Abstract: The heat transfer performance of a C-shaped pulsating heat pipe(PHP)was experimentally investigated using acetone, absolute ethanol, deionized water, methanol, and an acetone-methanol mixture as working fluids. The experiments were conducted under varying heating powers(ranging from 30 W to 270 W)and filling ratios(ranging from 30% to 80%). The results indicated that within the experimental parameter range, the C-shaped PHP exhibited excellent flow pattern transition speed and startup performance when acetone and methanol were used as working fluids. The thermal resistance generally showed a decreasing trend with the increase in heating power; however, the improvement of thermal resistance by power increment exhibited a significant marginal effect. Thermal resistance demonstrated obvious filling ratio-dependent characteristics in different power intervals. Thus, the optimal filling ratio of the C-shaped PHP should be selected based on the actual operating power to achieve the best heat transfer effect. In the pre-startup stage of the PHP, the thermal resistance during the power-up process was slightly lower than that during the power-down process. After startup, the thermal resistance during the power-up process became slightly higher than that during the power-down process. This difference was suppressed when the filling ratio increased from 50% to 60%.

Key words: pulsating heat pipe, heat transfer, flow, experimental validation, heat transfer analysis