Zhang Jia-Jian, Huang Haibo, Lu Xi-Yun
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Langmuir. 2020 Apr 7;36(13):3439-3451. doi: 10.1021/acs.langmuir.0c00019. Epub 2020 Mar 25.
The evaporation mechanism of miscible binary nanodroplets from heated homogeneous surfaces was studied by molecular dynamics simulations, which has never been studied before. The binary droplets contain a hydrophilic component (type-2 particles) and a hydrophobic component (type-3 particles). It is shown that liquid-liquid interaction strength (ε) and hydrophilic particle number fraction (φ) have great influence on the surface tension, wetting characteristics, evaporation patterns, evaporation rate, and local mass flux. It is observed that when ε ≥ 1, or φ ≈ 0.5, the evaporation mode is the constant-contact-angle mode. Otherwise, it is the mixed mode. We found that the evaporation rate becomes faster when φ and ε increase. The droplets become more hydrophilic when φ increases, which promotes heat transfer efficiency between the liquid-solid interface. Besides, a larger ε promotes the heat transfer inside the droplet. The mass transfer to the vapor phase occurs preferentially in the vicinity of TPCL (three phase contact line) in the hydrophilic systems (θ < θ), where θ is the critical contact angle, while in most hydrophobic systems (θ > θ), the mass flux close to the TPCL is suppressed. We found that θ ∈ (102°-106°), which is different from the theoretical one, θ = 90°. The discrepancy is attributed to the existence of the adsorption layer near the TPCL.
通过分子动力学模拟研究了可混溶二元纳米液滴在加热均匀表面上的蒸发机制，此前从未有人对此进行过研究。二元液滴包含亲水性成分（2型颗粒）和疏水性成分（3型颗粒）。结果表明，液 - 液相互作用强度（ε）和亲水性颗粒数分数（φ）对表面张力、润湿特性、蒸发模式、蒸发速率和局部质量通量有很大影响。观察到当ε≥1或φ≈0.5时，蒸发模式为恒定接触角模式。否则，为混合模式。我们发现当φ和ε增加时，蒸发速率会变快。当φ增加时，液滴变得更亲水，这促进了液 - 固界面之间的传热效率。此外，更大的ε促进了液滴内部的传热。在亲水性系统（θ < θ，其中θ为临界接触角）中，向气相的传质优先发生在三相接触线（TPCL）附近，而在大多数疏水性系统（θ > θ）中，靠近TPCL的质量通量受到抑制。我们发现θ∈（102° - 106°），这与理论值θ = 90°不同。这种差异归因于TPCL附近吸附层的存在。
