Abstract:

To research heterogeneous nucleation of water vapor condensed on the rough surface of the fine particles, a heterogeneous nucleation model was proposed, which based on Fletcher's classical nucleation theory and molecular kinematics theory, considered the effects of surface diffusion mechanism of water vapor molecules, line tension and roughness. The accuracy of the established model was verified by comparing the simulation results of critical supersaturation with the experimental results in existed literature. The effects of line roughness factor and surface roughness factor on critical nucleation free energy, nucleation rate and critical supersaturation were analyzed by numerical simulation. The results show that compared with the fine particles with smooth surface, the microscopic contact angle between the fine particles with rough surface and water vapor is smaller, the wettability of the fine particles is better, and the possibility of heterogeneous nucleation is greater. When the line tension is negative, the rougher the fine particles surface is, the smaller the nucleation free energy and critical supersaturation are, and the higher the nucleation rate is, the more favorable the heterogeneous nucleation of water vapor molecules on the surface of fine particles is. The surface roughness factor has a greater effect on the heterogeneous nucleation and condensation of water vapor on the surface of fine particles than the linear roughness factor.

Key words: fine particle, roughness, water vapor, nucleation, condensation, numerical simulation

摘要：

为研究水汽在细颗粒物粗糙表面上的异质核化特性，基于Fletcher经典核化理论、分子运动学理论等提出了一个考虑水汽分子表面扩散机制、线张力、粗糙度的异质核化模型，并将理论预测的临界过饱和度与已有的实验值进行对比，验证了模型的有效性。采用数值模拟的方法，研究了线粗糙度因子、表面粗糙度因子对临界成核自由能、成核速率、临界过饱和度的影响规律。研究结果表明：与表面光滑的细颗粒物相比，粗糙表面的细颗粒物与水汽间的微观接触角更小，细颗粒物的润湿性更好，更易于发生异质核化凝结；在线张力为负时，细颗粒物的表面越粗糙，其成核自由能和临界过饱和度越小，成核速率越大，有利于水汽分子在细颗粒物表面发生异质核化；表面粗糙度因子比线粗糙度因子对水汽在细颗粒物表面异质核化凝结的影响更大。

关键词: 细颗粒物, 粗糙度, 水汽, 核化, 凝结, 数值模拟