Sustainable Thermal Performance Analysis of a Pulsating Heat Pipe Using Zinc Oxide-ethanol Nanofluid

Enhancing heat transfer efficiency is critical for sustainable thermal management in modern applications such as electronics cooling, solar thermal systems, and waste heat recovery. This study investigates the thermal performance of a pulsating heat pipe (PHP) using zinc oxide (ZnO)-ethanol nanofluid, with the aim of developing an environmentally friendly and energy-efficient heat transfer system. Experiments were conducted using both base fluid (ethanol) and ZnO-ethanol nanofluid under identical conditions to assess the effects of filling ratio, inclination angle, and nanoparticle concentration. The experimental setup involved the fabrication of a PHP with three loops (6.5 mm internal diameter, 1.5 mm wall thickness), subjected to thermal tests at 30% filling ratio. Nano fluid preparation included magnetic stirring and ultrasonic homogenization of ZnO nanoparticles in ethanol at 1 wt% concentration. Results reveal a 16% enhancement in effective thermal conductivity with the ZnO-ethanol nanofluid compared to ethanol alone. Optimum performance was observed at a 50% filling ratio and 30° inclination angle. Additionally, the ZnO nanofluid showed higher heat rejection and stability of 42 days. The study highlights the superior thermal efficiency and sustainability potential of ZnO-ethanol nanofluids in passive thermal management.