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首页> 外文期刊>Journal of Heat Transfer >Condensation on Superhydrophobic Copper Oxide Nanostructures
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Condensation on Superhydrophobic Copper Oxide Nanostructures

机译：超疏水氧化铜纳米结构上的缩合

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摘要

Condensation is an important process in both emerging and traditional power generation and water desalination technologies. Superhydrophobic nanostructures promise enhanced condensation heat transfer by reducing the characteristic size of departing droplets via coalescence-induced shedding. In this work, we investigated a scalable synthesis technique to produce functionalized oxide nanostructures on copper surfaces capable of sustaining superhydrophobic condensation and characterized the growth and departure behavior of the condensed droplets. Nanostructured copper oxide (CuO) films were formed via chemical oxidation in an alkaline solution resulting in dense arrays of sharp CuO nanostructures with characteristic heights and widths of ≈1 μm and ≈300 nm, respectively. To make the CuO surfaces superhydrophobic, they were functionalized by direct deposition of a fluorinated silane molecular film or by sputtering a thin gold film before depositing a fluorinated thiol molecular film. Condensation on these surfaces was characterized using optical microscopy and environmental scanning electron microscopy to quantify the distribution of nucleation sites and elucidate the growth behavior of individual droplets with characteristic radii of ≈1-10 μm at supersaturations ≤1.5. Comparison of the measured individual droplet growth behavior to our developed heat transfer model for condensation on superhydrophobic surfaces showed good agreement. Prediction of the overall heat transfer enhancement in comparison to a typical dropwise condensing surface having an identical nucleation density suggests a restricted regime of enhancement limited to droplet shedding radii (≤) 2.5 μm due to the large apparent contact angles of condensed droplets on the fabricated CuO surfaces. The findings demonstrate that superhydrophobic condensation typified by coalescence-induced droplet shedding may not necessarily enhance heat transfer and highlights the need for further quantification of the effects of surface structure on nucleation density and careful surface design to minimize parasitic thermal resistances.
机译：在新兴的和传统的发电以及水脱盐技术中，冷凝都是重要的过程。超疏水纳米结构通过通过聚结诱导的脱落减小了离开的液滴的特征尺寸，从而有望增强冷凝传热。在这项工作中，我们研究了可扩展的合成技术，以在能够维持超疏水性缩合的铜表面上生成功能化的氧化物纳米结构，并表征了缩合液滴的生长和离开行为。纳米结构的氧化铜（CuO）膜是在碱性溶液中通过化学氧化形成的，从而形成了锐利的CuO纳米结构的密集阵列，其特征高度和宽度分别约为≈1μm和≈300nm。为了使CuO表面具有超疏水性，可在沉积氟化硫醇分子膜之前，通过直接沉积氟化硅烷分子膜或通过溅射金薄膜来对CuO表面进行功能化。使用光学显微镜和环境扫描电子显微镜对这些表面上的冷凝进行表征，以量化成核位点的分布，并阐明在饱和度≤1.5时具有约1-10μm特征半径的单个液滴的生长行为。将所测得的单个液滴的生长行为与我们开发的超疏水表面上的冷凝传热模型进行比较，结果显示出良好的一致性。与具有相同成核密度的典型滴状冷凝表面相比，整体传热增强的预测表明，受限的增强机制仅限于液滴脱落半径（≤）2.5μm，这是由于冷凝后的液滴在制造的CuO上的表观接触角大表面。研究结果表明，以聚结引起的液滴脱落为代表的超疏水性缩合反应不一定能增强传热，并强调了需要进一步量化表面结构对成核密度的影响以及精心设计表面以最大程度降低寄生热阻的需求。

著录项

  • 来源
    《Journal of Heat Transfer》 |2013年第9期|091304.1-091304.12|共12页
  • 作者

    Ryan Enright; Nenad Miljkovic; Nicholas Dou; Youngsuk Nam; Evelyn N. Wang;

  • 作者单位

    Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139,Stokes Institute, University of Limerick, Limerick, Ireland;

    Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139;

    Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139;

    Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 Kyung Hee University, Yongin, Korea;

    Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    condensation; superhydrophobic; nanostructure; scalable synthesis; heat transfer; droplet jumping; experimental; modeling;

    机译：缩合;超疏水纳米结构可扩展的综合;传播热量;液滴跳跃实验造型;

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