Abstract
The attention of researches in convective heat transfer by suspended nanoparticles in base fluids has grown lately to promote uncommon techniques for enhancing the thermal performance of fluids. In this study, the stability period and thermal properties of aluminium oxide (Al2O3), silicon dioxide (SiO2) and Al2O3–SiO2 hybrid were investigated at volume concentration 0.1vol.% dispersed in Distilled Water (DW) as a base fluid. For the hybrid nanofluid, the samples were consisted of (0.025 vol.%Al2O3+0.075vol.%SiO2),(0.05vol.%Al2O3+0.05vol.%SiO2)and(0.075vol.%Al2O3+0.025vol.%SiO2). The two-step method was adopted to prepare the nanofluid samples by using Ultrasonic device. Three different ultrasonication times were fitted for preparing the samples (1hr,2 hr and 3 hr).The properties of single and hybrid nanofluids were evaluated at various temperatures (from 30 °C to 70 °C). The obtained results demonstrated that the dispersion of nanoparticles was homogeneous and more stable for a longer period for all samples that prepared at 3 hr of ultrasonication process. Among all samples of nanofluids, SiO2/DW was found to be the most stable coolant. For all nanofluids, with an increase of temperature, the thermal conductivity and specific heat were increased significantly while density and viscosity were decreased.
