CFD modeling on natural and forced ventilation during hydrogen leaks in a pressure regulator process of a residential area

Hydrogen fuel cells have been installed in more than 100 facilities and numerous homes in Ulsan hydrogen town in the Republic of Korea. Despite the advantages of hydrogen, accidents can still occur near residential areas. Thus, appropriate risk mitigation plans should be established. In this study, a computational fluid dynamics (CFD) model of natural and forced ventilation is presented as an emergency response to hydrogen leakages in pressure regulator equipment housing. The CFD model is developed and investigated using three vent configurations: UP, CROSS, and UP-DOWN. The simulation results indicate that the UP-DOWN configuration achieves the lowest internal hydrogen concentration out of the three. In addition, the relationship between the total vent size and internal hydrogen concentration is determined. A vent size of 12% of the floor area has the lowest hydrogen concentration. The use of nitrogen for forced ventilation during emergencies is proposed to ensure that the hydrogen concentration of the released gas is less than one-fourth of the lower flammability limit of hydrogen. Compared to natural ventilation, the time required to reach safe conditions is decreased when nitrogen forced ventilation is used.