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Evaporation of sessile droplets of liquid on solid substrates

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posted on 21.07.2014 by Sergey Semenov, Victor Starov, M.G. Velarde, Ramon Rubio
The recent progress in theoretical and experimental studies of simultaneous spreading and evaporation of liquid droplets on solid substrates is discussed for pure liquids including nanodroplets, nanosuspensions of inorganic particles (nanofluids) and surfactant solutions. Evaporation of both complete wetting and partial wetting liquids into a nonsaturated vapour atmosphere are considered. However, the main attention is paid to the case of partial wetting when the hysteresis of static contact angle takes place. In the case of complete wetting the spreading/evaporation process proceeds in two stages. A theory was suggested for this case and a good agreement with available experimental data was achieved. In the case of partial wetting the spreading/evaporation of a sessile droplet of pure liquid goes through four subsequent stages: (i) the initial stage, spreading, is relatively short (1-2 min) and therefore evaporation can be neglected during this stage; during the initial stage the contact angle reaches the value of advancing contact angle and the radius of the droplet base reaches its maximum value, (ii) the first stage of evaporation is characterised by the constant value of the radius of the droplet base; the value of the contact angle during this stage decreases from static advancing to static receding contact angle; (iii) during the second stage of evaporation the contact angle remains constant and equal to its receding value, while the radius of the droplet base decreases; (iv) at the third stage of evaporation both the contact angle and the radius of the droplet base decrease until the drop completely disappears. It has been Cover Letter 2 shown theoretically and confirmed experimentally that during the first and the second stages of evaporation the volume of droplet to power 2/3 decreases linearly with time. The universal dependence of the contact angle during the first stage of evaporation and of the radius of the droplet base during the second stage of evaporation on the reduced time has been derived theoretically and confirmed experimentally. The theory developed for pure liquids is applicable also to nanofluids, where a good agreement with the available experimental data has been found. However, in the case of evaporation of surfactant solutions the process deviates from the theory predictions for pure liquids at concentration below critical wetting concentration and is in agreement with the theory predictions at concentrations above it.

Funding

This work was supported in part by MICINN under grant FIS2012-28231-C02- 01, by ESA under grants FASES and PASTA, COST MP1106 project, and by Engineering and Physical Sciences Research Council, UK, grant EP/D077869/1.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Chemical Engineering

Published in

Understanding Complex Systems

Pages

285 - 300

Citation

SEMENOV, S. ... et al., 2013. Evaporation of sessile droplets of liquid on solid substrates. IN: Rubio, R.G. ... et al. (eds.). Without Bounds : a Scientific Canvas of Nonlinearity and Complex Dynamics. London: Springer, pp. 285-300.

Publisher

© Springer

Version

AM (Accepted Manuscript)

Publication date

2013

ISBN

9783642340697

ISSN

1860-0832

eISSN

1860-0840

Language

en

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