Numerical investigation of effects of curvature and wettability of particles on heterogeneous condensation

The incipient process of water vapor condensation around an insoluble nanoscale particle is studied by a molecular dynamics method, and the emphasis is placed on the effects of particle surface curvature and wettability. With a high initial saturation, two different linear nucleation stages are observed. At the first stage, clusters are formed by the water molecules adsorbed on the surface such that the nucleation rate is significantly affected by both water molecule flux toward the surface and adsorption probability. The former decreases with the surface curvature, and the latter is in proportion to the wettability. At the second stage, the nucleation rate is enhanced by the contribution of homogeneous clusters adsorbed to the surface and reduced by cluster merging because of the space limitation on small particles. As a result, the nucleation rate is basically not affected by the particle size. The average size of clusters keeps constant for a while, then starts to grow with a gradually increased growth rate. It is concluded that both curvature and wettability of the particle surface promote the cluster growing.