Investigation on heat and mass transfer mechanism within a thermosyphon fin under multiple power distributions

Thermal management in electronics is challenged by increasing power density, where traditional solid fins suffer from poor temperature uniformity due to limited thermal conductivity. This study addresses this by investigating thermosyphon fins, which integrate two-phase phase change to enhance heat transfer. Using combined experimental measurements and numerical simulations, the heat and mass transfer mechanisms have been analyzed under varying heating powers (20–50 W), power distributions, filling ratios (40–70%), and inclination angles (30–75°), compared to solid fins. Key results show that thermosyphon fins reduce thermal resistance by up to 64% and lower hotspot temperature by 6.1 K versus solid fins, particularly when power is concentrated in the lower region. The optimal filling ratio of 50–60% maximizes heat transfer, while inclinations above 60° improve temperature uniformity by over 40% by expanding the two-phase region. In the end, the four distinct regions, evaporation, condensation, dry-out and static areas are distinguished as the fundamental of guide design for enhanced mass transfer. This work provides the first systematic analysis of thermosyphon fins, providing a comprehensive understanding by revealing internal phase-change mechanisms, analyzing influences of various working conditions and offering practical guidelines for high-efficiency cooling applications.