Experimental measurement of viscosity and electrical conductivity of water-based γ-Al2O3/MWCNT hybrid nanofluids with various particle mass ratios.

The hybridization of nanoparticles is a concept employed for the improvement of the thermal properties of nanofluids. Presently, there is a scarcity of studies in the open literature concerning the influence of particle mass ratios of hybrid nanofluids on the thermal properties. Thus, this paper investigated the effect of temperatures (15–55 °C) and particle mass ratios (90:10, 80:20, 60:40, 40:60, and 20:80) on the viscosity and electrical conductivity of deionized water (DIW)-based γ-Al2O3 and MWCNT hybrid nanofluids. A two-process strategy was deployed to prepare the hybrid nanofluids at a volume concentration of 0.1%. The hybrid nanofluids were characterized for their morphology using a transmission electron microscope. Hybrid nanofluid stability was monitored using UV visible spectrophotometer, viscosity, and visual inspection methods. The prepared nanofluids were observed to be stable with relatively constant viscosity and absorbance values. At 55 °C, maximum enhancements of 442.9% and 26.3%, and 288.0% and 19.3% were recorded for the electrical conductivity and viscosity of Al2O3–MWCNT/DIW nanofluids at particle mass ratios of 90:10 and 20:80, respectively, in relation to DIW. Temperature increase was observed to significantly reduce the viscosity of hybrid nanofluids while the particle mass ratio considerably and positively impacted the electrical conductivity. The relatively low viscosity of the hybrid nanofluids coupled with its reduction under increasing temperature and its insignificance increase as the particle mass ratio of the Al2O3 nanoparticles increased to make them viable coolants for engineering applications. New correlations were proposed to accurately estimate the viscosity and electrical conductivity of the hybrid nanofluids. [ABSTRACT FROM AUTHOR]