HEAT TRANSFER CHARACTERISTICS AND FLOW CHARACTERISTICS OF Al2O3-CuO/WATER HYBRID NANOFLUIDS IN A HEXAGONAL SERPENTINE MICROCHANNEL

This study experimentally focuses on the flow and heat transfer characteristics of hybrid nanofluids in a hexagonal serpentine microchannel. The coolants such as hybrid nanofluid (Al<sub>2</sub>O<sub>3</sub>-CuO/water), nanofluids (Al<sub>2</sub>O<sub>3</sub>/water and CuO/water), and water were prepared with nanoparticles of Al<sub>2</sub>O<sub>3</sub> and CuO having volume proportion of 0.25% each. A serpentine microchannel with a side of 0.9 mm having hexagonal and square cross sections was used. The heat and flow characteristics such as Nusselt number, heat transfer rate, thermal resistance, pressure drop, pumping power, and friction factor were studied for the aforementioned cooling fluids and cross sections. The results reveal that the Al<sub>2</sub>O<sub>3</sub>-CuO/water hybrid nanofluid has enhanced heat transfer rate and pressure drop in a hexagonal serpentine compared with a square serpentine microchannel. The use of hybrid nanofluid enhances heat transfer rate, Nusselt number, and pressure drop up to 43.24%, 36.8%, and 30.53%, respectively, when compared with water. Also, the hexagonal serpentine microchannel creates a reasonable fall in thermal resistance and rise in pumping power than the microchannel with a square cross section used.