Heterogeneous nucleation capability of conical microstructures for water droplets

Abstract

The presence of microstructures on a substrate has a great effect on the heterogeneous nucleation of water droplets. A circular conical apex and a cavity are adopted as the physical model to represent the typical defects which exist widely on substrates, and classic nucleation theory is used to quantitatively analyze the nucleation capability of different microstructures at different condensation conditions. The results indicate that conical cavities with narrower cone angles can reduce the nucleation free energy barrier as compared with apexes and a planar substrate, yielding a relatively higher nucleation capability. With the vapor pressure and supersaturation increasing, the nucleation rate increases rapidly, and some of the cavities that are originally not preferred for nucleation gradually translate into active nucleation sites.Consequently, the activated nucleation sites are finite for practical substrates under certain nucleation conditions, and the nucleation sites number density can be affected by the condensation conditions and the distribution of micro cavities on the substrate. The analysis also indicated that it is possible to realize spatial control of nucleation sites by the construction of micro cavities, and the nucleation sites number density can be intensified by increasing the amount of micro cavities on the substrate.

Comparison of Surface Tension Models for the Volume of Fluid Method

“…The detachment diameter of the bubble [8,9] and shape of rising bubble [10] during bubble evolution in champagne, boiling and electrochemical gas evolution is dependent on surface tension, as is the droplet size produced during atomisation of fuels [11], spraying [12,13] and growth of a bubble in confined geometries [14]. The effect of surface tension is also important in events such as nucleation of bubbles [15,16] and droplets [17].…”

Bioinspired Interfacial Materials with Enhanced Drop Mobility: From Fundamentals to Multifunctional Applications

“…In these systems, the enhancement in the condensation heat and mass transfer could significantly improve system performance, reduce energy costs, and impact economic development. Condensation is dramatically influenced by the physical structure and chemical properties of the solid surface . Depending on the surface wettability, water vapor that condenses on the solid surface exists either in the form of thin films (filmwise) or individual drops (dropwise).…”

Spatial Control of Condensation on Chemically Homogeneous Pillar-Built Surfaces

“…Xu et al conducted an analytical study of the heterogeneous nucleation for conical structures. 44 They found how conical cavities have a lower nucleation free energy barrier compared to apices and planar substrates. We thus believe that the nucleation site density could be locally enhanced and the selectivity between pillars and the surrounding area could be further increased by introduction of micro cavities, or suitable nanotexturing, 11,33,45 on the pillar tops.…”