Dependences of Formation and Transition of the Surface Condensation Mode on Wettability and Temperature Difference

JH Pu and J Sun and Q Sheng and W Wang and HS Wang, LANGMUIR, 36, 456-464 (2020).

DOI: 10.1021/acs.langmuir.9b03339

In this work, we use molecular dynamics (MD) simulations to investigate the dependences of formation and transition of surface condensation mode on wettability (beta) and vapor-to-surface temperature difference (Delta T). We build a map of different surface condensation modes against beta and Delta T based on plenty of MD simulation results and reveal five formation mechanisms and two transition mechanisms. At low beta and Delta T, the high free energy barrier (Delta G*) prevents any surface clusters from surviving, therefore no-condensation (NC) is observed. The formation of dropwise condensation (DWC) could evolve from either nucleation or film rupture. Similarly, the formation of filmwise condensation (FWC) could evolve from either nucleation or the adsorption-induced film. The transition between NC and DWC is determined by Delta G* according to classical nucleation theory. The transition between DWC and FWC depends on the stability of condensate film; there emerges the competition between the trend that the uneven condensate film contracts and ruptures to droplets favored by lower beta and the trend that the uneven condensate film continues growing promoted by higher Delta T. We finally present a schematic overview of all of the mechanisms revealed for a better understanding of the physical phenomenon of the surface condensation mode.

Return to Publications page