DSMC analysis of cryogenic hydrogen expansion in near-vacuum condition

Hydrogen must be stored in a cryogenic temperature at high pressure to increase its energy density. Accidental release of cryogenic hydrogen must be studied before storage and handling safety code can be formulated. The present study simulated axisymmetric pin-hole release of hydrogen at 75 K, 50 K, 25 K and 15 K. The background pressure was set at 0.5 Torr with stagnation pressure at 750 Torr. The high-pressure ratio produced an under-expended shock structure which can be observed for all cases. The analysis was performed using the Direct Simulation Monte Carlo (DSMC) method which model the movement and collision of the gas particles. This code has been validated with experimental data of Nitrogen under-expansion at a similar pressure ratio. the result show that an inward dent formed on the Mach disc at very low temperature. This could be related to the recondensation effectof the flow due to rapid temperature decrease inside the barrel shock. At lower temperatures, the streamlines within the flow spread further apart in a radial direction which could enhence mixing with surroundings. The present work can contribute towards a well-informed hydrogen storage safety standard.