Chang Chia-Ming, Lin Yi-Hsin, Reshetnyak Victor
Department of Photonics, College of Electrical and Computer Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.
Theoretical Physics Department, Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine.
Phys Rev E. 2021 Sep;104(3-1):034701. doi: 10.1103/PhysRevE.104.034701.
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.
在传热系统中，水在表面的凝结方式对于系统的能源效率至关重要。在表面润湿性固定的情况下，亲水表面会提高成核速率，但由于钉扎效应会导致膜状凝结，这在液滴生长过程中阻碍了水蒸气与表面之间的热传递。通过静态定制润湿性表面可实现具有高液滴迁移率的亲水表面，而可调表面在对不同时间尺度和空间尺度的凝结进行更全面的操控方面具有潜力。然而，其机制很少得到研究和阐明。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凝结现象。对施加电场下的表面张力分布进行了建模和测试。我们证明，由液晶取向操控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会使凝结的水滴排列整齐，并减缓液滴半径的增长。主动水凝结操控机制可进一步应用于其他可调表面，以用于各种应用，如大气水发生器、传热系统和海水淡化系统。
