Analytical Model of Cryogenic Hydrogen Releases

Hydrogen is one of the most promising alternative sources to relieve the energy crisis and environmental pollution. Hydrogen can be stored as cryogenic compressed hydrogen (CcH2) to achieve high volumetric energy densities. Reliable safety codes and standards are needed for hydrogen production, delivery, and storage to promote hydrogen commercialization. Unintended hydrogen releases from cryogenic storage systems are potential accident scenarios that are of great interest for updating safety codes and standards. This study investigated the behavior of CcH2 releases and dispersion. The extremely low-temperature CcH2 jets can cause condensation of the air components, including water vapor, nitrogen and oxygen. An integral model considering the condensation effects was developed to predict the CcH2 jet trajectories and concentration distributions. The thermophysical properties were obtained from the COOLPROP database. The model divides the CcH2 jet into the underexpanded, initial entrainment and heating, flow establishment and established flow zones. The condensation effects on the heat transfer and flow were included in the initial entrainment and heating zones. The empirical coefficients in the integral model were then modified based on measured concentration results. Finally, the analytical model predictions are shown to compare well with measured data to verify the model accuracy. The present study can be used to develop quantitative risk assessment models and update safety codes and standards for cryogenic hydrogen facilities.