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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

EXPERIMENTAL STUDY OF SESSILE DROPLET BEHAVIOR DURING EVAPORATION: COMPARISON OF METHANOL AND WATER

Get access (open in a dialog) DOI: 10.1615/IHTC16.bae.023654
pages 971-978

Sinopsis

An experimental apparatus is designed and realized in order to analyze the behavior of a sessile drop of two different pure liquids namely methanol and water. The objective is to study separately the behavior of each liquid droplet with the goal of pursuing later the analysis for binary mixtures of the two components. Two experimental techniques are used. One is optical and relies on video recording and image processing and the other one is a thermal technique based on heat flux measurements with a heat flux sensor. Results show very different behavior of the two liquids. Water droplet of 1µL evaporates with a very low kinetics in two distinct stages. During the first one, 80% of the drop volume evaporates with a pinned contact line and lasting for 70% of the droplet lifetime. The second stage consists of evaporation of the 20% remaining liquid with slightly decreasing contact angle and radius. The case of pure methanol seems to be more complicated and more intriguing than that of water. Indeed, for that case, the evaporation kinetics is very fast and instabilities appear during evaporation. 90% of the droplet volume evaporate in the first 25% of the droplet lifetime where the contact line is first pinned then the contact radius decreases sharply. The droplet contracts to form a smaller droplet with a higher contact angle. The capillary effects are substantial and produce instabilities. The remaining 10 % of the volume evaporate in a second step lasting for 75% of the droplet lifetime with decreasing contact angle, height and contact radius until the drop disappears.