Dispersion of Permeated Hydrogen in Residential Garages and Assessment of Explosion Hazard for Small Leaks

J.-B. Saffersa, D. Makarov and V.V. Molkov

Hydrogen Safety Engineering and Research Centre (HySAFER), University of Ulster, Newtownabbey, BT37 0QB, UK.


This paper studies dispersion of hydrogen permeated from on-board high pressure storage in a typical residential garage discusses the explosion hazard of lean hydrogenair mixtures associated with permeation and small leaks in enclosures. The original modelling approach is applied to simulate dispersion of permeated hydrogen, based on the introduction of a hydrogen mass source term in a very narrow layer around the storage tank surface. Numerical simulations confirmed a result of analytical analysis that the hydrogen distribution in the garage is practically uniform, allowing the application of the perfect mixing equation for assessment of the maximum hydrogen concentration for given natural ventilation. It is argued that the formation of a flammable hydrogen-air mixture as a result of regulated permeation from a hydrogenpowered car in residential garages is impossible. The explosion hazard of small leaks able to form flammable hydrogen-air mixture in sealed, or under-ventilated, enclosures is discussed. An overview of the experimental data of different authors confirmed that combustion of initially quiescent lean hydrogen-air mixture without turbulisers in the range of hydrogen concentrations 4-8% by volume produces practically no pressure load that could affect the integrity of the garage structure. Calculations of explosion venting areas to mitigate deflagration overpressure to a safe level of 10 kPa in the range of hydrogen concentrations 8-10.5% by volume for the garage are presented.

Keywords: Hydrogen, Permeation, Dispersion, Small leak, Lean hydrogen-air mixtures, Explosion pressure, Venting of deflagration.

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