Droplet Evaporation Dynamics of Low Surface Tension Fluids Using the Steady Method


Gunay A. A. , Gnadt M., Sett S., Vahabi H., Kota A. K. , Miljkovic N.

LANGMUIR, vol.36, no.46, pp.13860-13871, 2020 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 36 Issue: 46
  • Publication Date: 2020
  • Doi Number: 10.1021/acs.langmuir.0c02272
  • Journal Name: LANGMUIR
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Biotechnology Research Abstracts, Chemical Abstracts Core, Chimica, Compendex, EMBASE, INSPEC, MEDLINE
  • Page Numbers: pp.13860-13871
  • Middle East Technical University Affiliated: No

Abstract

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 <= R-b <= 260 mu m), apparent advancing contact angle (45 degrees <= phi(a,app) <= 162 degrees), surface temperature (30 < T-s < 60 degrees C), and relative humidity (40% < phi < 60%). Following validation, evaporation of ethanol (approximate to 22 mN/m), hexane (approximate to 18 mN/m), and dodecane (approximate to 25 mN/m) were studied for 90 <= R-b <= 400 mu m and 10 < T-s < 25 degrees 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.