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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Experimental Investigation of Interfacial Temperature Evolution during Evaporation of Sessile Droplet

Get access (open in a dialog) DOI: 10.1615/IHTC15.mtr.009151
pages 5179-5190

Résumé

A novel method for simultaneous measurement of the evolution of liquid-gas and liquid-solid interface temperatures of an evaporating droplet is presented. A water droplet of nanoliter volume is deposited on top of an infrared transparent glass coated with a non-transparent layer. The temperature of this thin layer is measured via infrared thermography through the transparent glass from below. This temperature is technically identical to the temperature at the liquid-solid interface. Simultaneously the temperature at the liquid-gas interface is measured using a micro thermocouple. This thermocouple is manufactured in-house and has a tip diameter of 13 ?m. The thermocouple is immersed in the droplet to measure the temperature at the apex of the evaporating droplet. To show the functionality of the new method, the temperature evolution during water droplet evaporation on two substrates with different thermal properties has been investigated. The results reveal the dependence of the temperature field evolution and evaporation dynamics on the thermal properties of the substrate. A lower thermal conductivity of the substrate results in a stronger cooling effect of the droplet apex and base which leads to a longer evaporation process. For both substrates the apex is always the coldest point of the droplet, and the three-phase contact line is the warmest. The knowledge of these temperatures helps understanding the evaporation process of a sessile droplet and can validate numerical predictions experimentally.