Heat transfer in a liquid helium cooled vacuum tube following sudden vacuum loss

[摘要] Condensation of nitrogen gas rapidly flowing into a liquid helium (LHe) cooled vacuum tube is studied. This study aims to examine the heat transfer in geometries such as the superconducting RF cavity string of a particle accelerator following a sudden loss of vacuum to atmosphere. In a simplified experiment, the flow is generated by quickly venting a large reservoir of nitrogen gas to a straight long vacuum tube immersed in LHe. Normal LHe (LHe I) and superfluid He II are used in separate experiments. The rate of condensation heat transfer is determined from the temperature of the tube measured at several locations along the gas flow. Instantaneous heat deposition rates in excess of 200 kW/m2 result from condensation of the flowing gas. The gas flow is then arrested in its path to pressurize the tube to atmosphere and estimate the heat transfer rate to LHe. A steady LHe I heat load of ≈25 kW/m2 is obtained in this scenario. Observations from the He II experiment are briefly discussed. An upper bound for the LHe I heat load is derived based on the thermodynamics of phase change of nitrogen.

[发布机构] Mechanical Engineering Department, FAMU-FSU College of Engineering, Tallahassee; FL; 32310, United States^1;National High Magnetic Field Laboratory, Tallahassee, FL; 32310, United States^2

[效力级别] 物理学 [学科分类] 材料科学（综合）

[关键词] Flowing gas;Heat transfer rate;Liquid helium;Nitrogen gas;Phase Change;Rate of condensations;Superconducting RF cavity;Vacuum loss