Abstract
We use molecular dynamics simulation to investigate the early and developed stages of surface condensation. We find that the liquid-vapor and solid-liquid interfacial thermal resistances depend on the properties of solid and fluid, which are time-independent, while the condensate bulk thermal resistance depends on the condensate thickness, which is time-dependent. There exists intrinsic competition between the interfacial and condensate bulk thermal resistances in timeline and the resultant total thermal resistance determines the condensation intensity for a given vapor-solid temperature difference. We reveal the competition mechanism that the interfacial thermal resistance dominates at the onset of condensation and holds afterwards while the condensate bulk thermal resistance gradually takes over with condensate thickness growing. The weaker the solid-liquid bonding, the later the takeover occurs. This competition mechanism suggests that only when the condensate bulk thermal resistance is reduced after it takes over the domination can the condensation be effectively intensified. We propose a unified theoretical model for the thermal resistance analysis by making dropwise condensation equivalent to filmwise condensation. We further find that near a critical point (contact angle being ca. 153°) the bulk thermal resistance has the least opportunity to take over the domination while away from it the probability increases.
Highlights
Our recent work[3], focused on the onset of surface condensation by molecular dynamics simulation and classical nucleation theory, has revealed the intrinsic connection between dropwise condensation (DWC) and filmwise condensation (FWC)
We reveal that the competition between the interfacial and condensate bulk thermal resistances determines the characteristics of time evolutions of different condensation modes and further the condensation intensities
Based on the ideally spherical crown for a single droplet on solid surface, the surfaces I and II are the isothermal surfaces and the distance between the two surfaces is the local thickness of the condensate bulk thermal resistance
Summary
Our recent work[3], focused on the onset of surface condensation by molecular dynamics simulation and classical nucleation theory, has revealed the intrinsic connection between DWC and FWC. The solid wall (blue) applied at the sides and the diffuse reflection boundary is applied at the top end. We reveal that the competition between the interfacial and condensate bulk thermal resistances determines the characteristics of time evolutions of different condensation modes and further the condensation intensities. The formation and transition mechanisms revealed in our previous work[3] presents the spatial characteristics of unification of surface condensation while the competition mechanism revealed in this work presents its temporal characteristics. These characteristics clarify a fundamental insight of the phenomenon of surface condensation
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have