The Research Of ~3He-~4He Dilution Refrigeration System Heat And Mass Transfer Simulation And Optimization Of Strong Pulsed Magnet

Pulsed High Magnetic Field Device is important to science research under extreme conditions. Dilution refrigeration system is an important part of its cryogenic system. Stable, adequate cooling power and suitable ultra-low temperature environment for scientific experiments can be provided through the optimization of system parameters.According to the actual situation of experimental device, Casing heat exchanger is selected as the suitable form of heat exchangers. By improving the form of heat exchanger, the exchange of heat is strengthened. The materials property is collected before simulation, least squares fitting is selected as the appropriate numerical method, and then the expression of property parameters is educed by programmed calculation. The heat transfer process simulation model is established, the wall temperature and heat transfer coefficient are amended on basis of the fluid-coupling model-Coupled, and the state equations, boundary conditions, physical parameters and math model are combined calculating by UDF programmer. Meanwhile the settings and operations in FLUENT are discussed in detail. The simulation results are compared with the theoretical values, the changing trends is consistent with the theory, the simulation models and results are correct.The performance of casing heat exchanger is simulated and analyzed by FLUENT. First, different heat exchanger length L (0.8m, 1m, 1.2m, 1.4m), different 3He inlet velocity V (0.001m / s, 0.002m / s, 0.003m / s, 0.004m / s), different heat exchanger diameter D (0.3mm, 0.5mm, 0.7mm, 1.0mm) are calculated , and the impacts of these parameters on the area-weighted-average temperature are analyzed. In addition, under the combined situations of the same mass flow, different cycle velocity of 3He V and heat exchanger diameter, the outlet area-weighted-average temperature is calculated, and the changing trend of temperature is found out. Then the impacts of L, V, D parameters on area-weighted-average temperature as well as interaction impacts of these parameters are analyzed.Furthermore, in accordance with the gas-liquid equilibrium and two-phase separation principle, combining with the characteristics of super-fluid helium separation and the needs of Pulsed High Magnetic Field Device with dilution refrigeration system, phase separator of dilution refrigeration system is theoretical analyzed and optimization measures is proposed. And a proposal of structural optimization is given.