A computational fluid dynamics evaluation of unconfined hydrogen explosions in high pressure applications

Over the last few decades, the demand for hydrogen has significantly grown. Its high-energy content and relatively small environmental effect make it an ideal energy source and chemical feedstock. However, the perceived high risk of hydrogen in the eyes of society is a key challenge that has to be addressed before any future widespread utilization of hydrogen can be achieved. In this study, the consequences of unconfined hydrogen releases are evaluated using a computational fluid dynamics simulation software, FLACS, to determine the potential to explode. In addition, the study includes the analysis of parameters that can promote hydrogen vapor cloud explosion, e.g., initial pressure, time to ignition, and leak height position. The results conclude that high-pressure hydrogen has the potential to build up a large vapor cloud and may explode even without confinement when the leak source is close to the ground. The highest overpressure produced in the simulation was 0.71 barg, which resulted from igniting a hydrogen gas cloud from a 207 bar hydrogen source leaking at 1 m height. The high overpressure suggests that hazard studies for hydrogen leaks near the ground should not assume a free flow jet release. This study also gives a recommended distance from a high-pressure hydrogen processing unit to nearby occupied buildings to use in conjunction with industrial spacing tables for fire hazards. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.