Heat transfer performance of an ultra-thin flat heat pipe with a novel gradient-porous wire mesh wick

The miniaturization and increasing power density of electronic devices have created a growing demand for compact and efficient thermal management technologies. Ultra-thin heat pipes have become an important technical approach for thermal management in high-power-density electronic devices because of their high thermal conductivity, compact structure, and excellent temperature uniformity. In this study, a novel ultra-thin flat heat pipe with a gradient-porous planar woven wire mesh wick was proposed. Different mesh numbers were arranged from the evaporator to the condenser to enhance liquid supply in the evaporator and reduce return-flow resistance in the condenser. Visualization experiments were conducted to investigate the flow evolution, thermal resistance, and start-up performance. The results show that the proposed heat pipe maintains stable two-phase circulation at medium and high heating powers and delays evaporator dry-out. A minimum thermal resistance of 0.26 K/W was obtained at a filling ratio of 50%. Even at 20 W, its thermal resistance remained lower than that of the conventional heat pipe at 16 W. Depending on the operating condition, the start-up time was shortened by approximately 4–8 min.