Performance Evaluation of Passive Ventilation for Hydrogen Leakage in the Room

- Effect of Ventilation Position and Flow Rate on Hydrogen Concentration -

Abstract

The quantity of air exhausted, vent installation location, and hydrogen sensor installation location in a Type 3 ventilation system are studied in order to prevent accidental explosions caused by a Grade 2 hydrogen leak in a closed space. The results reveal that even though the hydrogen concentration in exhausted air is 4％ or less of the lower flammable concentration limit of hydrogen, the local hydrogen concentration in a closed space could be higher than 4 ％. The result of a comparison of three ventilation types with different vent locations—same side ventilation, facing ventilation, and roof ventilation— reveal that the average hydrogen concentration in a closed space decrease in the order: roof ventilation, facing ventilation, and same side ventilation. Furthermore, the hydrogen dispersion behavior of each type shows that in a case where the path of the air flow from the leak to the vent is short, resulting in short circulation, it is possible to efficiently restrict the rise of the hydrogen concentration in the closed space. The wall facing the vent is reached by the air flow from the supply vent, so it is thought to be possible that installing a hydrogen sensor at the top of the wall facing the supply vent will permit early detection of a hydrogen leak.