CFD modeling of flash evaporation occurring inside a liquid hydrogen pipe leak and its consequences on the conditions at the breach

In the context of energy decarbonization, hydrogen turns out to be an interesting candidate for transport-related issues, and is already used as alternative to fossil fuels for ground vehicles. However, for air transport, this solution has still not been implemented on a large scale because it requires the development of new aircraft and adequate airport infrastructure. The safety conditions that currently exist for aircraft using kerosene must be adapted to the issues posed by the storage and transport of liquid hydrogen. Among them, the risk of a leak in the refueling pipeline needs to be evaluated, as it can impact the working people and the passengers around. The resulting plume that can appear is strongly dependent on the phase change that occurs inside the leak and the mass flow at the breach. The objective of this study is to model the phase change that occurs in a liquid hydrogen pipeline due to a leak using the CEDRE (Calcul d’Écoulements Diphasiques Réactifs pour l’Énergétique) software from ONERA (Office National d’Études et de Recherches Aérospatiales). This study is focused on the influence of different parameters on the mass flow at the leak exit and on the phase change occurring inside the leak, which represents the novelty of the work. Comparisons with similar phenomena with H 2 O as transport fluid are performed due to insufficient experimental data for the studied configurations with H 2 . First the Computational Fluid Dynamics methodology is presented. Then, the different configurations are detailed. Finally, the results obtained from the parametric study are presented to conclude on the effects of pipe mass flow, pressure inside the pipe, leak diameter and hydrogen temperature on the phase change and mass flow in the leak. The phase change inside the leak is strongly impacted by the temperature inside the pipe. The flow is mainly gaseous at the exit for all the studied cases except for the sub-cooled ones: the lower the temperature, the lower the evaporation. The ratio between the simulated and the Bernoulli mass flows, which represents the discharge coefficient, is close to 0.6 for the most sub-cooled cases but decreases to values between 0.3 and 0.4 when the injected liquid H 2 is at thermodynamic equilibrium, no matter the other conditions.