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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

INFLUENCE OF SUBSTRATE TEMPERATURE ON MARANGONI CONVECTION INSTABILITY IN AN EVAPORATING SESSILE DROPLET AT CONSTANT CONTACT LINE MODE

Get access (open in a dialog) DOI: 10.1615/IHTC16.cov.022860
pages 3053-3060

Abstract

Marangoni convection in an evaporating sessile droplet of silicone oil (0.65cSt) was experimentally investigated at constant contact line mode. A series of experiments were carried out in a wide range of the temperature of substrate in order to investigate the influence of temperature of substrate on Marangoni convection instability. We found that the convection in the evaporating sessile droplet when the temperature of substrate (Tw) is higher than ambient temperature (Ta) is different from that when Tw is lower than Ta. Three kinds of convection are observed with the droplet evaporating when Tw is higher than Ta, i.e., steady thermocapillary convection, steady Bénard-Marangoni (BM) convection and unsteady BM convection respectively. Hydrothermal waves (HTWs) are observed in the sessile droplet and the coexistence of HTWs and BM convection cells can also be investigated when Tw is lower than Ta. The critical contact angle for the onset of them are revealed through our experiments and we find that the critical contact angle increases with the increase of Tw when Tw is higher than Ta. With the increase of Tw, the number of Bénard-Marangoni convection cells increases during the stage of steady BM convection.