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

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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