Drop spreading and evaporation on a heated substrate under variable gravity conditions

Oleg Kabov, Dmitry Zaitsev, Elizaveta Gatapova, Andrey Semenov, Elena Bykovskaya, Ekaterina Karnauhova, Vladimir Sergeevich Ajaev, Dmitriy Vladimirovich Feoktistov, Genii Kuznetsov

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

In the last decade, evaporation of sessile drops has become an important subject for research in normal gravity and microgravity conditions. We present results of experimental and theoretical studies of the evaporation of a sessile water drop to open atmosphere when the temperature difference between the solid substrate and the atmosphere is up to 50°C. Using substrates with different wettability (Spin Teflon, Spray Teflon, HMDS, Anodized Aluminum) we investigate all three modes of drop evaporation: pinning, partial pinning and depinning. One of the main results is that at the final stage of the drop life the specific evaporation rate increases abruptly, especially for drops with small and moderate contact angle hysteresis (CAH). The data are compared with two types of models. First one is based on thin layer approximation and valid for drops with small contact angles (CA); the second one is a coupled heat and mass transfer quasi-stationary model valid for any CA. The specific evaporation rate calculated from the second model is in good agreement with the experimental data. We also present experimental and theoretical results on the dynamics of sessile water drops, obtained under normal gravity (1g), microgravity (μg) and hypergravity (up to 20g). The microgravity experiments were conducted during the Parabolic Flight campaigns of the European Space Agency. The hypergravity experiment was carried out on the ESA Large Diameter Centrifuge. The objective was to study the effect of the gravity on 1) the shape of a static sessile drop; 2) the dynamic advancing CA in a growing sessile drop. Eleven different smooth and rough surfaces are used, with different CA and different CAH. Water is used as the working liquid. The main variable parameters are: temperature (20-80°C); gravity (μg-20g); drop volume (1μl-5ml); liquid flow rate (0.06-16 ml/min); CA (30-130°). The drop shape is visualized from the top with the help of the Phase Schlieren System, and from the side with the help of the shadow technique with resolution of 6 μm/pix. The spreading of a sessile liquid drop under the influence of gravity has been observed experimentally on surfaces with low CAH. In this case good agreement is obtained between the experiment and modeling. For surfaces with high CAH the contact line is pinned while CA adjusts for different gravity levels. The dynamic advancing CA is found to increase with the gravity.

Original languageEnglish
Title of host publicationProceedings of the 15th International Heat Transfer Conference, IHTC 2014
PublisherBegell House Inc.
Publication statusPublished - 2014
Event15th International Heat Transfer Conference, IHTC 2014 - Kyoto, Japan
Duration: 10 Aug 201415 Aug 2014

Other

Other15th International Heat Transfer Conference, IHTC 2014
CountryJapan
CityKyoto
Period10.8.1415.8.14

Keywords

  • Boiling and evaporation
  • Drops dynamics and evaporation
  • Micro-and hypergravity conditions
  • Two-phase/Multiphase flows

ASJC Scopus subject areas

  • Mechanical Engineering
  • Condensed Matter Physics

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    Kabov, O., Zaitsev, D., Gatapova, E., Semenov, A., Bykovskaya, E., Karnauhova, E., Ajaev, V. S., Feoktistov, DV., & Kuznetsov, G. (2014). Drop spreading and evaporation on a heated substrate under variable gravity conditions. In Proceedings of the 15th International Heat Transfer Conference, IHTC 2014 Begell House Inc..