In the thermal engineering applications, suspension of nanoparticles in conventional fluid has positive potential in enhancing the convective heat transfer performance. The evaluation of thermo-physical properties is essential to investigate the forced convection heat transfer of nanofluids. Hence, the present study reports the analysis on thermal conductivity and dynamic viscosity for Al2O3 nanoparticle dispersed in a different volume ratio of water (W) and ethylene glycol (EG) mixture. The Al2O3 nanofluids are formulated using the two-step method for three different base mixtures with volume ratio of 40:60, 50:50 and 60:40 (W:EG). The measurement of thermal conductivity and viscosity were performed using KD2 Pro Thermal Properties Analyzer and Brookfield LVDV-III Rheometer; respectively for temperature from 30 to 70 °C and volume concentration of 0.2-1.0%. The average thermal conductivity enhancement of Al2O3 nanofluids in the three base ratios varied from 2.6 to 12.8%. The nanofluids have better enhancement as the percentage of ethylene glycol increases. Meanwhile, the average dynamic viscosity enhanced up to 50% for 60:40 (W:EG). The enhancement of viscosity for nanofluids decreased with the increment percentage of ethylene glycol. The properties enhancement of the Al2O3 nanofluids is significantly influenced by the concentration, temperature, and based ratio.
Nanofluid as a coolant has potential for use in the heat transfer field because of its augmentation in thermal properties that offers advantages in heat transfer. Research on various working temperatures is still ongoing in the nanofluid field. This study focused on the effect of temperature on heat transfer behavior using titanium dioxide or TiO 2 nanofluid as the working fluid in forced convection. The heat transfer coefficient was determined for flow in a circular tube under constant heat flux boundary conditions. The experiment was conducted with a Reynolds number less than 25000 with concentrations of TiO 2 nanofluid at 0.5%, 1.0% and 1.5%. At 30 o C, the maximum enhancement of 9.72% for 1.5% volume concentration was observed. Enhancements of 22.75% and 28.92% were found at 50 o C and 70 o C, respectively under similar nanofluid concentrations. The nanofluid performance was significantly influenced by working temperature. The heat transfer enhancement of TiO 2 nanofluid was considerably improved at higher working temperature and high concentration because of the improvement of thermal properties.
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