Viscosity studies on novel copper oxide–coconut oil nanofluid

Novel coconut oil based copper oxide nanofluids of various concentrations have been prepared by ultrasonically assisted two step method. Viscosity studies have been made experimentally and theoretically at various temperatures and shear rates for different concentrations of nanofluid ranging from 0% to 2.5%. Shear thinning, a non-Newtonian behavior is observed in all the samples. The shear thinning is higher at lower shear rates and higher concentrations. The shear thinning at low concentration is attributed to the non-Newtonian behavior of carrier liquid, but at higher concentration there is a considerable contribution from particle too. The measured viscosities of nanofluids are compared with existing theoretical models and found to have very slight deviation due to size, morphology and interactions. New empirical correlations are proposed for predicting viscosity of CuO–coconut oil nanofluid at various temperatures and concentrations.

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► CuO–coconut oil nanofluids of various concentrations are synthesized.
► Rheological properties have been studied at various temperatures and shear rates.
► Reasons for non-Newtonian behavior are discussed.
► The measured viscosity is found to agree well with existing theoretical models.
► New correlations of viscosity with concentration and temperature are proposed.