Rupture of evaporation liquid films heated from below and subject to thermocapillarity
Yeo, Veronica Xiao Yun
Date of Issue2016-05-26
School of Mechanical and Aerospace Engineering
Evaporating thin liquid films on a solid surface are encountered in many mechanical, chemical, nuclear engineering applications and processes such as cooling, lubrication, coating and cleaning. Hence, it is important for the liquid film to remain intact till it dries out. Therefore, this study investigates the experimental results of a thin liquid film rupture of ethanol on heated substrate of different materials, PMMA and glass. Using a high speed camera, two methods of creating a thin ethanol film were discovered. Marangoni effects due to surface tension gradient and mass lost through evaporation have resulted in receding contact line and the expansion of rupture region. The positions of the ruptures were random and only contact line receding is observed for temperature 50°C and above. Initial ruptures to expand to 1mm were recorded and it is found out that ruptures on PMMA test plate took more than 1 second. On the glass test plate, ruptures took less than 1 second to grow to 1 mm. In addition, study of hydrothermal waves and thermocapillary instabilities of thin fluid layers in a rectangular geometry through the design of a rectangular slot with adjustable depth. Future investigations can be done on substrates with coating and different volatile fluids using a thermostat for easy manipulation of temperatures.
Final Year Project (FYP)
Nanyang Technological University