Effect of nanofluids-PCM heat exchanging on engine downsizing and heat transfer enhancement via the heat engine's cooling system: A novel saving tactic

This study presents a novel heat transfer system that utilizes water/nanofluids and phase change materials (PCM) for enhanced thermal energy storage and management. The hybrid system stores heat energy in the PCM, releasing it into the airflow through heat exchange, without mixing materials. Experiments involved water-based nanofluids with TiO₂ and Al₂O₃ nanoparticles at concentrations of 0.08 % and 0.16 %, combined with PCMs. Variables included flow rates (1.28 to 5.18 L/min) and fan speeds (1000 to 2200 rpm), assessing their effects on the convective heat transfer coefficient. Results demonstrate that combining nanofluids with PCMs significantly boosts efficiency in cooling and storage systems, allowing for smaller engine size and lower energy use at high flow rates and fan speeds. The addition of 0.08 % TiO₂ nanoparticles increased the heat transfer coefficient by up to 21 %, while incorporating PCM boosted it by 39 %. With 0.16 % TiO₂, heat transfer improved by 65 %, and PCM further increased it by 2.5 times. Al₂O₃ nanofluids also showed a 37 % improvement at 0.08 %, surpassing TiO₂, and reached a 2.3-fold enhancement at 0.16 % with PCM. These results underscore the potential of nanofluid and PCM combinations for efficient, compact, and energy-saving thermal systems.