Numerical analysis of free convection in cold helium vapor flows in a long sloped pipe

[摘要] The cryogenic systems of large scientific facilities using superfluid helium technologies include a cold helium circuit composed of a subcooled liquid helium supply line and a low-pressure return line. Due to long distances between the cryogenic plant and cryogenic users the line lengths can reach hundreds or even thousands of meters. Usually the low-pressure return line is a large size pipe, which inner diameter can exceed 300 mm. In some cases the accelerators and also the cold helium circuit lines are sloped. In some transient modes there is a risk of a counter flow in the low-pressure return line. This counter flow phenomenon can be driven mainly by free convection and it can disturb the cool down dynamics or affect the performance characteristic of some cryogenic devices, which are sensitive to cool down rates. This paper presents a numerical analysis of free convection in cold helium vapor flows in a long straight and sloped line. The methodology of numerical modeling of the thermo-hydraulic phenomena is described in detail. The results of the numerical simulations performed for various pipe lengths, slopes and mass flow rates are compiled and discussed.

[发布机构] European Spallation Source ERIC, P.O. Box 176, Lund; 22 100, Sweden^1;Wroclaw University of Science and Technology, Department of Thermodynamics, Theory of Machines and Thermal Systems, Wyb. Wyspiaskiego 27, Wroclaw; 50-370, Poland^2

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] Cool-down rate;Cryogenic system;Inner diameters;Mass flow rate;Performance characteristics;Subcooled liquid;Thermo-hydraulic;Transient modes