Dynamics of hygroscopic aqueous solution droplets undergoing evaporation or vapour absorption
| Autor: | Adam Williams, Zhenying Wang, Khellil Sefiane, George Karapetsas, Yasuyuki Takata, Prashant Valluri |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Mass flux
Aqueous solution Marangoni effect Materials science Capillary action Mechanical Engineering Evaporation technology industry and agriculture 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Lubrication theory Physics::Fluid Dynamics Mechanics of Materials Chemical physics 0103 physical sciences Absorption (chemistry) 010306 general physics 0210 nano-technology Water vapor |
| Zdroj: | Wang, Z, Karapetsas, G, Valluri, P, Sefiane, K, Williams, A & Takata, Y 2021, ' Dynamics of hygroscopic aqueous solution droplets undergoing evaporation or vapour absorption ', Journal of Fluid Mechanics, vol. 912, no. A2, pp. 1-30 . https://doi.org/10.1017/jfm.2020.1073 Journal of Fluid Mechanics |
| DOI: | 10.1017/jfm.2020.1073 |
| Popis: | Studies on the evaporation of multicomponent droplets have revealed complex and important physical mechanisms, induced by preferential phase change or mediated by external vapour sources, e.g. occurrence of density-driven flows, phase separation, transient Marangoni flow and solutal effects, etc. With the addition of hygroscopic salts, the adhesive property of the droplet can be tuned, and the direction of water vapour mass flux reversed. This paper focuses on the dynamics of hygroscopic aqueous solution droplets, and analyses the interplay between different physical processes. Specifically, a lubrication-type model is established with the assumption of a precursor film in front of the three-phase contact line, which indicates qualitative agreement with our experimental results, quantitatively with respect to the initial spreading rates and qualitatively with respect to the overall behaviour. We derive the expression of absorptive mass flux combining the balance of chemical potential across the solution–air interface and the Hertz–Knudsen equation. Depending on the droplet state and the ambient condition, evaporation or vapour absorption occurs. The evaporative/absorptive mass flux varies both spatially and temporally as the droplet approaches equilibrium. It is demonstrated that the dominating mechanisms, i.e. capillary, thermal Marangoni and solutal Marangoni, compete with each other, and lead to diverse droplet dynamics at different stages of evaporation or vapour absorption. The findings shed light on the physical processes within droplets with both positive and negative interfacial mass fluxes, and provide rational explanations for the experimental observations. |
| Databáze: | OpenAIRE |
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