A molecular dynamics study on heat and mass transfer in condensation over smooth/rough surface

Purpose-The purpose of this paper is to focus on the condensation process of hot vapor on smooth/rough walls and find how the condensation film forms and grows. The influences of the roughness and the wettability on condensation are especially analyzed. Design/methodology/approach-The non-equilibrium molecular dynamics simulation method is used to simulate the condensation. In order to maintain the process, a simple and effective molecule insertion mechanics is proposed. Findings-The results show that the wall-neighboring liquid structure becomes more regular with stronger wettability. The temporal parametric profiles show that the condensation does not progress at a constant rate but exhibit obvious unsteady characteristics of gradual deceleration, especially for strong wettability cases. Analysis based on heat and mass transfer indicates that the influence of wettability is quite superior to that of the roughness. The enhancement should be explained by the more fluent and effective energy exchange between solid and liquid particles caused by strong solid-liquid coupling other than by the ordering structure itself. Practical implications-The paper's findings suggest that the wettability should be paid special attention when the heat transfer performance of the microscale condensation is predominantly focused on. Originality/value-The paper provides a vapor-liquid-solid model with molecule insertion. This model can be used to evaluate the contact thermal resistance and the thermal boundary conditions in condensation under different geometric conditions.