Study on Flow Characteristics of Flexible Pulsating Heat Pipe

This study aims to determine the optimal design conditions for flexible pulsating heat pipe (PHP) utilizing fluororubber tubes by investigating key variables such as filling ratio and turn number. Experimental results indicate that methanol is preferable over distilled water as the working fluid due to its lower boiling point and superior thermal properties. Among tested conditions, a methanol filling ratio of 20% and four turns demonstrates the most active oscillation with a short recovery time, suggesting effective heat transfer through evaporation and condensation processes. In contrast, a 10% filling ratio with four turns exhibits relatively stable heat transfer, as indicated by a longer oscillation duration, but experiences slower heat transfer due to extended recovery times. These findings highlight the critical role of filling ratio and turn number in heat pipe design. Additionally, the experiment reveals challenges in maintaining the vacuum state of fluororubber tubes over time, leading to performance degradation. Since the vacuum state is essential for optimal heat transfer, future research should focus on improving vacuum maintenance and sealing technologies.