Molecular dynamics simulation of evaporation coefficient of vapor molecules during steady net evaporation in binary mixture system
Molecular dynamics simulation of evaporation coefficient of vapor molecules during steady net evaporation in binary mixture system
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DOI：
10.1016/j.ijheatmasstransfer.2022.122663
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发表时间：
2022-02-11
影响因子：
5.2
通讯作者：
Watanabe, Masao
中科院分区：
文献类型：
--
作者：
Tabe, Hirofumi;Kobayashi, Kazumichi;Watanabe, Masao
在这项研究中，利用分子动力学模拟，在汽-气二元混合物和非平衡系统中计算了代表蒸汽分子蒸发速率的蒸发系数。这里的非平衡是指蒸气分子发生净蒸发的状态，计算系统由蒸气分子和不凝性(NC)气体分子组成。证明非平衡状态下的蒸发系数与平衡状态下的蒸发系数几乎相同。气液界面周围的NC气体分子的数密度与由于分子碰撞而阻止蒸气分子蒸发的概率有关，并且与系统状态无关。这使得无论系统处于平衡还是非平衡，蒸发系数都相同。相反，随着NC气体分子摩尔分数的增加，蒸发系数降低。摩尔分数的增加导致气液界面周围NC气体分子的数密度更高，导致分子碰撞次数增加，从而阻止蒸气分子蒸发。此外，还发现NC气体分子的存在引起的界面结构的变化会影响蒸发蒸气分子的速度分布。 (c) 2022 作者。由 Elsevier Ltd 出版。这是一篇遵循 CC BY-NC-ND 许可证的开放获取文章 ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
In this study, an evaporation coefficient representing the evaporation rate of vapor molecules was calculated in a vapor-gas binary mixture and non-equilibrium system using molecular dynamics simulation. The non-equilibrium herein refers to a state in which the net evaporation of vapor molecules occurs, and the calculation system is composed of vapor molecules and non-condensable (NC) gas molecules. The evaporation coefficient in the non-equilibrium state was demonstrated to have almost the same value as that in the equilibrium state. The number density of NC gas molecules around the gas-liquid interface, which is related to the probability that vapor molecules are prevented from evaporating owing to molecular collisions, is shown to be independent of the system state. This makes the evaporation coefficient the same regardless of whether the system is in equilibrium or non-equilibrium. In contrast, the evaporation coefficient decreased as the molar fraction of the NC gas molecules increased. The increase in the molar fraction causes a higher number density of NC gas molecules around the gas-liquid interface, leading to an increase in the number of molecular collisions, which prevents vapor molecules from evaporating. Moreover, it was clarified that the change in the interface structure caused by the presence of NC gas molecules affects the velocity distribution of evaporation vapor molecules. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )