Heat transfer characteristics of super-hydrophilic and super-hydrophobic matched ultra-thin heat pipe

doi:10.16085/j.issn.1000-6613.2017-1667

Abstract

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

摘要： 超薄热管（UTHP）是解决电子器件在狭小空间内散热问题的理想工具，构造纳米结构是提升超薄热管传热性能的重要方法。本文研制了1.30mm厚的新型超薄热管，用化学的方法对吸液芯和冷凝表面进行改性处理，以实现热管中超亲水与超疏水的匹配，通过实验分析了不同充液比工况下纳米结构以及倾角对热性能的影响。结果表明：纳米结构改变了吸液芯和冷凝表面的浸润性，超亲水吸液芯具有更强的吸水能力，超疏水冷凝表面的滴状冷凝机理促进了冷凝液体回流的效率；在小充液比时，吸液芯中的纳米结构促进了沸腾换热和冷凝液体回流速度，提高了热管的临界热流密度（CHF）；在大充液比时，吸液芯中的纳米结构增大了蒸汽逸出和液体流动阻力，对热性能具有负面作用；超亲水吸液芯和超疏水冷凝表面匹配的样品冷凝热阻偏大，但在任何充液比工况下，均具有最佳的CHF；倾角对热性能影响较大，当蒸发段位于冷凝段正下方时热性能最佳。

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

CLC Number:

LIU Changquan, XU Jinliang, JI Xianbing. Heat transfer characteristics of super-hydrophilic and super-hydrophobic matched ultra-thin heat pipe[J]. Chemical Industry and Engineering Progress, 2018, 37(06): 2067-2076.

刘昌泉, 徐进良, 纪献兵. 超亲水/超疏水匹配超薄热管的传热特性[J]. 化工进展, 2018, 37(06): 2067-2076.

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