One-pot sonochemical synthesis route for the synthesis of ZnO@TiO2/DW hybrid/composite nanofluid for enhancement of heat transfer in a square heat exchanger

The thermophysical properties of ZnO@TiO 2 /DW composite nanofluids with (0.1, 0.075, 0.05 and 0.025)mass% concentrations have been experimentally studied. The equal and homogenous dispersion of both ZnO and TiO 2 nanoparticles with 50:50 ratio each in distilled water (DW) was attained by the sonochemical method. The efforts are directed to examine the effective thermal conductivity of the different mass% concentrations of ZnO@TiO 2 /DW composite nanofluid for a selected range of temperatures at 20 to 45 °C. The maximum improvement in thermal conductivity for ZnO@TiO 2 /DW composite nanofluid was noticed for 0.1 mass% concentration, and the maximum enhancement was spotted 47% higher than the base fluid (DW). The heat transfer properties of ZnO@TiO 2 /DW composite nanofluids with (0.1, 0.075, 0.05 and 0.025) mass% concentrations and base fluid (DW) in a square heat exchanger were also investigated. Average and local heat transfer values and growth in Nusselt values were conquered for different velocities and corresponding to specific Reynolds numbers range from 4550 to 20,360. The maximum improvement increases about 57% in average heat transfer (h) and Nusselt numbers correspondingly, while local heat transfer for 0.1 mass% is about 500 to 1750 W m −2 K, for 0.075 mass% is 500 to 1500 W m −2 K, for 0.05 mass% is 500 to 1370 and for 0.025 mass% is 500 to 1150 of the composite nanofluid which is greater than base fluid (DW). The ZnO and TiO 2 mixture gives the best combination to enhance the overall heat transfer coefficient (h). Graphic abstract