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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Effect of Marangoni Flow on the Evaporation Rate of Sessile Droplets

Dinghua Hu
MIIT Key Laboratory of Thermal Control of Electronic Equipment, Nanjing University of Science and Technology, Nanjing, 210094, China

Huiying Wu
Shanghai Jiao Tong University, 800 Dong Chuan Rd. Minhang District, Shanghai 200240, China

Zhenyu Liu
Shanghai Jiao Tong University, 800 Dong Chuan Rd. Minhang District, Shanghai 200240, China

DOI: 10.1615/IHTC15.evp.009419
pages 2457-2469


KEY WORDS: Boiling and evaporation, Numerical simulation and super-computing, Thermophysical properties, Marangoni flow, Evaporation rate, Sessile droplets, Contact angle, Substrate temperature

Abstract

The Marangoni flow generated by the surface tension gradient plays an important role in the evaporative dynamics of sessile droplets. The effect of the Marangoni flow on the evaporation rate of sessile droplets, which was not fully understood in previous studies, is numerically analyzed in this paper. A numerical model with the Marangoni effect considered is developed to describe the evaporation process of sessile droplets. The vapor concentration field, the fluid velocity field and the temperature field are numerically simulated with the finite method (FEM). The roles of contact angle and substrate temperature on the contribution of Marangoni flow to the evaporation rate are investigated. Numerical results show that the contribution of Marangoni flow to the evaporation rate of droplets increases with the contact angle, and its increasing rate increases with the substrate temperature. The Marangoni flow increases the evaporation rate of a hemispherical droplet (i.e. contact angle is 90º) by 5% for a substrate temperature of 25ºC (equal to the ambient temperature) and by 24.5% for a substrate temperature of 55 ºC, respectively. The findings in this work prove that the contribution of Marangoni flow to the evaporation rate cannot be neglected for droplets with a larger contact angle on a hot substrate, which extends the understanding of evaporative dynamics of sessile droplets.

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