Design and performance evaluation of pulsating heat pipe using metallic nanoparticles based hybrid nanofluids

Abstract

Pulsating heat pipes (PHP) use two-phase flows to transport heat between evaporators and condensers. The performance of PHP largely depends on the thermal conductivity of the working fluid. The research objective of this study is to investigate PHP performance enhancement with HNF consisting of metallic and metallic oxide nanoparticles and compare the PHP performance with different working fluids. A three-turn PHP made from copper tubing was fabricated and charged with Al2O3-Cu HNF, Al2O3 mono nanofluid, Cu mono nanofluid, and pure water for performance evaluation. A total of ninety-eight (98) experiments were conducted with four working fluids over a range of operating conditions, including nanoparticles weight concentration (0.1 % and 0.2 %), filling ratio (50 % and 60 %) and heat input (30–90 W). Results showed that the Al2O3-Cu HNF achieved 30–54 % lower thermal resistance than water, and 17–43 % lower than the mono nanofluids at the same filling ratio, weight concentration and heat input, which indicates superior heat transfer enhancement. The optimal condition for the PHP filled with Al2O3-Cu HNF examined in this study was achieved at a 60 % filling ratio and a 0.2 % weight concentration of nanoparticles. However, maintaining the stability of Al2O3-Cu HNF poses challenges due to the hydrophobic nature of Cu nanoparticles. Future studies are planned to use molecular dynamics simulation to investigate factors influencing the stability of metallic nanoparticles-based mono and hybrid nanofluids.