An Experimental Investigation on Heat Transfer Performance of a Thermosyphon With External Fins

ABSTRACT This study investigates the thermal performance of a thermosyphon through experiments, focusing on optimizing operational parameters and understanding transient behavior. A two‐phase thermosyphon finds wide applications across various engineering domains, with its internal vapor–liquid phase change and flow dynamics being crucial factors influencing heat transfer efficiency. A thorough analysis of the heat transfer mechanism in thermosyphons (2 m in length) designed for cooling nuclear fuel storage, particularly under different operating conditions, is essential for optimizing their thermal design and performance. In this study, heat loads (300–600 W), filling‐ratio (40%–100%), operating pressure, and inclination angle (60°−90°) of the thermosyphon are varied to analyze its performance of heat transfer in terms of transient temperature variation and thermal resistance. The results indicate that among the tested filling‐ratios, a 60% filling‐ratio is optimal for efficient thermosyphon operation. Furthermore, the thermal resistance decreased with higher heat loads applied to the evaporator, demonstrating an enhanced heat transfer. The presence of non‐condensable gases (NCGs) is found to increase the evaporator‐to‐condenser temperature difference, impeding performance; however, their removal improves startup behavior and overall heat transfer efficiency. This parametric and methodological analysis provides comprehensive insights into the role of operational conditions in thermosyphon performance. The findings can be applied to optimize passive cooling systems in electronics, energy storage, and nuclear safety applications.