Document Type : Original Article
Department of Metallurgy and Mechanical Engineering, Technology and Engineering Research Center, Standard Research Institute (SRI), Karaj, Iran
A nanofluid is a fluid in which particles with a size between 1 and 100 nm are permanently suspended in the base fluid. The addition of nanoparticles affects the thermophysical properties of the liquid. In this study, the effect of temperature and concentration of alumina and titanium dioxide nanoparticles on the thermal conductivity and dynamic viscosity of a base fluid comprised of water and ethylene glycol was investigated. The volume fraction of the nanoparticles was 0.05, 0.1, 0.5, and 1 %vol. and the test temperatures were chosen to be between 260 and 305 K. SEM and TEM were used to examine the nanoparticles' morphology and microstructure. XRD analysis was used to detect phases in nanoparticles. BET analysis was also used to determine the specific area and porosity of the nanoparticles. The hybrid nanofluids' thermal conductivity and dynamic viscosity were measured and compared to the base fluid. The results showed that the thermal conductivity of the Al2O3-TiO2/ethylene glycol-water hybrid nanofluid depended on the concentration of nanoparticles and temperature. The findings revealed that the thermal conductivity of hybrid nanofluids increases with temperature and nano-additive concentration. Moreover, the viscosity increases with the increasing volume fraction of nanoparticles. As the results show, the viscosity changes with temperature are more pronounced at higher concentrations.