The Insulation Performance Of Complex Insulation Cryogenic Tank And Investigation On The Thermal Response After Loss Of Insulation Vacuum

With development of cryogenic industry, cryogenic medium need tobe stored in the tank with good insulation performance and vacuumconveniently obtain, so complex insulation cryogenic tank arises at themoment. Because removable cryogenic container such as cryogenicliquid tank car will be in wide application, the accident of loss of vacuumwill consequently increase. So, investigation on the thermal response ofcomplex insulation cryogenic tank after loss of insulation vacuum is ofgreat importance. The present study takes synthetic methods includingexperimental measurements, theoretical analyses and numericalsimulations to investigate complex insulation cryogenic tank withcomplete loss of insulation vacuum. The main research contents include:(1) The effects of the different number of multi-layer insulationmaterial and the changed vacuum degree in insulation jacket on theinsulation performance of complex insulation cryogenic tank areexperimentally investigated. The results show that the evaporation rate ofcomplex insulation cryogenic tank is lower than that of high vacuummulti-layer insulation cryogenic tank with10layers multi-layer materialwhen the vacuum degree in jacket changes from10-3to10-1respectively.Under the condition of meeting the insulation performance of cryogenictank, the complex insulation cryogenic tank is preferred mainly becausethis helps to reduce the cost of vacuum pumping.(2) Heat transfer model of complex insulation with changed vacuumdegree in jacket is proposed on the basis of the principle of heat transfer.The temperature distribution and heat flux are calculated with10layersmulti-layer material. The results of this model agree well with theexperimental data. The difference between experimental and calculatedresults is mainly due to the assumption that the multi-layer material and glass fiber cotton fully contact.(3) A heat transfer model is proposed for heat transfer analysis ofcomplex insulation cryogenic tank with loss of insulation vacuum, andcalculation code is programmed. Experiments with two different jacketwidth and volume cryogenic tank are conducted with nitrogen, heliumand ambient air leaking into the jacket to verify the model. The resultsshow that the big difference arises between experimental results andcalculated ones, which is due to the assumption of ambient pressure equalto that in jacket. At the stable stage of loss of vacuum, the model canprecisely predict the temperature distribution in the jacket.(4) The venting rate and heat flux with complex insulation cryogenictank are lower than those with high vacuum multi-layer insulationcryogenic tank in venting experiments. Temperature on the outer wall ofinner tank and multi-layer insulation material with complex insulationcryogenic tank are lower than those with high vacuum multi-layerinsulation cryogenic tank, and the average value of the differencebetween temperature shows that the complex insulation constructure hasthe performance of thermal shock resistance. The time when the pressurereaches the working pressure of safe valve with complex insulation is twotimes as that with high vacuum multi-layer insulation in no-ventingexperiments, and this also shows that the thermal shock resistance ofcomplex insulation is more advantageous to the rescue of vacuum lossaccident.(5) The venting rate, heat flux and temperature distribution ininsulation jacket with the same complex insulation constructure andinitial liquid level are discussed under the condition of different volumeof two cryogenic tanks when non-condensable gas, condensable gas,sublimated gas and mixed gas are introduced into the insulation jackerrespectively. The experimental results show that the heat flux and thetemperature distribution of these two cryogenic tanks are close to eachother. All these indicate that the experimental results can be appliedwidely.(6) Experimental investigation on the no-venting stage of complexinsulation cryogenic tank after loss of insulation vacuum is performed with different number of multi-layer material layer and leaking gas. Theresults show that the no-venting process can be devided into three stages.The time of no-venting of cryogenic tank increases with the increasing ofthe number of multi-layer material layer, and the time with nitrogenleaking into the jacket is longer than that with ambient air leaking into thejacket. The temperature difference arises between the upper, middle andlower point in the whole no-venting experiments, no matter nitrogen orambient air leaking into the jacket.(7) The supercooled liquid is under the interface between liquid andgas during the whole no-venting experiment. Within the area ofsupercooled liquid, the time when each measuring point reaches themaximum degree of supercooling is same. The supercooling degree isbigger with the more distance from the interface between liquid and gas.The time of the arise of the maximum supercooling degree with ambientair leaking into the jacket is shorter than that with nitrogen leaking intothe jacket, and the maximum value of supercooling degree is bigger thanthat with nitrogen leaking into the jacket. The liquid temperaturestratification in the cryogenic tank after loss of vacuum is numericallysimulated using the two-fluid model. The predicted results agree wellwith the experimental data, this can help to understand the liquidstratification and heat transfer after loss of vacuum. The numericalsimulation makes up the singlemess of the experimental condition andprovides a way to investigate the thermal stratification of cryogenic liquidin the complex insulation cryogenic tank after loss of vacuum.