Modelling the Non-adiabatic Blowdown of Pressurised Cryogenic Hydrogen Storage Tank

This paper describes a model of hydrogen blowdown dynamics for storage tanks needed for hydrogen safety engineering to accurately represent incident scenarios. Heat transfer through a tank wall affects the temperature and pressure dynamics inside the storage vessel, and therefore the characteristics of the resulting hydrogen jet in case of loss of containment. Available non-adiabatic blowdown models are validated only against experiments on hydrogen storages at ambient temperature. Effect of heat transfer for cryo-compressed hydrogen can be more significant due to a larger temperature difference between the stored hydrogen and surrounding atmosphere, especially in case of failure of equipment insulation. Previous work by the authors demonstrated that the heat transfer through a discharge pipe wall can significantly affect the mass flow rate of cryogenic hydrogen releases. To the authors’ knowledge thoroughly validated models of non-adiabatic blowdown dynamics for cryo-compressed hydrogen are currently missing. The present work further develops the non-adiabatic blowdown model at ambient temperature using the under-expanded jet theory developed at Ulster University, to expand it to cryo-compressed hydrogen storages. The non-ideal behaviour of cryo-compressed hydrogen is accounted through the high-accuracy Helmholtz energy formulations. The developed model includes effect of heat transfer at both the tank and discharge pipe wall. The model is thoroughly validated against sixteen tests performed by Pro-Science on blowdown of hydrogen storage tanks with initial pressure 0.5-20 MPa and temperature 80-310 K, through release nozzle of diameter 0.5-4.0 mm. The model well reproduces the experimental pressure and temperature dynamics during the entire blowdown duration.