Safety studies on vacuum insulated liquid helium cryostats

[摘要] The loss of insulating vacuum is often considered as a reasonable foreseeable accident for the dimensioning of cryogenic safety relief devices (SRD). The cryogenic safety test facility PICARD was designed at KIT to investigate such events. In the course of first experiments, discharge instabilities of the spring loaded safety relief valve (SRV) occurred, the so-called chattering and pumping effects. These instabilities reduce the relief flow capacity, which leads to impermissible over-pressures in the system. The analysis of the process dynamics showed first indications for a smaller heat flux than the commonly assumed 4W/cm2. This results in an oversized discharge area for the reduced relief flow rate, which corresponds to the lower heat flux. This paper presents further experimental investigations on the venting of the insulating vacuum with atmospheric air under variation of the set pressure (pset) of the SRV. Based on dynamic process analysis, the results are discussed with focus on effective heat fluxes and operating characteristics of the spring-loaded SRV.

[发布机构] Karlsruhe Institute of Technology (KIT), Institute for Technical Physics, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen; 76344, Germany^1;Karlsruhe Institute of Technology, Institute for Thermodynamics and Refrigeration, Kaiserstrasse 12, Karlsruhe; 76131, Germany^2;Paul-Scherrer-Institute (PSI), WMHA/C46, Villigen PSI; 5232, Switzerland^3;European Organization for Nuclear Research (CERN), Geneva 23; CH-1211, Switzerland^4

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] Discharge instabilities;Experimental investigations;Insulating vacuum;Liquid helium;Liquid helium cryostats;Operating characteristics;Process dynamics;Safety relief valve