In heat transfer systems, how water condenses on the surface is critical to the energy efficiency of the system. With fixed surface wettability, hydrophilic surfaces enhance the nucleation rate but result in filmwise condensation due to pinning effect, which impedes the heat transfer between water vapor and surface during droplet growth. A hydrophilic surface with high drop mobility is realized with static tailored wettability surfaces, while tunable surfaces have potential in more comprehensive manipulation in condensation with different scale in time and scale. However, the mechanism has rarely been investigated and elucidated. In this paper, we investigate water condensation on a tunable surface originated from surface tension distribution control. The surface tension distribution under applied electric field is modeled and tested. We demonstrate that the surface tension manipulated by liquid crystal orientation alters the nucleation site density. Also, the periodic surface tension distribution aligns condensed water drops and decelerates the radius growth of droplets. The mechanism of active water condensation manipulation can be further applied to other tunable surfaces for various applications such as atmospheric water generator, heat transfer systems, and desalination systems.

中文翻译：

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源自分子取向的可切换表面上的水凝结动力学

在传热系统中，水如何在表面冷凝对系统的能源效率至关重要。由于固定的表面润湿性，亲水性表面提高了成核率，但由于钉扎效应导致膜状冷凝，这阻碍了液滴生长过程中水蒸气和表面之间的热传递。具有高液滴迁移率的亲水表面通过静态定制的润湿性表面实现，而可调表面在不同时间和尺度的冷凝过程中具有更全面的控制潜力。然而，其机制很少被研究和阐明。在本文中，我们研究了源自表面张力分布控制的可调表面上的水冷凝。对施加电场下的表面张力分布进行建模和测试。我们证明了由液晶取向控制的表面张力会改变成核位点密度。此外，周期性的表面张力分布使凝结的水滴对齐并减慢了水滴半径的增长。主动水冷凝操纵的机制可以进一步应用于其他可调表面，用于各种应用，例如大气水发生器、传热系统和海水淡化系统。