Kadhim Mustafa A, Kapur Nikil, Summers Jonathan L, Thompson Harvey
School of Mechanical Engineering , University of Leeds , Leeds , United Kingdom.
Mechanical Engineering Department , University of Babylon , Babylon , Iraq.
Langmuir. 2019 May 14;35(19):6256-6266. doi: 10.1021/acs.langmuir.8b03601. Epub 2019 May 3.
The evaporation characteristics of sessile droplets on heated hydrophobic and hydrophilic surfaces are investigated. Results are reported for the evaporation of water droplet volumes covering a range of shapes dominated by surface tension or gravity and over a range of temperatures between 40 and 60 °C. The weight evolution and total time of evaporation is measured using a novel self-contained heating stage on a high resolution analytical balance, which has advantages over visualization measurement techniques as it allows free choice of the initial droplet size and surface and the ability to record the droplet evaporation right through to the final stages of droplet life. Evaporation is modeled through a combination of a constant contact area and a constant contact angle model with the switch from the former to the latter occurring when the contact angle falls below its predetermined receding value. Theoretical results compare well with the experimental results for the hydrophobic substrate. However, a significant deviation is observed for the hydrophilic substrate due to the combined effects of the droplet surface cooling due to evaporation and buoyancy effects that are not included in the model. The proposed method of using the stick-slip model offers a convenient means of modeling droplet evaporation by mimicking the drying modes based on initial measurements of the static and receding contact angles.
研究了加热的疏水和亲水表面上静态液滴的蒸发特性。报告了覆盖一系列由表面张力或重力主导的形状的水滴体积在40至60°C范围内的蒸发结果。使用高分辨率分析天平上的新型独立加热台测量重量变化和蒸发总时间，该加热台比可视化测量技术具有优势，因为它允许自由选择初始液滴尺寸和表面，并能够记录液滴蒸发直至液滴寿命的最后阶段。通过恒定接触面积模型和恒定接触角模型的组合对蒸发进行建模，当接触角低于其预定的后退值时，从前者切换到后者。对于疏水基底，理论结果与实验结果比较吻合。然而，由于模型中未包括的蒸发引起的液滴表面冷却和浮力效应的综合作用，在亲水基底上观察到显著偏差。所提出的使用粘滑模型的方法通过基于静态和后退接触角的初始测量模拟干燥模式，提供了一种方便的液滴蒸发建模方法。
