Study On ~3He-~4He Mixture Model And Thermophysical Properties

~3He-~4He mixture is a special cryogenic fluid mixture, with its applications covering cryogenic engineering, fundamental physics and space technology, etc. Optimum system design generally requires knowledge of ~3He-~4He mixture properties. For ~3He-~4He, however, though some theoretical work has been performed and many state properties have been individually measured, the corresponding mixture model explicit in Helmholtz energy form and pressure-explicit state equations along the phase-equilibrium boundaries have never been obtained. Further, no rounded thermodynamic diagrams and modern computer programs are available to calculate the thermophysical properties of ~3He-~4He mixture. In order to provide thermophysical property standards for this mixture and to remove the obstacle for the further development of its applications, the present work focuses on the following sessions:1. Extensive literature survey on ~3He-~4He mixture has been performed and the thermodynamic data have been sorted out, which makes the electronic reference bank and electronic data bank much more plentiful and complete. At the same time, abundant tables and figures have been obtained, which provides a direct view of the trend of all kinds of thermophysical properties.2. Based on experimental data and thermodynamics, the freezing pressure surface of ~3He-~4He mixture has been predicted with relatively high accuracy, using Artificial Neural Network theory. A state equation of freezing pressure covering the whole composition range has been develop for the mixture and the accuracy of the equation between 0.4K-5K meets the engineering standard.3. After examining the experimental data and Artificial Neural Network theory, a detailed flexibility analysis has been carried out on the development of Vapor-Liquid Equilibrium Ancillary Equation within the framework of Helmholtz Energy State Equation and specific procedures outlined.4. Following a discussion on peculiar properties of ~3He-~4He mixture and the advantage of mixture model explicit in Helmholtz energy form, a development strategy concerning ~3He-~4He mixture within the framework of Helmholtz Energy State Equation has been put forward and evaluated.5. The first practical ~3He-~4He mixture model explicit in Helmholtz energy form in the world has been developed. The model's accuracy concerning PVT property of the mixture between 8K and 13K is fairly satisfactory when the composition of ~3He is below 50%, and that in the region above 13K can be enhanced to a higher degree. This practical mixture model can facilitate the enhancement of design and theoretical prediction ability of single-stage G-M type Pulse Tube Refrigerator.