For hydrogen safety studies it is important to study both the dispersion and the resulting explosion of the mixture. A simplified approach in a safety study would frequently assume that the entire tank contents can contribute to an explosion if released. However, actual hydrogen releases seldom follow this approach and a detailed dispersion study may indicate that only a very limited amount of hydrogen will contribute to an explosion if ignited. Below two gas clouds are compared. The upper image shows the resulting worst-case gas cloud predicted by a dispersion simulation, while the lower image shows an unrealistic worst-case cloud assuming that all available hydrogen can form a stoichiometric cloud if released in a tunnel. The explosion pressures obtained if the unrealistic cloud is ignited would be 1-2 orders of magnitude higher than those obtained from an ignition of the upper, worst-case gas cloud predicted from a realistic dispersion calculation.
GexCon has significant experience and has written several articles in recent years within the field of modeling of hydrogen safety. The Hydrogen Research Advisory Council concluded that FLACS was the "only widely used commercial tool for hydrogen explosion" (NFPA-website, page 6 of report). Please contact us for more information about services and software.
Hydrogen is a very reactive gas with significantly higher flame speeds than natural gas. In addition, hydrogen also has a much wider flammability range that needs to be considered when evaluating hazards. However, due to the strong buoyancy effects, hazards associated with the handling of hydrogen may still be within acceptable limits. GexCon can help clients study the combined release, dispersion, ventilation and explosion with our CFD simulation tool FLACS.
