Rheology of methanol-based metal oxide nanofluids: Effects of temperature, particle type, and mass fraction

Viscosity and shear stress are the important rheological properties for nanofluids as they significantly affect the flow and heat transfer process. The rheology of the water-based nanofluid has been well studied, although the results are scarce for non-aqueous nanofluids. This study reports the rheology properties of three different oxide nanofluids (Cu₂O, CuO, and TiO₂) in methanol, a typical non-aqueous base liquid, at different mass fractions and temperatures. The methanol-based oxide nanofluids behaved as non-Newtonian fluids with a shear shining phenomenon. The effect of high temperature on rheology resulted in low viscosity and shear stress. The higher the temperature, the lower the viscosity and shear stress. The particle type caused increase of both shear stress and viscosity, with a decreasing order of CuO > Cu₂O > TiO₂. Our experimental results were then fitted and compared to various empirical models. The Ostwald-de-Waele correlation fit our experimental results for three different kinds of oxide nanofluids quite well, especially for TiO₂.