Sustained Hydrogen Leak Concentration in Enclosure with One Vent

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An analytical model for a steady-state hydrogen concentration during a sustained leak in a passively ventilated enclosure with one rectangular vent is described. An equation for hydrogen concentration in vented enclosure as a function of a leak volumetric flow rate is derived in the assumption of perfect mixing. The predictions by this equation are compared against the experimental data on helium release in 0.97 m3 volume enclosure and predictions by currently used equation based on the assumptions of natural ventilation of air in buildings. It is underlined that equations derived for natural air ventilation in buildings, which are often built on the equality of volumetric flow rate in and out of the enclosure through a single vent, are not applicable to the design of passive ventilation systems intended to tackle unscheduled hydrogen releases. The difference in concentration predicted by the former natural ventilation equation and the equation for passive ventilation derived here can be as large as ±2 times that has serious safety implications. The developed model predicted the maximum concentrations of helium measured in experiments fairly good in the whole range of test conditions. It can be recommended as a conservative engineering tool for hydrogen safety engineering even for scenarios with non-uniform hydrogen distribution in enclosure with one vent. Besides, an equation for a mass flow rate limit that leads to 100% of hydrogen concentration in a vented enclosure is presented and discussed.
Original languageEnglish
Title of host publicationUnknown Host Publication
PublisherUniversity of Maryland
Number of pages8
Publication statusPublished (in print/issue) - 10 May 2013
EventSeventh International Seminar on Fire & Explosion Hazards (ISFEH7) - Providence, RI, USA
Duration: 10 May 2013 → …


ConferenceSeventh International Seminar on Fire & Explosion Hazards (ISFEH7)
Period10/05/13 → …


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