The Research Of The Experiment And The Heat Transfer Mechanism On The High-Vacuum-Multilayer-Insulation (Hvmli) Cryogenic Tank After Catastrophic Loss Of Insulating Vacuum

The sudden, catastrophic loss of insulating vacuum (SCLIV) is one of the most extremely severe conditions that may be encountered during the using process of a HVMLI cryogenic tank. When it occurs, heat transfer across the insulation jacket is very complicated and has significant effects on the thermal performance of the tank. Previous studies focused mainly on the security and reliability of SCLIV cryogenic tanks, and their conclusions were poor in universality and had little practical value in the industrial applications. At the same time, most of previous studies were aimed at obtaining macro-scale parameters such as the evaporation rate, heat flux and pressure increase, but focused rarely on the heat-transfer mechanisms. For the purpose of pursuing an in-depth understanding of the heat transfer process across the insulation jacket with SCLIV and its impact on the stored cryogenic liquid, the present study takes synthetic methods including experimental measurements, theoretical analyses and numerical simulations to investigate HVMLI cryogenic tanks with SCLIV. The main research activities include:(1) A heat transfer model is proposed for heat transfer analysis of HVMLI cryogenic tank with SCLIV. Some important parameters affecting heat transfer across the insulation jacket are comprehensively discussed. The results show that the outer wall temperature, the number of insulating layers, the leaking gas and the package density of the insulating layers are key factors affecting heat transfer across insulation jacket after SCLIV. The thermal conductivity of spacer mateials has little effect on the heat transfer process and the height of the tank has no visible effects on it.(2) The effects of the initial liquid level and the insulation layer number on the HVMLI cryogenic tank with SCLIV are experimentally investigated. The results demonstrate that the insulation layer number play an important role in impacting the heat transfer process in the HVMLI cryogenic tank with SCLIV, whereas the initial liquid level rarely affects the heat transfer process. The calculated results using the heat transfer model agree well with the experimental data, which verifies the effectiveness of the model.(3) The effects of different gases, including non-condensable gas, condensable gas, sublimated gas and mixed gas on the HVMLI cryogenic tank with SCLIV are experimentally investigated. The results proved that the heat transfer process is significantly affected by two major factors: one is gas condensation and sublimation make heat flux increase sharply at the initial stage of the SCLIV; the other is the liquid or solid adhering to the inner vessel and insulation materials makes the heat transfer enhanced. The composited thermal conductivityλcom has been proposed for the heat transfer process of insulation jacket with condesable and sublimated gases. According to the experimental results from the insulation jacket with carbon dioxide and oxygen, the correlation ofλcom changing with time and the number of insulating layers has been proposed.(4) The effects of the initial liquid level and insulation layer number on liquid storage of the HVMLI cryogenic tank with SCLIV are experimentally investigated. The results show that the both factors significantly affect the liquid storage. TheАгафоновИ.М. calculation model has been improved so that it can calculate accurately the pressurization process under high heat flux conditions (180～220W/m2 and 280～320W/m2). The calculated results agree well with the experimental data (the maximum relative error is less than 23%).(5) The liquid flow and temperature stratification in the HVMLI cryogenic tank with SCLIV are numerically simulated using the two-fluid model. The predicted results agree well with the experimental data (the maximum relative error is less than 3%), especially for the instantaneous flow of cryogenic liquid and its temperature stratification was described in detail. The simulated results make up for the lack of experimental techniques and provide a new methods and means to the study of the liquid flow and heat transfer after SCLIV deeply.