多屏绝热金属液氦杜瓦的规范化设计方法研究

本文以大口径多屏绝热金属液氦实验杜瓦为研究对象,对之进行了热分析,导出了颈管温度场分布的微分方程。利用数值方法解出了不同蒸发速率下对应的颈管温度场分布,并讨论了多屏屏位的确定方法,在瓶塞与杜瓦材料、结构及尺寸一定的条件下,采用经验式及一些假设,我们求出了理论最小屏数及对应屏位和实际最小屏数及对应屏位,由此计算结果分析了影响多屏绝热绝热性能的主要因素。对瓶塞长度的优化设计我们也进行了讨论。另外文中示出了由最小二乘法获得的一些金属材料热导率及辐射率随温度变化的关系式和氦蒸汽定压比热随温度变化的关系式,这些关系式对杜瓦的规范化设计是必不可少的。采用本文所提供的计算方法可进行多屏绝热金属液氦杜瓦的规范化设计。

A Sutdy of Standard Design Method of Multi-shielded Insulation Metallic Liquid Helium Dewar

Wide-neck multi-shielded heat insulation metallic liquid helium dewar is studiedwith heat analysis given.The differential equation of the temperture distributionof a beck tube is deduced. Using the numerical method,the temperature distribution'ssolutions for different evaporation rates are obtained.The method to determinethe position of the shields is discussed.Under the condition of a given plug of theneck tube and the materials,structures and sizes of the dewar,using empiricalequations and some suppositions as well as.the ideal and practical optimized numberof shields and their positions have also-been obtained respectively.Based on thecalculated results,the important factors are discussed which influence the insulationproperty of multi-shielded heat insulation.The optimization of the plug length hasalso been discussed.In addition,the equations of heat conduetivities and emissivitiesvs.the temperature of some metals are given,and so are equations of the specific heatat constant pressure of helium vapor vs.temperature.These equations attained bythe least squares fitting method are used for standard design.With the designcalculation method supplied by this article,multi-shielded insulation dewars canbe designed satisfactorily.