Performance analysis of vapor-cooled shield insulation integrated with para-ortho hydrogen conversion for liquid hydrogen tanks

Abstract

A composite thermal insulation system consisting of variable-density multi-layer insulation (VDMLI) and vapor-cooled shields (VCS) integrated with para-ortho hydrogen (P-O) conversion is proposed for long-term storage of liquid hydrogen. High-performance thermal insulation is realized by minimizing the thermal losses via the VDMLI design and fully recovering the cold energy released from the sensible heat and P-O conversion of the vented gas. Effects of different design considerations on the thermal insulation performance are studied. The results show that the maximum reduction of the heat leak with multiple VCSs can reach 79.9% compared to that without VCS. The heat leak with one VCS is reduced by 61.1%, and further reduced by 11.6% after adding catalysts. It is found that the deterioration of the insulation performance has an almost linear relationship with catalytic efficiency. A unified criterion with relative optimization efficiency is finally proposed to evaluate the improvement of the VCS number.