Abstract 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.

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纳米狭缝蒸发的分子动力学研究：狭缝几何形状和润湿性的影响

摘要 液-汽相变是一种有效的热能传递过程，已在许多工业应用中得到应用。为了增强液-气相变传热，纳米工程材料，如纳米结构表面，迄今已进行了实验和数值研究。然而，低估纳米结构表面影响蒸发的方式和程度还不够。在本研究中，我们采用了流体分子最初停留在其中的纳米狭缝系统，并通过经典分子动力学模拟，数值研究了流体分子如何从纳米狭缝蒸发，这取决于纳米狭缝的几何形状和表面润湿性。在固体表面与流体液相接触的情况下，分子行为发生了变化，尤其是在固体壁附近。一些流体分子经常与气液界面发生多次碰撞。我们将分子行为与反射区分开来，并将其新定义为保留。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，增加了沿着侧壁移动的蒸发分子的量。这是因为固体壁附近的分子间电位低。当侧壁的润湿性不同时，流体分子被吸引到更亲水的侧壁。这导致气液界面更接近狭缝边界。