An experimental study on rheological behavior of hybrid nanofluids made of iron and copper oxide in a binary mixture of water and ethylene glycol: Non-Newtonian behavior

This paper includes an experimental study on rheological behavior of hybrid nanofluids made of iron (Fe) and copper oxide (CuO) in a binary mixture of water and ethylene glycol. Nanofluid samples, with solid volume fractions of 0.05, 0.1, 0.25, 0.5, 1 and 1.5%, were prepared by dispersing an equal volumes of Fe and CuO nanoparticles in a binary mixture of water and ethylene glycol with the proportion of 20-80 vol. %. Viscosity measurements were performed at temperatures ranging from 25 degrees C to 50 degrees C and the shear rate range of 3.669-122.3 s(-1) for all samples. Experimental findings revealed that the low concentration samples showed Newtonian behavior, while the high concentration samples had non-Newtonian behavior and followed the power law model. Moreover, the power law index and consistency index were obtained using curve-fitting on experimental shear stress-shear rate dependency. The curve-fitting results revealed that the power law index reduced to 0.36, indicating that the high concentration samples possessed shear-thinning behavior at all temperature considered. (C) 2016 Elsevier Inc. All rights reserved.