Capillary condensation model within nano-scale pores studied with molecular dynamics simulation
Capillary condensation model within nano-scale pores studied with molecular dynamics simulation
复制标题
通过分子动力学模拟研究纳米级孔隙内的毛细管冷凝模型
DOI：
10.1252/jcej.30.274
复制
发表时间：
1997
影响因子：
0.8
通讯作者：
M. Okazaki
中科院分区：
文献类型：
--
作者：
Tomohisa Yoshioka;M. Miyahara;M. Okazaki
提出了一种新的纳米尺度毛细凝聚模型。模型中考虑了孔壁势对冷凝现象的影响。该模型可以将冷凝相形成的临界相对压力与孔隙尺寸联系起来。还考虑了表面张力的曲率依赖性。这是一个基于流体静力学分析的新模型，其特点是由孔壁施加的势场引起的凝结相的不均匀性。我们进行了吸附模拟狭缝状孔的范围内的2-4 nm的宽度，通过使用分子动力学（MD）方法。在模拟中，吸附状态的平衡蒸气压能够通过计算从孔解吸并到达具有假想蒸气相的边界平面的吸附物颗粒的数量来计算。我们使用类氩LJ颗粒作为吸附质，吸附剂由LJ类碳壁组成。对于不同的孔隙宽度，我们模拟的吸附现象，得到的吸附平衡关系，从表面吸附在孔壁在低相对压力下的状态下，在高相对压力下的冷凝状态。因此，显着的差异，毛细冷凝的临界相对压力从Kelvin模型预测的值被重申，而所提出的模型预测以及在纳米尺度的孔冷凝的临界相对压力。还从凝析油界面形状和凝相压力分布等方面验证了该模型的有效性，并取得了较好的一致性。
A new capillary condensation model for nano-scale pores is proposed. The effect of the pore wall potential on the condensation phenomenon was considered in the model. The critical relative pressure at which the condensation phase is formed can be related to the pore size by the model. The curvature dependency of the surface tension was also taken into account. This is a new model based on hydrostatic analysis, and its feature is non-uniformity of the condensation phase caused by the potential field exerted by the pore walls. We carried out adsorption simulations within slit-like pores in the range of 2-4 nm in width by using a Molecular Dynamics (MD) method. In the simulations, equilibrium vapor pressure for an adsorbed state was able to be calculated by counting the number of adsorbate particles which desorbed from the pore and reached a border plane with imaginary vapor phase. We used argon-like LJ particles as the adsorbate and the adsorbent consisted of LJ carbon-like walls. For various pore widths, we simulated the adsorption phenomena to obtain the adsorption equilibrium relation, from the state of the surface adsorption on a pore wall under a low relative pressure to the state of the condensation under a high relative pressure. Consequently, significant discrepancy in the critical relative pressure for capillary condensation from the value predicted by the Kelvin model was reaffirmed, while the proposed model predicted well the critical relative pressure for condensation in nano-scale pores. The validity of the proposed model was examined also from the aspects of the shape of gas-condensate interface and pressure distribution in the condensed phase, and gave fairly good agreement.