Experimental investigation on heat transfer performance of ultra-thin flexible polymer heat pipes with hydrophilic nylon mesh wicks

Abstract

With the rapid advancement of flexible electronics, it is crucial to develop efficient and flexible heat dissipation devices to address the issue of excessive localized heat fluxes in confined internal spaces under bending conditions. In this work, the ultra-thin flexible polymer heat pipes (FPHPs) were fabricated using hydrophilic nylon mesh wicks (HNMWs), aluminum-plastic film casings, and composite support structures consisting of coarse nylon mesh and polyimide (PI) vapor channel. The HNMWs with outstanding hydrophilicity and capillary performance exhibit a low water contact angle of 15.9°, a high equilibrated wicking height of 81 mm, and a significantly high capillary coefficient of 9.36 mm/s^0.5. The effects of working fluid filling ratio, mesh number of coarse nylon mesh, and thickness of PI vapor channel, on the heat transfer performance of FPHPs were investigated. Results demonstrate that the optimal filling ratio is 100 %, and that both the mesh number of coarse nylon mesh and thickness of PI vapor channel positively correlate with heat transfer performance of FPHPs. Additionally, the FPHPs achieve outstanding heat transfer performance, with a maximum heat transfer power of up to 11 W, a high equivalent thermal conductivity of up to 9737.58 W/(m·K), and a low thermal resistance of 0.15 K/W. The FPHPs display excellent flexibility with a low thermal resistance of 0.17 K/W, representing only a 13.3 % increase from the value without bending. The proposed FPHPs with excellent heat transfer performance and flexibility hold significant potential for use in high-power flexible electronic devices.