Stability, surface tension, and thermal conductivity of Al2O3/water nanofluids according to different types of alcohol and their proportion

In this study, the stability, surface tension, and thermal conductivity of Al2O3/water nanofluids with different types of alcohol fluids were investigated. Different types of alcohols (butanol, pentanol, and hexanol) were added to the Al2O3/water nanofluid. From the UV–vis spectroscopy results, Al2O3/water nanofluids did not show a significant absorbance difference for concentrations more than 0.5 wt%. From 0.1 to 0.5 wt% the absorbance enhancement ratio was 101.3%; however, it was 9.0% from 0.5 to 0.9 wt%. Therefore, 0.5 wt% Al2O3 nanofluids are effective in terms of fluid dispersibility. During the zeta potential measurement of the nanofluid stability, increasing the Al2O3 in the nanofluids caused more instability. However, the type and concentration of the aqueous alcohol solutions without Al2O3 did not significantly affect the stability characteristics. The contact angle of the alcohol-based nanofluids at saturated concentrations showed a decrease of at least 18.7%. Adding Al2O3 nanoparticles to the alcohol-based nanofluids increased the surface tension by an average of 3.4%. The thermal conductivity of the alcohol-based nanofluids was lower than that of distilled water. However, the addition of Al2O3 can enhance their thermal conductivity. The thermal conductivity lowered by the alcohol-based fluids enhanced by an average of 73.4% after adding Al2O3.