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Influence of surface wettability on pool boiling onset

The miniaturization of electronic components and their always increasing integration, with the fascinating perspective of micro-robots, micro- and nano-systems for sensors and fluid manipulation, drives various and important technological advancements. Thermal management in micro- and nanoscale systems is currently a bottleneck in the further development of these technologies. Among the different ways to remove this big amount of heat, phase-change heat transfer seems to be one of the most efficient. It permits to obtain significant heat fluxes, spreading the heat from hot spots to larger heat sinks. Even if they are efficient, these systems present some drawbacks such as the gravity dependence or the superheat temperature at the onset of boiling, for example. Nowadays, one of biggest challenge is to reduce as much as possible the superheat temperature needed to reach the boiling. The influence of surface wettability on boiling onset has been argued since decades, but up to now it was difficult to understand and measure this single effect due to the dominant and apparently inextricable role of the surface roughness and the cavity distribution on the surface. In fact most of the boiling onset models are still addressing the critical role of cavity size and surface tension for the initial appearance of nucleation sites. We have perfomed a series of experiments on ultra-smooth surfaces with and without a highyl resistant grafted monolayer. The results obtained show that a decrease of the surface wettability allows to achieve boiling in an easier way. This has been quantified by the acquisition of boiling curves and by image analysis, for a wide range of wettabilities, on metallic and glass substrates. A novel theoretical approach, based on MD simulations, is proposed.

Marco Marengo, Professor of Thermal Engineering at the University of Brighton, UK, is a physicist with specific interests in heat and mass transfer, fluid mechanics, two-phase systems, heat pipes, liquid interfaces, physics of drops and sprays, surface wettability, CFD simulations and thermal simulations. Prof. Marco Marengo achieved a Master Degree in Physics cum laude at the University of Turin on Dynamical Systems. In 1993, started the Ph.D. studies at the Polytechnic of Milan. Awarded by the Deutscher Akademischer Austauschdienst and by the EU Marie Curie Program, he joined the Institut of Fluidmechanics of Prof. Durst in Erlangen. In 1996 he got a Ph.D. in Energetics at the Polytechnic of Milan with a thesis about “Drop Impingement on Liquid Film”. Associate Professor of Thermal Physics from 2002 too 2016 at the University of Bergamo. In 2014 he was appointed as Professor of Thermal Engineering at the University of Brighton, joining the Center of Automotive Engineering. He is member of the Space Environment Advisory Committee of the UK Space Agency. He is a member of various International Conference Scientific Committees and Editorial Boards of International Journals. He is one of the few European "frequent flyers" of the ESA Parabolic Flight Campaigns. He is a Visiting Professor at the Laboratoire de Physique des Surfaces et des Interfaces, University of Mons, Belgium, at the University of Toronto and York University in Toronto, Canada. He delivered more than 30 invited lectures around the world. From 2009 to 2018 he has been European Editor of the International Journal "Atomization & Sprays” and since 2016 he is the UK permanent representative in the Committee of International Heat Pipe Conference and International Heat Pipe Symposium. He was co-founder of two spin-off companies. Prof. Marengo is co-director of the International Advanced Course of Liquid Interfaces, Drop and Spray Systems. He is a member of the Center for Innovation, Technology and Policy Research - IN+, Instituto Superior Técnico, Lisbon, Portugal. He has published more than 300 papers, among which 80 papers in peer-reviewed international journals and 7 patents. Presently, he is the Chair of the Professoriate Advisory Group of the University of Brighton.