Thermodynamic study on thermal insulation schemes for liquid helium storage tank

The temperature of liquid helium (LHe) is 4.2 K, high-performance thermal insulation schemes such as the variable density (VD) and self-evaporation vapor-cooled shield (VCS) are required for LHe tank. However, the working parameters of the VD and VCS in LHe tank have not been investigated. However, the related researches on liquid hydrogen tank neglected the heat transfer of the tank wall and the gap; The VD configuration may less than the optimal because the maximum number of spacers for each layer was pre-set artificially. Meanwhile, the recovery rate of sensible heat cannot be obtained by the existing model. In this work, these limitations are taken into account to establish the thermodynamic model of composite multilayer insulation (FMLI), VD and VCS, respectively. The results show that the correction coefficient of FMLI model is 0.1875; The layer densities of composite variable density MLI (FVD-MLI) with four segments are 3.31, 6.62, 13.23, and 19.98 layer/cm, with a 9.6% reduction in heat leakage compared to that of FMLI. The optimal position of the VCS in VCS-composited MLI (FMLI + VCS) and VCS-composited variable density MLI (FVD-MLI + VCS) is approximately 30% and 25% near the cold boundary respectively, and 36.2% and 40.7% reduction in heat leakage compared to that of FMLI and FVD-MLI respectively. The VD and VCS promote each other in improving thermal insulation performance, while the VCS plays a greater role than VD.