Katre Pallavi, Balusamy Saravanan, Banerjee Sayak, Chandrala Lakshmana Dora, Sahu Kirti Chandra
Department of Chemical Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502 285, Telangana India.
Department of Mechanical and Aerospace Engineering, Indian Institute of Technology Hyderabad, Sangareddy 502 285, Telangana India.
Langmuir. 2021 May 25;37(20):6311-6321. doi: 10.1021/acs.langmuir.1c00806. Epub 2021 May 13.
We investigate the evaporation dynamics of a sessile droplet of ethanol-water binary mixtures of different compositions laden with alumina nanoparticles and compare with the no-loading condition at different substrate temperatures. Shadowgraphy and infrared imaging methods are used, and the experimental images are postprocessed using a machine learning technique. We found that the loading and no-loading cases display distinct wetting and contact angle dynamics. Although the wetting diameter of a droplet decreases monotonically in the absence of loading, the droplet with 0.6 wt % nanoparticle loading remains pinned for the majority of its lifetime. The temporal variation of the normalized droplet volume in the no-loading case has two distinct slopes, with ethanol and water phases dominating the early and late stages of evaporation, respectively. The normalized droplet volume with 0.6 wt % loading displays a nearly linear behavior because of the increase in the heat transfer rate. Our results from infrared imaging reveal that a nanofluid droplet displays far richer thermal patterns than a droplet without nanoparticle loading. In nanoparticle-laden droplets, the pinning effect, as well as the resulting thermo-capillary and thermo-solutal convection, causes more intense internal mixing and a faster evaporation rate. Finally, a theoretical model is also developed that satisfactorily predicts the evaporation dynamics of binary nanofluid droplets.
我们研究了负载氧化铝纳米颗粒的不同成分乙醇 - 水二元混合物的 sessile 液滴的蒸发动力学，并与不同基板温度下的无负载条件进行比较。使用了阴影成像和红外成像方法，并且使用机器学习技术对实验图像进行后处理。我们发现，负载和无负载情况表现出不同的润湿和接触角动力学。在无负载情况下，液滴的润湿直径单调减小，而负载 0.6 wt% 纳米颗粒的液滴在其大部分寿命期间保持固定。无负载情况下归一化液滴体积的时间变化有两个不同的斜率，乙醇和水相分别主导蒸发的早期和后期阶段。由于传热速率的增加，负载 0.6 wt% 的归一化液滴体积显示出近乎线性的行为。我们的红外成像结果表明，纳米流体液滴比无纳米颗粒负载的液滴表现出丰富得多的热模式。在负载纳米颗粒的液滴中，钉扎效应以及由此产生的热毛细和热溶质对流导致更强烈的内部混合和更快的蒸发速率。最后，还开发了一个理论模型，该模型令人满意地预测了二元纳米流体液滴的蒸发动力学。
