A novel self-venting annular wick for heat pipes: Experimental and comparative performance analysis with several wick structures

Abstract

This study provides a comprehensive experimental and comparative evaluation of water heat pipe performance across seven distinct wick structures, with particular emphasis on a newly developed self-venting annular wick design. The investigation addresses a key challenge in high-performance heat pipes, capillary limit and dry-out, by applying the meniscus coalescence technique to enhance vapor and gas removal. Porosity, permeability, and effective pore radius were characterized using the rate-of-rise method in both with-tube and without-tube configurations. Thermal experiments were conducted in a modular water heat pipe test facility to make a direct performance comparison across all wick types under controlled boundary conditions. Results reveal that self-venting annular and composite annular wicks significantly outperform conventional screen, crescent, and artery configurations in maximum heat transport capacity. The self-venting annular wick demonstrated the highest capillary limit, achieving a 29.2 % enhancement over the conventional annular design, primarily due to its ability to prevent vapor blockages and sustain continuous liquid delivery to the evaporator. These findings show the critical role of wick geometry and venting design in overcoming capillary limitations, and provide practical design guidelines for next-generation, high-capacity heat pipe systems.