Experimental and simulation study on transient heat transfer behaviour of multi-layer insulation for cryogenic vessels

The thermal protection systems of cryogenic vessels require adaptability under diverse conditions to maintain thermodynamic stability. Given that the transient heat transfer behaviour of Multi-Layer Insulation (MLI) critically determines the thermodynamic performance and operation safety of cryogenic vessels, an experiment study was conducted at liquid nitrogen temperature on the transient heat transfer of a 90-layer MLI material after liquid nitrogen filling. A modified transient-state simulation model incorporating the unsteady heat transfer of spacers was developed and validated to investigate the transient heat transfer characteristics of the material. The variations of the inter-layer temperatures and heat leakage with time were simulated and compared with the experiment. The study shows that the 30th, 60th layer temperatures and heat leakage all decrease first rapidly and then slowly, where the heat leakage decreases from 0.42 W∙m⁻² to 0.18 W∙m⁻². The maximum deviations of the 30th, 60th layer temperatures and heat leakage between the simulation and experiment are 5.13 %, 4.78 % and 15.15 %, respectively. The heat leakage prediction accuracy of the revised model reaches ± 0.0182 W∙m⁻², which is improved by 23.21 % compared to that of the latest referenced models. The heat leakage is hardly affected by ambient temperature fluctuations, keeping below 0.3 W∙m⁻² for a long period after liquid nitrogen filling. The study reveals the MLI transient heat transfer characteristics during cryogenic vessel precooling operations, and provides important references for optimizing thermal protection system design and enhancing computational accuracy in cryogenic engineering applications.