Supersaturations S * (at which unlimited condensation starts) than ANT. WhenĮxperimental contact angles are used, CNT predicts higher critical The premise of CNT is that liquidĭroplets appear on the surface once the vapor becomes supersaturated. Reflected in the values of the FHH parameters A and B that are obtained from experimental adsorption equilibria. Surface at subsaturation, and the molecular nature of adsorption is ANT is based on the premise that vapor molecules are already adsorbed on the Malila, 2016), accounts for water adsorption prior to the onset of heterogeneousįigure 1 (a) A schematic showing the principal differences between ANT andĬNT. The adsorption nucleation theory, ANT (Laaksonen, 2015 Laaksonen and Hinder a quantitative description of heterogeneous nucleation. Process of water adsorption omits important physics that may With increasing adsorption layer thickness (Hill, 1949a). Of adsorbed water differs considerably from what is implied by the single In reality, water already adsorbs to the surface under subsaturated conditions (relative humidity below 100 %), which can play a critical role in the nucleation process. Surface and the nucleating droplet are expressed by one parameter – theĬontact angle (Fletcher, 1958). Water on surfaces prior to the formation of a macroscopic droplet (Fig. 1a).Īnother shortcoming is that all of the energetics of interaction between the Nucleation in atmospheric and climate models on their own – and are impractical forĪ shortcoming of CNT is that it does not recognize the existence of any Reveal aspects of heterogeneous nucleation phenomena, but theyĬannot provide a theoretical framework for describing heterogeneous Molecular simulations (Lupi et al., 2014) are able to Provide notoriously poor predictions of water drop nucleation (Mahata andĪlofs, 1975). Variants of classical nucleation theory, CNT (Fletcher, 1958), which Large uncertainty regarding the role of aerosol–cloud interactions in theĬlimate system (Seinfeld et al., 2016). Provides quantitative comprehension of the process, and it translates into This poor understanding isĮxpressed by the lack of an established heterogeneous nucleation theory that Remains poorly understood, even after more than a century of research Industrial processes (e.g., dropwise condensation), biological systems (e.g., infection strategy of plant pathogens), everyday situations (e.g., fogging of glasses and windshields), and fundamentally important atmospheric phenomena (clouds, frost, and hoar frost) are all driven by the heterogeneous nucleation of water (Pruppacher and Klett, 1997 Franks, 2003).ĭespite its ubiquity and importance, the heterogeneous nucleation of water vapor External surfaces can facilitate the phase transition via a process known as heterogeneous nucleation. When water vapor becomes supersaturated – i.e., its relative humidity exceeds 100 % – it is in a metastable state and can form liquid water or ice.
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