Optimizing stability and enhancing flow boiling heat transfer performance of Al2O3-TiO2/water hybrid nanofluids

Abstract

This study investigates the impact of stability on the flow boiling heat transfer performance of hybrid nanofluids comprising Al2O3-TiO2 nanoparticles dispersed in water, referred to as Al2O3-TiO2/W. The stability optimization of the Al2O3-TiO2/W hybrid nanofluid was carried out using the response surface methodology (RSM). Additionally, the boiling heat transfer performance of the Al2O3-TiO2/W hybrid nanofluid, along with its mono nanofluids (0.01, 0.02, and 0.03 vol%), was examined within a flow rate range of 30–90 L/h. The results revealed that the optimal stability of the initially prepared hybrid nanofluids was achieved with a surfactant SDS mass ratio of 0.554 and an ultrasonic time of 44.79 min. Furthermore, as the flow rate increased, the boiling heat transfer coefficient (h) exhibited an increasing trend followed by a decrease, reaching its maximum at 70 L/h. The h value also increased with higher heat flux and volume fraction. Compared to pure water, the Al2O3-TiO2/W hybrid nanofluid (0.03 vol%) exhibited a maximum enhancement of 61.9 % in h at a heat flux of 93.4 kW/m2. Moreover, the h of the Al2O3-TiO2/W hybrid nanofluid demonstrated an average enhancement of 6.4 % compared to its TiO2/W mono nanofluid counterpart. Additionally, the nano-influence factor (Fenh) displayed a pattern of increase followed by a decrease with the rise in flow rate, reaching its peak value of 1.62 at 40 L/h. Lastly, the thermal conductivity of the hybrid nanofluids exhibited a significant influence on the boiling heat transfer performance, showing a strong linear correlation coefficient (r) of 0.943. This correlation suggests a strong relationship between thermal conductivity and boiling heat transfer performance.