Viscosity estimation of Al2O3, SiO2 nanofluids and their hybrid: An experimental study

Over the last years, tremendous efforts were dedicated to develop new heat transfer fluids. So, the research on this topic was later on focused on nanofluids, ionanofluids, molten salts and new refrigerants. This article explores two mono-component and one bi-component nanofluid and, to be more specific, it deals with the viscosity study of stabilized Al2O3, SiO2 water based nanofluids and their hybrid (Al2O3 + SiO2 nanoparticles diluted in water). Experimental research showed a non-Newtonian behavior of all tested nanofluids. Alumina nanofluids and the two studied hybrid nanofluids have shear-thinning behavior and silica nanofluid have a shear thickening behavior. More exactly, the overall relative viscosity is higher for alumina nanofluids if compared to SiO2 nanofluid and, by replacing 0.5% of SiO2 with alumina, the viscosity increases if compared to results for SiO2 nanofluid. Few correlations are proposed for a better estimation of the viscosity for Al2O3, SiO2 water based nanofluids. Plus, the viscosity variation with temperature was experimentally studied for the case of hybrid nanofluids, underlying the decreasing of viscosity while temperature rise and the low hysteresis behavior while proposing two equations for the viscosity variation as temperature was increasing.