水汽在细微颗粒表面异质核化数值分析

建立蒸汽在同时含有不溶物质与可溶成分的粗糙颗粒表面核化特性数值实验平台,对水汽异质核化晶核形成自由能、成核速率、成核几率、成核临界饱和度、平衡水汽饱和度进行数值分析.结果表明:可溶性盐含量对成核自由能势垒、成核临界饱和度无影响,但对晶核越过自由能势垒进一步长大过程自由能及平衡水汽饱和度影响显著.用自仿射分形理论描述粗糙颗粒表面,将表面粗糙程度与接触角联系起来,研究发现:颗粒表面粗糙度降低了成核自由能势垒,引起成核速率与成核几率迅速增大,成核临界饱和度降低,而对晶核进一步长大过程中水汽的平衡无明显影响.较高的可溶性盐含量有利于核化液滴的长大;颗粒表面越粗糙,越易于核化.

Numerical analysis of water vapor nucleation on fine particles

A numerical experiment platform for vapor nucleation on rough particles containing both insoluble and soluble substances was established.Based on this,the embryo formation free energy,nucleation rate,nucleation probability,critical nucleation saturation and equilibrium water vapor saturation were numerically analyzed.The research results show that neither the free energy barrier of embryo formation nor the critical nucleation saturation is influenced by the mass content of the soluble salt,however both the energy formation free energy and equilibrium water vapor saturation in the further growth of the droplet are greatly influenced.Using self-affine fractal to describe the rough surface of fine particles,the surface roughness is connected with the local contact angle of the particle with water.It is found that because of the roughness of the particle surface,the free energy barrier of embryo formation decreases,thus the nucleation rate and probability of water formation increase dramatically,the critical nucleation saturation decreases,but the particle roughness has no influence on the vapor equilibrium of further growth of the droplet.Higher mass content of the soluble salt favors the growth of the embryo droplet and water vapor is more readily to nucleate on the particle with a higher surface roughness.