Dependences of formation and transition of surface condensation mode on wettability and temperature difference.
Dependences of formation and transition of surface condensation mode on wettability and temperature difference.
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DOI：
10.1021/acs.langmuir.9b03339
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
J. Pu;Jie Sun;Q. Sheng;Wen Wang;Hua Sheng Wang
中科院分区：
文献类型：
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作者：
J. Pu;Jie Sun;Q. Sheng;Wen Wang;Hua Sheng Wang
本文采用分子动力学模拟方法研究了表面凝结模式的形成和转变与润湿性（β）和温差（ΔT）的关系。在大量分子动力学模拟结果的基础上，建立了不同表面凝结模式与β和ΔT的关系图，揭示了5种表面凝结形成机制和2种表面凝结转变机制。在低β和ΔT下，高能量势垒（ΔG*）阻止任何团簇存活，因此没有观察到凝聚（NC）。滴状冷凝（DWC）的形成可以从成核或膜破裂演变。同样，膜状冷凝（FWC）的形成可以由成核或吸附诱导膜形成。根据经典成核理论，由ΔG* 决定NC和DWC之间的转变。DWC和FWC之间的过渡取决于凝结液膜的稳定性，在该稳定性范围内，存在着低β驱动的液滴收缩和破裂趋势与高ΔT驱动的液滴保持生长趋势之间的竞争。最后，我们提出了一个示意性的概述所有的机制，揭示了更好地理解的物理现象的表面冷凝。
In this work, we use molecular dynamics (MD) simulations to investigate the dependences of formation and transition of surface condensation mode on wettability (β) and temperature difference (ΔT). We build a map of different surface condensation modes against β and ΔT based on plenty of MD simulation results, through which we reveal five formation mechanisms and two transition mechanisms. At low β and ΔT, the high energy barrier (ΔG*) prevents any clusters to survive, therefore no condensation (NC) is observed. The formation of dropwise condensation (DWC) could evolve either from nucleation or from film-rupture. Similarly, the formation of filmwise condensation (FWC) could form either from nucleation or adsorption-induced film. The transition between NC and DWC is determined by ΔG* based on classical nucleation theory. The transition between DWC and FWC depends on the condensate film stability, within which there emerges the competition between the trend of contracting and rupturing to droplet driven by low β and the trend of remaining as growing film driven by high ΔT. We finally present a schematic overview on all the mechanisms revealed for a better understanding of the physical phenomenon of surface condensation.