Ultrasonic assisted new Al_2O_3@TiO_2-ZnO/DW ternary composites nanofluids for enhanced energy transportation in a closed horizontal circular flow passage

摘要

Experiments were conducted to study the turbulent heat transfer growth of single pot sonochemically assisted new Al_2O_3@TiO_2-ZnO/DW based ternary composite nanofluids in a closed circular heat exchanger under constant heat flux boundary conditions. The two-step facile nanofluid preparation approach was used to prepare the new ternary hybrid nanofluids. The UV-Vis and FESEM analysis were performed to confirm the absorbance and uniform dispersion of all nanoparticles. Under uniform heat flux conditions, Al_2O_3@TiO_2-ZnO/DW based ternary composite nanofluids at 0.1, 0.075, 0.05, and 0.025 wt% reveals positive growth in heat transfer coefficient (h) and Nusselt numbers (Nu) with an increase in Reynolds (Re) number from 5849 to 24,544 without using any surfactant. The maximum increase in effective thermal conductivity was recorded up to 1.14 W/m.K for Al_2O_3@TiO_2-ZnO/DW ternary composite nanofluids with 0.1 wt% at 45 °C, which increases by 69% compared to the base fluid. The overall average and local heat transfer/Nusselt numbers were noticed to improve with an increase in wt% of all metal oxide nanoparticles and Reynolds numbers (Re) under constant heat flux conditions in the circular heat exchanger. The highest heat transfer coefficient was recorded for Al_2O_3@TiO_2-ZnO/DW ternary composite nanofluids at 0.1 wt% up to 3200 W/m~2K for the highest Reynold (Re) numbers, which increases by 79% compared to the base fluid (DW). At 0.075 wt% the heat transfer enhancement was 2272 W/m~2K, similarly, at 0.05 wt% the heat transfer was 2150 W/m~2K while at 0.025 wt% the enhancement was 1950 W/m~2K which is more than base fluid (DW). This enhancement is credited to the composite of nanoparticles with different shapes and particle sizes. The experimental results showed that the metal oxide-based new ternary composites nanofluids enhanced the thermophysical and heat transfer properties, hence, it is a suitable choice for enhanced energy transportation.