Experimental investigation of a novel heat exchanger for optimizing heat transfer performance using Al2O3-water nanofluids

This study presents an experimental investigation to determine the heat transfer enhancement in a novel heat exchanger known as the "Helicoidal Square-Shaped Heat Exchanger" with and without using a nanofluid. The experiments were performed for the range of Reynolds numbers from 4400 to 8000, using nanofluid (Al2O3-pure water) at the concentrations 0.1, 0.25, and 0.5%. This experimental investigation found that the heat transfer ratio is improved by increasing the nanofluid concentrations and the flow Reynolds number. The highest value of the heat transfer ratio was at Re = 8000, and 0.5% concentration of nanofluids. The corresponding increment in the heat transfer rate was 13.46 %, the heat transfer coefficient augmented by 9.64 %, and the Nusselt number improved by 10.43% compared to the results obtained experimentally with distilled water. The results obtained for the distilled water were verified with the Dittus-Boelter equation and numerical simulation. In addition, all obtained experimental data were compared with the CFD simulation. The use of nanofluids for heat transfer enhancement has a wide range of applications. Therefore, the presented results suggest using Al2O3-water nanofluids to improve the efficiency of many renewable energy plants, including solar and geothermal energy systems.