Effects of gradient and patterned wetting configuration on condensation over hybrid wetting surface from atomistic viewpoint

Abstract

In this study, atomistic simulations have been conducted in order to illustrate the effects of gradient and patterned wetting configurations on nanoscale condensation over hybrid wetting surfaces. To pursue this objective, a three-phase argon-platinum atomistic system has been modeled, consisting of two solid surfaces and two different phases of argon atoms. Following the necessary equilibration of the atomistic system at 90 K, the temperatures of the upper and lower surfaces are maintained at 130 K and 90 K, respectively, to make them serve as evaporating and condensing surfaces. The wetting characteristic of the lower surface is kept unchanged in all of the cases to corroborate the uniform evaporating condition, while that of the condensing wall has been changed to follow two major classes, namely, gradient and patterned wetting profiles. Functionally gradient wetting (FGW) surfaces have been modeled utilizing the power-law function from the notion of functionally graded material (FGM), whereas patterned wetting surfaces are modeled by juxtaposing the regions of different wettability. The condensation characteristics of different surfaces are reported with important parameters such as nucleation rate, cluster growth and coalescence, thermal resistance at the solid–liquid interface, condensed fluid atoms, mass flux of the condensate, condensing wall heat flux, and surface tension profile. The simulation results have revealed that an increased proportion of hydrophilic atoms enhances the condensation heat transfer. In addition, FGW surfaces have been found to be better than patterned ones in terms of condensation heat transfer enhancement.