氢氧化铜纳米针阵列滴状冷凝传热研究

发布时间：2018-03-22 12:22

本文选题：强化滴状冷凝传热　切入点：氢氧化铜纳米针阵列　出处：《河北工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：冷凝是自然界中常见的一种相变现象,在包括发电、热处理、海水淡化、环境保护等工业上有广泛的应用。在过去的80年,研究者一直致力于在金属表面构筑稳定的滴状冷凝界面,使冷凝液滴长到毛细尺寸后在重力作用下能够离开界面,从而有效地提高界面的传热性能。最近的研究表明:通过构筑合适的超疏水界面可以有效地加快液滴的移动速率,甚至能使冷凝微液滴依靠融合释放的能量就能自驱动弹离界面,并且理论研究也证实该界面能够极大地提升冷凝传热性能。在本论文中我们通过在铜基表面构筑氢氧化铜纳米针阵列并经过低表面能化学修饰后,得到具有冷凝微液滴自驱离性能的纳米界面,并且在蒸汽工况下证实该表面具有强化冷凝传热的性能。具体研究内容及结果如下:使用电沉积法在铜试样上构筑纳米针阵列状的结构,通过调控反应条件以及表面疏水化处理,得到具有超疏水性能的界面。并在大气环境下对其表面微液滴的自驱离行为进行表征。其次,我们对氢氧化铜纳米针阵列表面进行低温传热性能研究,结果表明:纳米针阵列结构的热通量平均为同样处理的光滑界面的3倍左右,而传热系数则高达5倍左右。此外,在低温蒸汽的工况下,使用高倍高分辨率的CCD观察液滴在氢氧化铜纳米针阵列结构界面的动态行为;并系统研究了随着过冷度的增加液滴行为的变化,发现液滴在界面上的自驱动(弹离)模式需要在较低的饱和度(S1.12)以及较低的过冷度(△T2K)下才能发生。最后,我们系统研究了在不同过冷度下氢氧化铜纳米针阵列结构界面的冷凝传热,发现随着过冷度的提高,传热系数表现出先上升后下降的特点,并且结合高速高分辨CCD捕捉的冷凝现象发现:在自驱动模式下,样品表面的传热系数最高,传热效果最好。综上,本论文的研究表明了氢氧化铜纳米针阵列界面具有微尺度冷凝液滴自驱离性能,并且在蒸汽工况下具有优秀的冷凝传热性能。上述研究不仅为开发新型冷凝强化传热提供了新方向,也为金属材料冷凝传热性能的开发提供新的思路。
[Abstract]:Condensation, a common phase change phenomenon in nature, has been widely used in industries such as power generation, heat treatment, seawater desalination, environmental protection, and so on. Researchers have been working to build stable dripping condensate interfaces on metal surfaces that allow droplets to grow to the size of their capillaries and get out of the interface by gravity. Recent studies have shown that by constructing suitable superhydrophobic interfaces, the droplet moving rate can be effectively accelerated. Even the condensing microdroplets can self-drive the interface, depending on the energy released from the fusion. The theoretical study also proves that the interface can greatly improve the heat transfer performance of condensation. In this thesis, we have constructed copper hydroxide nanoscale arrays on the surface of copper and chemically modified with low surface energy. Nanocrystalline interface with condensing microdroplet self-displacing property was obtained. It is proved that the surface has the property of enhancing condensation heat transfer under the condition of steam. The specific research contents and results are as follows: the nano-needle array structure is constructed on copper sample by electrodeposition method. The superhydrophobic interface was obtained by controlling the reaction conditions and surface hydrophobic treatment. The self-expulsion behavior of micro-droplets on the surface was characterized under atmospheric conditions. The low temperature heat transfer properties of copper hydroxide nanoscale arrays are studied. The results show that the average heat flux of the nanocrystalline needle arrays is about 3 times of that of the smooth interface treated by the same treatment, while the heat transfer coefficient is about 5 times. Under the condition of low temperature steam, the dynamic behavior of droplets at the interface of copper hydroxide nanoscale array was observed by high power and high resolution CCD, and the change of droplet behavior with the increase of undercooling was systematically studied. It is found that the self-driving (ejection) mode of droplets at the interface requires a lower saturation (S1.12) and a lower undercooling (T2K). Finally, The condensation heat transfer at the interface of copper hydroxide nanoscale needle arrays with different undercooling is studied systematically. It is found that with the increase of supercooling, the heat transfer coefficient increases first and then decreases. Combined with the condensation phenomenon captured by high speed and high resolution CCD, it is found that the surface heat transfer coefficient of the sample is the highest and the heat transfer effect is the best in the self-driving mode. The results show that the interface of copper hydroxide nanocrystalline needle array has micro-scale condensing droplet self-driving property. This study not only provides a new direction for the development of new condensing enhanced heat transfer, but also provides a new way of thinking for the development of condensation heat transfer performance of metal materials.
【学位授予单位】：河北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG178;TB301

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