Qiang Weili, Lan Zhong, Du Bingang, Ren Wenzhi, Xu Wei, Wen Rongfu, Ma Xuehu
State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory of Clean Utilization of Chemical Resources, Institute of Chemical Engineering, Dalian University of Technology, Dalian 116024, PR China.
Langmuir. 2022 Aug 23;38(33):10192-10201. doi: 10.1021/acs.langmuir.2c01264. Epub 2022 Aug 12.
For vapor condensation, the control of heterogeneous nucleation and spatial distribution of nuclei are crucial for regulating droplet dynamics and improving condensation efficiency. However, due to the complex characteristics of multicomponent, multiphase, and multiscale, the underlying mechanism of mixed vapor condensation remains unclear, especially at the nucleation stage. In this paper, we focus on the enrichment effects of non-uniform wettability surfaces by molecular dynamics simulation, which could intensify the droplet nucleation and growth processes in a water-air mixed system. The results clarify the inhibitory effect of non-condensable gas on droplet nucleation and prove that only 1% of non-condensable gas could reduce one half of the condensation performance from a molecular perspective. Furthermore, non-uniform surfaces are designed to promote the efficient enrichment of vapor molecules on nucleation sites, and the synergistic effect of hydrophilic and hydrophobic regions is proposed. In addition, the non-uniform wettability surfaces are characterized by varying the proportion and dispersion of hydrophilic regions. The results reveal that an optimal proportion of hydrophilic region ( = 5/6) could furnish the non-uniform surface with the best transfer performance. Moreover, the enhancement of condensation performance can also be achieved through the dispersed arrangement of hydrophilic regions. The results provide guidance for the optimized design of functionalized surfaces with enhanced mixed vapor condensation.
对于蒸汽冷凝，控制异质成核和核的空间分布对于调节液滴动力学和提高冷凝效率至关重要。然而，由于多组分、多相和多尺度的复杂特性，混合蒸汽冷凝的潜在机制仍不清楚，尤其是在成核阶段。在本文中，我们通过分子动力学模拟关注非均匀润湿性表面的富集效应，这可以强化水 - 空气混合系统中的液滴成核和生长过程。结果阐明了不可凝气体对液滴成核的抑制作用，并从分子角度证明仅1%的不可凝气体就能使冷凝性能降低一半。此外，设计非均匀表面以促进蒸汽分子在成核位点上的有效富集，并提出了亲水和疏水区域的协同效应。另外，通过改变亲水区域的比例和分散度来表征非均匀润湿性表面。结果表明，亲水区域的最佳比例（= 5/6）能使非均匀表面具有最佳的传递性能。此外，通过亲水区域的分散排列也可以实现冷凝性能的增强。这些结果为具有增强混合蒸汽冷凝性能的功能化表面的优化设计提供了指导。
