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ABSTRACT
This paper deals with the modeling of dropwise condensation process on a wettability gradient surface. The proposed heat transfer model explicitly takes into account the mechanical nonequilibrium on the periphery of the droplet due to the surface-energy gradient and the contact-angle hysteresis. The model aims to predict the dynamic behavior of a droplet placed on a wettability gradient surface regarding the temperature difference between the wall and the saturated vapor. A comprehensive analysis of all the contributing thermal resistances is proposed. The influences of contact angle, temperature difference, and other representative parameters on a single droplet on a horizontal surface are also discussed. The results indicate that a wettability gradient can cause a reduction of the mean size of the droplets on the condensing surface and thus enhance significantly the heat transfer rate.
Funding
It is gratefully acknowledged that financial support for this work has been provided in part by the European Space Agency, Microgravity Application Program “MANBO” (Multiscale ANalyses of BOiling).
Additional information
Notes on contributors
Felipe M. Mancio Reis
Filipe M. Mancio Reis has been a postdoctoral researcher at LAPLACE, France, since 2014. He obtained his Ph.D. in energetics and transfers in 2014 from the University of Toulouse. He received in 2011 a Diploma of Engineer in mechanics and energetics from Polytech' Marseille, Marseille, France. He is currently working on passive heat transfer enhancement techniques and two-phase cooling systems.
Pascal Lavieille
Pascal Lavieille has been an assistant professor in the LAPLACE Laboratory, University Paul Sabatier of Toulouse, France, since 2002. He obtained his Ph.D. in 2001 from the University H. Poincaré in Nancy, France. He is a specialist in optical diagnostics for the determination of temperatures fields and measurement of film thickness. His research interests are focused on phase change in microchannels.
Marc Miscevic
Marc Miscevic has been an associate professor at LAPLACE, Toulouse University, France, since 1999. Prior to coming to LAPLACE, he obtained his Ph.D. in 1997 from the Université de Provence in Marseille, France. He is involved in research in the areas of active methods of heat transfer enhancement, phase change in microchannels and microgravity (condensation, boiling, capillary phenomena, wettability), and two-phase cooling systems.