Effect of TiO2-Al2O3 nanoparticle mixing ratio on the thermal conductivity, rheological properties, and dynamic viscosity of water-based hybrid nanofluid

Abstract

Many researchers in the past decade have focused on the influence of nanoparticle volume concentration on the thermophysical properties of hybrid nanofluid. However, less research is available on the effect of the mixture composition between two different nanoparticles to the thermophysical properties of the fluid. This study means to research the influence of TiO2-Al2O3 nanoparticle mixing ratio on the thermal conductivity, rheological properties and dynamic viscosity of water-based hybrid nanofluid. The water-based hybrid nanofluid was prepared using five different proportion of TiO2 and Al2O3 nanoparticles at a fixed 1.0% volume concentration. The temperature range selected for the experimental test procedure is between 30−70 °C. The mean crystallite size of TiO2 and Al2O3 nanoparticles calculated using the results from XRD characterization is about 19.1 and 8.31 nm, respectively. The highest thermal conductivity value of 1.134 W/m K is observed for hybrid nanofluid with the nanoparticle mixing ratio of 50:50 at 70 °C, with an average thermal conductivity augmentation of 71% comparative to deionized (DI) water. The developed hybrid nanofluid found to exhibit Newtonian flow behaviour at all nanoparticle mixing ratios and temperature. Moreover, the hybrid nanofluid with 80:20 ratio recorded the highest dynamic viscosity of 1.98 mpa s. Besides, the prepared hybrid nanofluid was found to achieve moderate stability with zeta potential value of 29.6 mV. Finally, two different correlation model was developed using regression analysis to predict the thermal conductivity and relative dynamic viscosity for various TiO2-Al2O3 water-based hybrid nanofluid.