Molecular dynamic study of evaporation in nanoslit: Influence of slit geometry and wettability
Molecular dynamic study of evaporation in nanoslit: Influence of slit geometry and wettability
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DOI：
10.1016/j.ijheatmasstransfer.2020.120463
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发表时间：
2020-12
影响因子：
5.2
通讯作者：
Y. Ueki;Hideaki Murashima;M. Shibahara
中科院分区：
文献类型：
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作者：
Y. Ueki;Hideaki Murashima;M. Shibahara
液-汽相变是传递热能的有效过程，并已在许多工业应用中得到利用。为了强化液-汽相变传热，纳米材料，如纳米结构表面，已经被实验和数值模拟研究到目前为止。然而，了解纳米结构表面如何以及在多大程度上影响蒸发是不够的。在本研究中，我们采用了纳米缝系统，其中流体分子最初停留，并通过经典的分子动力学模拟，数值研究了如何从纳米缝中蒸发的流体分子，这取决于纳米缝的几何形状和表面润湿性。当固体表面与流体的液相接触时，分子行为发生变化，尤其是在固体壁附近。一些流体分子频繁地多次与气液界面碰撞。我们将分子行为与反射区分开来，并将其重新定义为保留。在本研究中，发现随着固体侧壁变得更加亲水，侧壁表面上的分子的流动性变得更高，增加了蒸发分子沿沿着行进的量。这是因为固体壁附近的分子间势较低。当侧壁的润湿性不同时，流体分子被吸引到更亲水的侧壁。这使得气液界面更靠近狭缝边界。如果气-液界面和狭缝边界之间的距离相对较短，则气-液界面附近的滞留量减少。
A liquid-vapor phase change is an efficient process to transfer thermal energy and has been utilized in much industrial application. To enhance the liquid-vapor phase-change heat transfer, nanoengineered materials, such as nanostructured surface, have been experimentally and numerically investigated so far. Nevertheless, understating how and how much the nanostructured surfaces influence evaporation has not been sufficient. In the present study, we employed the nanoslit systems, inside which fluid molecules initially stayed, and by means of classical molecular dynamics simulations, numerically investigated how the fluid molecules evaporated from the nanoslits, depending on the geometry and the surface wettability of the nanoslits. In the presence of the solid surface in contact with the liquid phase of the fluid, the molecular behaviors changed, especially in the vicinity of the solid wall. Some of the fluid molecules frequently collided with the gas-liquid interface at multiple times. We distinguished the molecular behavior from the reflection, and newly defined it as the retention. In the present study, it was found that, as the solid sidewall became more hydrophilic, the mobility of the molecules on the sidewall surface became higher, increasing the amount of the evaporation molecules traveling along the sidewalls. It was because the intermolecular potential was low in the vicinity of the solid walls. When the wettability of the sidewalls differed, the fluid molecules were attracted to the more hydrophilic sidewall. It caused that the gas-liquid interface got closer to the slit boundary. If the distance between the gas-liquid interface and the slit boundary was relatively short, the amount of the retention near the gas-liquid interface decreased.