Molecular dynamics study on early stage of filmwise condensation

Filmwise condensation of argon vapor on a platinum surface was studied with molecular dynamics simulation method. An improved molecule supply method was proposed in order to keep the condensation in progress for a comparatively long time. The temporal profiles of local temperature and density were obtained statistically. The results show that the liquid film grows about linearly and there exists an oscillating distribution called 'liquid layering' near the solid wall. The temperature jump at the solid-liquid interface and the temperature gradient in the liquid film were observed. The effects of the vapor temperature and the solid wettability were also studied, and the results indicate that with the increase of the vapor temperature, the temperature gradient, the temperature jump, the thickness of the vapor-liquid interface, the mass flux, and the film growth rate all increase, while the amplitude of the layering region decreases slightly. This indicates that larger temperature difference will strengthen the condensation process, which agrees with the macroscopic phenomenon. The growth rate, the amplitude, and the temperature gradient increase but the temperature jump decreases distinctly when the solid wall becomes more wettable. It can be concluded that the wall neighboring region, where the contact thermal resistance exists, has a dominant effect on the condensation process.