Abstract:

The effects of surface structure and wettability on the heat transfer performance of pool boiling between liquid and solid wall were investigated from the nano scale by molecular dynamics method. The solid wall consists of smooth surface, concave and convex hemispherical nanostructure surface.The wettability between liquid and solid wall ranged from super hydrophilic to super hydrophobic. The changes of liquid layer morphology, temperature and heat flux of liquid argon on the three solid wall surfaces during heating were illustrated. The results showed that the boiling process of liquid argon layer could be roughly divided into two heating stages. One stage was that the liquid argon layer was adsorbed on the solid surface, and the other stage was that the liquid argon layer was separated from the wall. In the first stage, the increase of argon layer temperature, heat flux and the generation rate of gaseous argon atoms were greater than those in the second stage. There were obvious inflection points in the changes of argon layer temperature, heat flux and the amount of gas argon on the hydrophilic surface, while there was little difference in the two-stage heating process of the hydrophobic surface. The concave and convex hemispherical nanostructures on the hydrophilic surface promoted the generation of bubbles and the changes of temperature and heat flux. However, the concave and convex hemispherical nanostructures on the hydrophobic and superhydrophobic surface had different influences on generation of bubbles and temperature and heat flux. The calculation results provided a theoretical basis for pool boiling heat transfer and microstructure selection.

Key words: wettability, nanostructure, boiling, heat transfer, molecular dynamics simulation

摘要：

为了从纳米尺度了解表面结构和润湿性对池沸腾液体与固体壁面的传热性能，本文采用分子动力学方法研究了超亲水至超疏水不同润湿性的液体氩在光滑表面和含凹、凸半球纳米结构表面的沸腾传热过程，分析了三种表面上液氩在受热过程的形态、温度、热流密度等相关参数的变化情况。结果表明，液氩层沸腾过程大致可分为液氩层吸附于固体表面和液氩层从壁面脱离两个加热阶段，当液氩层吸附于固体表面时，温度升高、热流密度及气态氩原子产生速度均大于液氩层脱离壁面时的情况，在这两个阶段亲水表面上氩原子温度变化有明显的拐点，而疏水表面在两个阶段加热过程相差不大。亲水表面上的微结构能吸附更多液氩原子，促进了气泡产生及加速温度、热流密度的变化，而在疏水及超疏水微结构表面，微纳结构与液氩间的气膜层促进了气泡产生，计算结果为池沸腾传热及微结构选择提供了理论依据。

关键词: 润湿性, 纳米结构, 沸腾, 传热, 分子动力学模拟