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Droplet Evaporation Dynamics of Low Surface Tension Fluids Using the Steady Method
Langmuir ( IF 3.9 ) Pub Date : 2020-11-09 , DOI: 10.1021/acs.langmuir.0c02272
A. Alperen Günay 1 , Marisa Gnadt 1 , Soumyadip Sett 1 , Hamed Vahabi 2 , Arun K. Kota 3 , Nenad Miljkovic 1, 4, 5, 6
Affiliation  

Droplet evaporation governs many heat- and mass-transfer processes germane in nature and industry. In the past 3 centuries, transient techniques have been developed to characterize the evaporation of sessile droplets. These methods have difficulty in reconciling transient effects induced by the droplet shape and size changes during evaporation. Furthermore, investigation of evaporation of microdroplets residing on wetting substrates, or fluids having low surface tensions (<30 mN/m), is difficult to perform using established approaches. Here, we use the steady method to study the microdroplet evaporation dynamics of low surface tension liquids. We start by employing the steady method to benchmark with water droplets having base radii (20 ≤ Rb ≤ 260 μm), apparent advancing contact angle (45° ≤ θa,app ≤ 162°), surface temperature (30 < Ts < 60 °C), and relative humidity (40% < ϕ < 60%). Following validation, evaporation of ethanol (≈22 mN/m), hexane (≈18 mN/m), and dodecane (≈25 mN/m) were studied for 90 ≤ Rb ≤ 400 μm and 10 < Ts < 25 °C. We elucidate the mechanisms governing the observed behavior using heat and mass transport scaling analysis during evaporation, demonstrating our steady technique to be particularly advantageous for microdroplets, where Marangoni and buoyant forces are negligible. Our work not only elucidates the droplet evaporation mechanisms of low surface tension liquids but also demonstrates the steady method as a means to study phase change processes.

中文翻译:

采用稳态法的低表面张力流体的液滴蒸发动力学

液滴蒸发支配着自然界和工业界许多紧密联系的传热和传质过程。在过去的三个世纪中,已经开发出瞬态技术来表征无柄液滴的蒸发。这些方法难以协调蒸发过程中液滴形状和尺寸变化引起的瞬态效应。此外,使用已建立的方法难以进行对位于湿润衬底上的微滴或具有低表面张力(<30 mN / m)的流体的蒸发的研究。在这里,我们使用稳定的方法来研究低表面张力液体的微滴蒸发动力学。我们首先通过采用稳定方法与具有碱半径(20≤水滴基准- [R b ≤260微米),表观前进接触角(45°≤θa, app≤162°),表面温度(30 < T s <60°C)和相对湿度(40%<ϕ <60%)。下面的验证,蒸发乙醇(≈22mN / m的),己烷(≈18mN / m的),和十二烷(≈25mN / m的)进行了研究90≤ [R b ≤400微米和10 < Ť小号<25° C。我们使用蒸发过程中的热量和质量传递比例分析来阐明控制观察到的行为的机制,这表明我们的稳定技术对于微滴特别有利,因为在微滴中,Marangoni和浮力可忽略不计。我们的工作不仅阐明了低表面张力液体的液滴蒸发机理,而且还证明了稳定的方法是研究相变过程的一种手段。
更新日期:2020-11-25
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