National Engineering Laboratory for Pipeline Safety, MOE Key Laboratory of Petroleum Engineering, Beijing Key Laboratory of Urban Oil and Gas Distribution Technology , China University of Petroleum , Beijing 102249 , China.
School of Mechanical Engineering, Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development , Beijing Institute of Petrochemical Technology , Beijing 102617 , China.
Langmuir. 2018 Nov 27;34(47):14234-14248. doi: 10.1021/acs.langmuir.8b03044. Epub 2018 Nov 14.
In this paper, the molecular dynamics simulation method is utilized to investigate the phase transition behavior of an argon film placed on cavity substrates with different wettability conditions. A simple Lennard-Jones liquid is heated by a metal platinum substrate at different temperatures, and a complete process of bubble nucleation is successfully visualized on the cavity substrate at temperatures of 150 and 160 K. Moreover, the bubble nucleation behavior shows dependence on cavity wettability. A layer of liquid atom is attracted to the strongly hydrophilic cavity and obtains more energy to nucleate first. In contrast, the liquid atom suffers a large repulsive force from the metal atom in the hydrophobic cavity, thus an original small bubble nucleus stably stays inside before the incipient boiling time. With an increase in the heating time, the original bubble nucleus grows up from the hydrophobic cavity. This bubble nucleation behavior on a hydrophobic cavity is in agreement with macro theory, which states that a cavity provides an original nucleus for bubble formation and growth. Besides, cavity wettability plays a crucial role in the incipient boiling temperature of an argon film. The incipient boiling temperature increases with the weakening of the cavity hydrophobicity, and this trend is in accordance with macro experiments, which show that liquid is easier to boil on a more hydrophobic substrate.
本文利用分子动力学模拟方法研究了不同润湿性条件下腔基底上氩膜的相转变行为。通过对金属铂基底进行不同温度的加热,成功地在腔基底上可视化了温度为 150 和 160 K 时的气泡成核完整过程。此外,气泡成核行为表现出对腔润湿性质的依赖性。一层液原子被强烈亲水的腔所吸引,并获得更多的能量以首先成核。相比之下,在疏水性腔中,液原子受到来自金属原子的很大的斥力,因此在初始沸腾时间之前,原始的小气泡核稳定地存在于内部。随着加热时间的增加,原始气泡核从疏水性腔中长大。这种在疏水性腔上的气泡成核行为与宏观理论一致,即腔为气泡的形成和生长提供了原始核。此外,腔润湿性在氩膜的初始沸腾温度中起着至关重要的作用。初始沸腾温度随腔疏水性的减弱而升高,这一趋势与宏观实验一致,表明液体在更疏水的基底上更容易沸腾。