Investigation of sessile droplet evaporation using a transient two-step moving mesh model
Investigation of sessile droplet evaporation using a transient two-step moving mesh model
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DOI：
10.1016/j.ijheatmasstransfer.2023.124151
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发表时间：
2023
影响因子：
5.2
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中科院分区：
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液滴在表面上的蒸发是自然界和工业应用中必不可少的普遍现象，从电子器件的热管理到基于自组装的制造。在这项研究中，水滴在薄石英基板上的蒸发进行了分析，使用非定常两步任意拉格朗日-欧拉（ALE）移动网格模型，其中蒸发过程中模拟恒定接触半径（CCR）和接触角（CCA）模式。数值模型考虑了气体域中的质量传递、液体和气体域中的流动以及固体、液体和气体域中的热传递。此外，该模型还考虑了界面力平衡，包括热毛细应力，以获得瞬时液滴形状。涉及未加热的石英基板上的液滴蒸发的实验同意模型预测的接触半径，接触角，和液滴体积。模型结果表明，温度和速度分布在蒸发水滴表明，最低温度是在液-气界面，和一个单一的漩涡存在的液滴的寿命的主要持续时间。由于蒸发冷却，未加热的基板的温度也显著降低。界面蒸发通量的分布，这取决于整个液滴和周围介质中的对流传热，显示出三相接触线附近的最高值。此外，该模型还预测蒸发动力学时，基板被加热，并暴露于不同的平流条件。通常，较高的蒸发速率由较高的衬底加热和平流速率产生。然而，基板加热和平流在周围气体的CCR和CCA模式的相对持续时间的影响最小，对于一个给定的后退接触角。具体来说，在这种情况下，衬底加热速率增加40倍或气体速度增加7.5倍只能使这些相对持续时间改变3%。这项研究还强调了表面润湿性的重要性，这会影响蒸发动力学的数值模型探索的所有条件。
The evaporation of droplets on surfaces is a ubiquitous phenomenon essential in nature and industrial applications ranging from thermal management of electronics to self-assembly-based fabrication. In this study, water droplet evaporation on a thin quartz substrate is analyzed using an unsteady two-step arbitrary Lagrangian-Eulerian (ALE) moving mesh model, wherein the evaporation process is simulated during the constant contact radius (CCR) and contact angle (CCA) modes. The numerical model considers mass transfer in the gas domain, flow in the liquid and gas domains, and heat transfer in the solid, liquid, and gas domains. Besides, the model also accounts for interfacial force balance, including thermocapillary stresses, to obtain the instantaneous droplet shape. Experiments involving droplet evaporation on unheated quartz substrates agree with model predictions of contact radius, contact angle, and droplet volume. Model results indicating temperature and velocity distribution across an evaporating water droplet show that the lowest temperatures are at the liquid-gas interface, and a single vortex exists for the predominant duration of the droplet's lifetime. The temperature of the unheated substrate is also significantly reduced due to evaporative cooling. The interfacial evaporation flux distribution, which depends on heat transfer across the droplet and advection in the surrounding medium, shows the highest values near the three-phase contact line. In addition, the model also predicts evaporation dynamics when the substrate is heated and exposed to different advection conditions. Generally, higher evaporation rates result from higher substrate heating and advection rates. However, substrate heating and advection in the surrounding gas have minimal effects on the relative durations of CCR and CCA modes for a given receding contact angle. Specifically, in this case, a 40× increase in substrate heating rate or 7.5× increase in gas velocity can only change these relative durations by 3%. This study also highlights the importance of surface wettability, which affects evaporation dynamics for all the conditions explored by the numerical model.