纳米结构影响沸腾换热特性的分子动力学模拟

Molecular dynamics simulation of the effect of nanostructure on the heat transfer characteristics of pool boiling

采用分子动力学方法模拟液体在纳米结构表面的快速沸腾过程.主要研究了纳米结构表面粗糙度以及栏栅形和棋盘形两种排列方式对液体快速沸腾过程以及换热特性的影响.研究结果表明,随着纳米结构表面粗糙度的增加,栏栅形和棋盘形纳米结构表面液体沸腾起始时间均提前.当栏栅形和棋盘形纳米结构表面粗糙度相同时,棋盘形纳米结构表面会进一步缩短液体沸腾起始时间.形成这种现象的原因是纳米结构表面粗糙度的增加,增加了固液接触面积,提高了初始时刻热通量,减小了固液界面热阻,导致表面附近液体动能增大,增大了液体高度方向的温度梯度,有利于液体发生沸腾.当纳米结构表面粗糙度相同时,棋盘形纳米结构表面具有较小的界面热阻,从而缩短了沸腾所需要的时间.

The molecular dynamics method is used to simulate the rapid boiling process of the liquid on the surface of the nanostructure. The effects of the surface roughness of the nanostructure and both the fence-shaped and checkerboard-shaped arrangements on the rapid boiling process and heat transfer characteristics of the liquid were mainly studied. The research results show that with the increase of the surface roughness of the nanostructures, the onset time of the liquid boiling of the fence-shaped and checkerboard-shaped nanostructures is advanced. When the surface roughnesses of the fence-shaped and checkerboard-shaped nanostructures are the same, the surface of the checkerboard-shaped nanostructures will further shorten the liquid boiling start time. The reason for this phenomenon is that the surface roughness of nanostructures increases the solid-liquid contact area and the heat flux at the initial moment, and reduces the thermal resistance of the solid-liquid interface, resulting in the increases of kinetic energy near the surface and hence of the temperature gradient along the height of the liquid. When the surface roughness of the nanostructure is the same, the surface of the checkerboard-shaped nanostructure has a smaller interface thermal resistance, thereby shortening the time required for boiling.