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    The contact angle of nanofluids as thermophysical property

    Year: 2019

    Journal: J. Colloid Interface Sci., Volume 547, JUL 1, page 393–406

    Authors: Hernaiz, M.; Alonso, V; Estelle, P.; Wu, Z.; Sunden, B.; Doretti, L.; Mancin, S.; Cobanoglu, N.; Karadeniz, Z. H.; Garmendia, N.; Lasheras-Zubiate, M.; Hernandez Lopez, L.; Mondragon, R.; Martinez-Cuenca, R.; Barison, S.; Kujawska, A.; Turgut, A.; Amigo, A.; Huminic, G.; Huminic, A.; Kalus, M-R; Schroth, K-G; Buschmann, M. H.

    Organizations: COST (European Cooperation in Science and Technology)European Cooperation in Science and Technology (COST) [CA15119 NANOUPTAKE]; Bundesministerium fur Wirtschaft and Energie (Germany) [49VF 170005]; European Union through the European Regional Development Fund (ERDF); Ministry of Higher Education and ResearchMinistry of Higher Education & Scientific Research (MHESR); French region of Brittany; Rennes Metro poleRegion Bretagne; Spanish Ministry of Economy and Competitiveness [ENE2014-55489-C2-1-R, ENE2017-86425-C2-2-R]; UE FEDER programme [ENE2014-55489-C2-1-R, ENE2017-86425-C2-2-R]

    Keywords: Round robin test; Contact angle; Nanofluids; Influence of volume; Influence of temperature; Experimental strategy

    Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids - suspensions containing nanometre-sized particles - can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume as a thermophysical property to characterise nanofluids positioned on a certain substrate under a certain atmosphere. Graphene oxide, alumina, and gold nanoparticles are suspended in deionised water. Within the framework of a round robin test carried out by nine independent European institutes the contact angle of these suspensions on a stainless steel solid substrate is measured with high accuracy. No dependence of nanofluids contact angle of sessile droplets on the measurement device is found. However, the measurements reveal clear differences of the contact angle of nanofluids compared to the pure base fluid. Physically founded correlations of the contact angle in dependency of droplet temperature and volume are obtained from the data. Extrapolating these functions to zero droplet volume delivers the searched limiting contact angle depending only on the temperature. It is for the first time, that this specific parameter, is understood as a characteristic material property of nanofluid droplets placed on a certain substrate under a certain atmosphere. Together with the surface tension it provides the foundation of proper modelling phase change heat transfer processes of nanofluids. (C) 2019 Published by Elsevier Inc.
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