关键词: 超薄热管, 纳米结构, 超亲水, 超疏水, 多孔介质, 传热, 充液比, 倾角

Abstract: Ultra-thin heat pipe(UTHP) is an ideal tool to solve the problem of heat dissipation in the small space of electronic devices, and the construction of nanostructure is an important method to improve the heat transfer performance of UTHP. In this paper, we developed a new type of UTHP with 1.30mm thickness and used chemical method to modify the porous wicks and the condensation surface to match the super-hydrophilic and super-hydrophobic. The effects of nanostructures and inclination angles at different filling ratios on thermal performance were analyzed by experiments. Results showed that the nanostructures change the wettability of the porous wicks and the condensation surface. The super-hydrophilic porous wicks have stronger water absorbing ability, and the droplet condensation mechanism of the super-hydrophobic condensation surface promotes the condensate reflux efficiency. In the small filling ratio, the nanostructure in the porous wicks facilitates the boiling heat transfer and condensation liquid reflux velocity, and then increases the resistance of vapor escaping and the liquid flow in the large filling ratio, which has a negative effect on the thermal performance. The sample with super-hydrophilic porous wicks and super-hydrophobic condensation surface has a large condensation heat resistance, but it has best critical heat fluxes(CHF) at any filling ratios. The inclination angle has a great influence on the thermal performance, and the UTHP has optimal heat performance when the evaporation section is directly below the condensation section.

Key words: ultra-thin heat pipe, nanostructure, super-hydrophilic, super-hydrophobic, porous media, heat transfer, filling ratio, inclination angle