can reduce the viscosity but there is little difference for the rheology behavior over the investigated different types of nanoparticles. Our experimental results were found to fit well with Einstein's, Brinkman's, Batchelor's and Wang et al.'s models, which means the four models are valid in this situation. The Power law model were proves to fit the experimental results for the oxide nanofluids quite well.