Molecular Dynamics Simulation And Visual Measurement Of Phase Transition Of Deuterium

Deuterium as a nuclear fusion material is very important in the development and utilization of nuclear energy,and deuterium is also used as a civil material in the fields of optical fiber,lubricant performance optimization,special light source,nuclear medicine research,agricultural breeding,pharmaceutical,silicon semiconductor annealing and sintering.In nuclear fusion experiments,high precision deuterium thermal physical parameters are important to the design parameters of ignition target,implosion compression process and the final realization of ignition.At the same time,the phase transition of deuterium is also involved in the nuclear fusion experiment and deuterium preparation.With the development of society,the use of deuterium will be more and more extensive.However,literature research shows that there is still less research on thermal physical properties and phase transition properties of deuterium.Therefore,it is necessary to study the thermal properties and phase transition characteristics of deuterium to obtain more accurate deuterium thermal properties and a deeper understanding of its phase change characteristics.In this paper,the common thermal properties and phase transformation characteristics of deuterium have been studied from two aspects of theory and experiment.The specific research contents and conclusions are as follows:(1)In this paper,a molecular dynamics simulation model of deuterium is built.Then the model is used to simulate the saturated deuterium in the gas-liquid equilibrium.The potential energy parameters in the model,the number of deuterium molecules required and the number of molecular dynamics simulation steps required to achieve the equilibrium of gas-liquid phase are calculated.On the basis of the above research,the gas-liquid interface characteristics of deuterium,the gas liquid density of saturated deuterium,the surface tension and the phase transformation characteristics are simulated and calculated.The simulation results are in good agreement with the literature values,and further research on Deuterium related thermophysical properties can be carried out by using the molecular simulation model.(2)A set of visual experimental devices used to observe the phase transition of low temperature fluid is designed and developed.This device can use a common camera or a high-speed camera to photograph the phase transformation process.The cryogenic refrigerator is used as the cold source and the temperature zone is 10 K to 100 K.Thus the visualization of the liquefaction and solidification process of the common cryogenic fluid can be realized.In this paper,the experimental study of deuterium liquefaction and solidification is carried out.It is found that the solidification process of deuterium is not steady,but is accompanied by a "hole bubble" disturbance.(3)A set of capacitive low temperature fluid density measurement is designed and developed.The experimental device can control the temperature range from 10 K to 100 K,and the measured pressure range is 0 to 0.5MPa.In this paper,the density of deuterium in saturated liquid and under different operating conditions is measured by this experimental device.The deviation of deuterium in saturated liquid and the literature value is within 0.5%,and the deviation of deuterium gas density measurement and literature value is less than 5% under different working conditions.