Thermal performance and comparative analysis of helical and parallel vapor-cooled shields for liquid hydrogen tank insulation system

Efficient cryogenic insulation is essential for liquid hydrogen storage. In this study, a coupled numerical model integrating effective thermal conductivity calculations is developed. It is employed to investigate thermal performance of liquid hydrogen storage insulation systems incorporating helical and parallel vapor-cooled shields (VCS) with multilayer insulation. Parametric analyses are conducted to examine the effects of tube length, diameter, and shield thickness on insulation performance in helical VCS. Results indicate that the influence of tube length is limited, with heat leakage increasing by only 2.2% as helical turns increase from 1 to 5. Rapid thermal equilibration of hydrogen inside the tube causes extended flow paths to enlarge the high-temperature region and intensify radiative heat transfer. Conversely, tube diameter is identified as the dominant structural parameter. Increasing the diameter from 6 mm to 14 mm reduces heat leakage by 35.0%, as the enlarged convective heat transfer area enhances sensible heat recovery. Meanwhile, a thicker shield improves temperature uniformity, decreasing the VCS temperature standard deviation from 0.281 K to 0.071 K. Moreover, parallel VCS exhibits strong sensitivity to tube number and outperforms helical VCS when at least three tubes are employed due to distributed cooling locations, while helical VCS remains advantageous for applications with stricter structural constraints. These findings provide guidance for the design of advanced cryogenic insulation systems.