Influence of optimized design of radial layered wick structure on the thermal characteristics of heat pipe

Thermal performance of heat pipes (HPs) is primarily governed by wick structure. However, conventional single sintered copper powder wicks suffer from inherent trade-off between capillary pressure and permeability, limiting their performance under high heat flux conditions. In this study, radial layered sintered copper powder wick with inner fine-particle region and an outer coarse-particle region is proposed to achieve coordinated enhancement of capillary pumping and liquid transport. The radial layered structure enables condensate return through parallel porous pathways, where the inner fine-particle region provides enhanced capillary driving force and the outer coarse-particle region reduces liquid flow resistance. The effects of inner and outer wick particle sizes, gravity orientation, and filling ratio on HP performance are systematically investigated. Results demonstrate that the optimal combination is 100–120 mesh for the inner layer and 80–100 mesh for the outer layer, yielding maximum heat transfer capacity of 90 W and average thermal resistance of 0.022 °C/W. Compared with conventional single wick HPs, the layered structure reduces average thermal resistance by over 50% and increases maximum heat transfer capacity by more than 45.5%. In addition, the capillary limit model is established for the layered HP, with only 4.1% error between theoretical predictions and experimental results. These findings demonstrate that the radial layered wick structure effectively enhances HP thermal performance and provides guidance for high-performance wick design.