An Experimental Study on SiO2-ND Hybrid Nanofluid: Thermal Conductivity, Viscosity, and Stability with New Forecast Models

Objective: In the present investigation, thermal conductivity and viscosity properties of water-based SiO2-ND hybrid nanofluid were measured, experimentally. Methods: Nanofluids were prepared by using a two-step method and with three different (0.5%, 0.75%, and 1%) concentrations. Every concentration had three different SiO2-ND mixtures (50% SiO2 - 50% ND, 33% SiO2 - 66% ND, 66% SiO2 - 33% ND). Results: The most stable sample was measured as -33.4 mV. Measurements of viscosity and thermal conductivity were done from 20°C to 60°C at every 10°C. Thermal conductivity data were measured by thermal conductivity analyzer and viscosity data were measured by tube viscometer. The highest thermal conductivity enhancement was measured for 1% SiO2^0.33: ND ^0.66 at 40°C and the highest relative dynamic viscosity was calculated as 4.19 for 1% SiO2^0.33: ND ^0.66 at 40°C. A comparison table is also given to show the zeta potential values-concentration relations. Conclusion: Finally, two different correlations for predicting thermal conductivity and viscosity were proposed for practical usage.