Effect of surface wettability in condenser section on the thermo-hydraulic performance of a single-loop pulsating heat pipe: experiment study

The study fabricated the tubular pulsating heat pipes (PHPs) with different surface wettability characteristics in the condenser section using the electrochemical anodization and copper-based self-assembly methods. The thermo-hydraulic characteristics of PHPs with different surface wettabilities (neutral, hydrophobic, super-hydrophilic, and hybrid surface) in the condenser section were experimentally investigated under different heating powers and liquid filling ratios. The results showed that at different heating powers, the PHPs can achieve the optimal heat transfer performance at 50% filling ratio. As the heating power increases, the thermal resistance shows a gradually decreasing tendency, and the liquid plug spreads more easily on the super-hydrophilic condensation surface, and the temperature fluctuation is smoother with a thermal resistance lower than that of neutral PHPs. The liquid plug in the hydrophobic condensation surface has less contact with the wall, and the evaporation section presents a higher temperature and the thermal resistance is higher than that of neutral PHP. The PHPs with hybrid surface wettability exhibits a high-frequency oscillation and has more efficient thermal performance than the super-hydrophilic condensation surface PHPs, with the minimum thermal resistance at 50% filling ratio and 32.04 W heating power.