Numerical analysis of temperature stratification in a subatmospheric cold helium line

26th International Cryogenic Engineering Conference & International Cryogenic Materials Conference 2016

材料科学;物理学

Fydrych, J.^1 ; Pietrowicz, S.^2

European Spallation Source ERIC, P.O. Box 176, Lund

221 00, Sweden^1

Wroclaw University of Technology, Department of Thermodynamics, Theory of Machines and Thermal Systems, Wyb. Wyspiaskiego 27, Wroclaw

50-370, Poland^2

关键词: Cryogenic system;    Normal operating conditions;    Operation conditions;    Potential temperature;    Stratification phenomenons;    Subatmospheric pressures;    Superconducting cavities;    Temperature stratification;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/171/1/012023/pdf
DOI  :  10.1088/1757-899X/171/1/012023

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

In last decades the technology of superfluid helium has become very advantageous for large-scale scientific facilities dedicated to high-energy physics. Superconducting cavities or magnets are usually immersed in helium baths at a temperature of 1.8 to 2.0 K. This temperature is produced by a JT cycle where the return line works at a subatmospheric pressure of 16 to 31 mbar. The subatmospheric line lengths can reach even several thousand meters. The helium flows in the subatmospheric lines are driven by cold compressors or vacuum pumps. Due to a limited pressure drop requirement the line diameters can exceed even 300 mm. Since the thermal conductivity of the line material is very small and the flow rate at some operation conditions can be much lower than at the normal operating conditions, a thermal stratification in the helium flow can appear together with a significant temperature gradient along the pipe circumference. These phenomena can affect the thermo-hydraulic behaviour of the line as well as the operation of the entire cryogenic system. The paper presents the numerical simulations of cold helium vapour flows in a long straight line. The stratification phenomenon is discussed and the potential temperature gradient in the pipe wall is evaluated.