Effect of nanoparticle mixture ratio on the thermophysical properties of TiO2 / Al O3

• Main Author: Shangkaran A/l Radakrishnan
• Published: 2023
• Subjects: Hybrid Nanofluid; Thermophysical Properties; Thermal Fluid

Development in engineering technology urging more efficient and productive systems to be enhanced especially thermal industry. Preparation and characterization of TiO2-Al2O3 hybrid nanofluid were focussed throughout this project which is relevant to heat transfer application. Five different mixture ratios (20:80, 40:60, 50:50, 60:40 and 80:20) of TiO2-Al2O3 hybrid nanoparticles were prepared via two-step methods which are magnetic stirring and ultrasonication. The volume concentration of the nanofluid was set constant throughout the study at 1% and Polyvinylpyrrolidone (PVP) used as a surfactant. Furthermore, pH measurements of TiO2-Al2O3 hybrid nanofluid were taken to study the influence of pH against the stability of the hybrid nanofluid. The range of pH is from 6.8 - 6.6. Next, the stability of hybrid nanofluid was visually observed after preparation and after 30 days. Sedimentation occurred after 30 days gradually increases from 20:80 to 80:20 mixing ratio of TiO2-Al2O3 nanoparticle. Measurement of stability was also conducted using zeta potential value. The obtained mean zeta potential is 24.6 mV. Besides, two major thermophysical properties were examined in this study which is thermal conductivity and dynamic viscosity. For both properties, testing conducted at a various temperature range from 30 oC to 70 oC at an increment of 10 oC. Thermal conductivity was measured using the KD2 Pro instrument where else dynamic viscosity was measured using Brookfield LVDV III Ultra Rheometer. Besides, the measurement from these instruments was also validated with sample pure water reference to the property table. Maximum thermal conductivity enhancement of 71% achieved at 70oC by 0.5 mixture ratio and minimum thermal conductivity enhancement of 0.7% achieved at 30oC by 0.8 mixture ratio. Relation of the effective thermal conductivity of TiO2-Al2O3 hybrid nanofluid increases when the temperature increases were observed. Moreover, the maximum dynamic viscosity enhancement of 232% achieved at 70oC by 0.8 mixture ratio and minimum dynamic viscosity enhancement of 121% achieved at 30oC by 0.4 mixture ratio. Relation of the relative dynamic viscosity of TiO2-Al2O3 hybrid nanofluid increases when the temperature increases were observed. Comparisons were made with other literature based on the effective thermal conductivity and relative dynamic viscosity. The overall patterns and trends are seemed similar among other studies which make this present study to significant and valid. The property enhancement ratio was also determined via the thermal conductivity and dynamic viscosity. Lastly, experimental data for thermal conductivity and dynamic viscosity of TiO2-Al2O3 hybrid nanofluid helps to develop a new regression correlation for both effective thermal conductivity and relative dynamic viscosity with the effect of temperature and nanoparticle mixture ratio.