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MOLECULAR DYNAMICS STUDY ON MASS TRANSFER AT LIQUID-VAPOR INTERFACE AND EXPERIMENTAL VERIFICATION USING CAIRALLY SPACE

液-汽界面传质分子动力学研究及CAIRALLY空间实验验证

基本信息

批准号：
11650228
负责人：
TSURUTA Takaharu
金额：
$ 2.37万
依托单位：
KYUSHU INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Water is an important material in the field of the thermal engineering. In this research, condensation and reflection characteristics of water molecules at liquid-vapor interface were examined using the molecular dynamics method. Also, the non-equilibrium evaporation experiment was carried out, and the measured interfacial mass transfer rate was compared with the theory.In the molecular dynamics simulation, two kinds of intermolecular potential model, C-C and SPC/E, were used for the water surface and probability of condensation was statistically obtained. And molecular exchange phenomenon in which the interface molecule was made to evaporate by the incident molecules was verified. The results showed that condensation probability of water molecule was controlled by the translational motion as well as the monatomic molecule. That is, the condensation coefficient is dependent on surface vertical component of translation energy and on the interface temperature, which is expressed accordin … More g to the same equation for the monatomic molecule. In addition, though the molecular exchange phenomenon existed, it was confirmed that the frequency was little and that the condensation coefficient greatly does not lower from 1.Next, the condensation coefficient based on the transition state theory was examined from the viewpoint of three-dimensional structure of the interface. It was shown that the transition state of condensation process existed in the interface region and that the condensation coefficient can be expressed with free volume ratio of activated complex to the gaseous molecule and with the activation energy. Then, it was checked with the molecular dynamics analysis, and the formation of the condensation coefficient was done from the relation with the interface structure.Finally, non-equilibrium evaporation experiment using the small space was carried out, and the mass transfer rate was measured from the pressure change of vapor phase. The experimental value of condensation coefficient of water resulted in a small value compared to the calculation. Though the existence of the non-condensable gas is considered in the reason, the details is a future problem. Less

水是热工领域的重要材料。本研究采用分子动力学方法研究了水分子在汽液界面的凝结和反射特性。在分子动力学模拟中，采用C-C和SPC/E两种分子间势模型对水表面进行模拟，并统计得到凝结几率。验证了入射分子使界面分子蒸发的分子交换现象。结果表明，水分子的凝聚几率既受平移运动的控制，也受单原子分子的控制。也就是说，冷凝系数依赖于表面垂直转换能分量和界面温度，这是根据…表示的对于单原子分子，同一方程的g更大。此外，虽然存在分子交换现象，但证实了分子交换的频率很小，凝聚系数并不比1低很多。其次，从界面三维结构的角度考察了基于过渡态理论的凝聚系数。结果表明，缩合过程的过渡态存在于界面区域，凝聚系数可用活化络合物与气态分子的自由体积比和活化能来表示。然后用分子动力学分析进行了验证，并从与界面结构的关系上分析了冷凝系数的形成。最后，利用小空间进行了非平衡蒸发实验，并从汽相压力的变化测量了传质速率。水的凝结系数实验值与计算值相比偏小。虽然在原因中考虑了不可凝析气体的存在，但细节是未来的问题。较少