Study on the Performance of Variable Density Multilayer Insulation in Liquid Hydrogen Temperature Region

The storage of hydrogen is important for the development of hydrogen energy, especially for the storage of liquid hydrogen, which has been receiving more and more attention recently. In order to study the thermal insulation performance of variable-density multilayer insulation (VDMLI) structures under different working conditions at liquid hydrogen temperatures without incorporating a composite structure, we established a heat transfer model based on a layer-by-layer calculation method. Then, we carried out numerical calculations to analyze the influence of the total number of layers, the thermal boundary temperature, and vacuums on the performance of MLI at liquid hydrogen temperatures. To investigate the optimization of variable-density configurations on the thermal insulation performance of VDMLI and to obtain accurate variable-density configurations, we proposed a variable-density configuration method based on the control variable method and the insertion by region method. The results indicate that the optimal variable-density configuration is the insertion of 4 layers of radiation shields in the low-density region, 15 layers in the medium-density region and 38 layers in the high-density region. Compared with a uniform-density structure, the heat flux is reduced by 8.6%.