Hydrothermally Synthesis of Al2O3 Nanoparticles for Nanofluids with Enhanced Critical Heat Flux

Water is widely used as a heat carrier in various devices such as automotive and nuclear reactors. Because of its better thermal characteristics, currently nanofluid is a candidate for replacing water and other conventional cooling fluids such as ethylene glycol and oil as a heat carrier. In this study, Al2O3 nanoparticles have been synthesized by the hydrothermal method for heat transfer nanofluid as an alternative to the new cooling fluid. Nanoparticles were synthesized using AlCl3 as a precursor, and urea was used as a capping agent. The hydrothermal process was carried out at 175°C for 17 hours. The hydrothermal product was dried and then calcined at 500°C for 1 hour. The resulting Al2O3 nanoparticles were analyzed using XRD, FTIR, and TEM. Nanofluids were prepared from these nanoparticles by dispersing them into the water as a base fluid. Nanofluid characterization was carried out through Critical Heat Flux (CHF) measurements. According to the XRD data, the Al2O3 nanoparticles produced were gamma-alumina with a crystallite size of 4 nm. The BET specific surface area was 302 m2/g. From the TEM image, it was known that the nanoparticles formed a cluster of rod-shaped particles. FTIR data shows the presence of OH groups on the surface of the nanoparticles. The Al2O3 nanofluids made were known to be stable with an average zeta potential of 54 mV. Compared to water, the CHF enhancement of this nanofluid increased by 111%. The nanofluid has the potential to be used as a cooling fluid for ECCS, RVCS, refrigeration, and metal machining process.