Heat transfer characteristics of ultra-thin flat heat pipe with nano-modified porous wick

doi:10.11949/j.issn.0438-1157.20170638

Abstract

Abstract:

A new type ultra-thin flat heat pipe (UTFHP) with a total thickness of 1.30 mm was prepared by using multiscale composite structures composed of porous layer (PL) and porous wire (PW) as wicks. After chemical modification treatment, the nanostructures modified the surface of the wick, which had super-hydrophilic properties. The thermal performance of UTFHP was investigated with deionized water used as the working fluid. The effects of the nanostructures, filling ratios and inclination angles on thermal properties of UTFHP were analyzed at different heating powers. The results show that the nanostructures can greatly increase the critical heat flux (CHF) and reduce the total thermal resistance of UTFHP when the filling ratio is 25%. Compared with the sample without nano, the CHF is increased by 255% and the minimum total thermal resistance is reduced by 43.2% at the horizontal angle. In addition, when the filling ratio is low, the nanostructures can reduce the thermal resistance of condensation in the entire heating power range but increase the thermal resistance of the evaporator because of greater flow resistance at low heating power. But the nanostructures inhibit the heat transfer performance of UTFHP when the filling ratio is relatively high. The inclination angles effectively influence the heat transfer characteristics. When the evaporation section is located directly below the condensation section, the thermal performance of UTFHP is optimal. The unmodified and modified heat pipes both have great heat transfer performance, the maximum heating power is 83.7 and 44.3 W respectively.

Key words: ultra-thin flat heat pipe, multiscale, porous media, nanostructure, thermal property, phase equilibria, filling ratio, inclination angle

摘要：

研制了一种总厚度为1.30 mm的新型超薄平板热管（UTFHP），其内部吸液芯是多孔介质底层（PL）和多孔介质丝（PW）组成的多尺度复合结构。经过化学改性处理，吸液芯表面生成纳米结构，具有超亲水特性。对热管的热性能进行实验研究，分析纳米结构、充液比以及角度对热性能的影响。结果表明，充液比为25%时，与未改性的热管相比，改性热管的临界热通量（CHF）提高了255%、总热阻最大可降低43.2%；纳米结构降低了冷凝段热阻，但在小功率时增大了蒸发段热阻。在高充液比时，纳米结构抑制热管的传热性能。角度对热管的热性能影响较大，当蒸发段位于冷凝段的正下方时，热管的热性能最佳。未改性和改性的热管都具有良好的传热特性，最高功率分别为83.7和44.3 W。

关键词: 超薄平板热管, 多尺度, 多孔介质, 纳米结构, 热性能, 相平衡, 充液比, 倾角

CLC Number:

LIU Changquan, SHANG Wei, ZHAO Jugui, JI Xianbing, WU Xinming, XU Jinliang. Heat transfer characteristics of ultra-thin flat heat pipe with nano-modified porous wick[J]. CIESC Journal, 2017, 68(12): 4508-4516.

刘昌泉, 尚炜, 赵举贵, 纪献兵, 吴新明, 徐进良. 纳米修饰吸液芯超薄平板热管的传热特性[J]. 化工学报, 2017, 68(12): 4508-4516.

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