Numerical study of hydrogen leakage, dispersion, and ventilation mitigation in confined car parks

Hydrogen, with its exceptionally high gravimetric energy density and near-zero direct emissions, is widely regarded as an attractive alternative fuel for future transportation systems. However, its use in vehicles introduces safety risks, as hydrogen leakage can potentially lead to fire or explosion. Although hydrogen safety is a critical concern, most hydrogen studies have concentrated on production, storage and conversion technology with comparatively little attention given to the hydrogen leakage and dispersion in a large, complex confined space such as underground car park. This knowledge gap may hinder effective hazard management and increase the accident likelihood. To address this issue, the present study investigates hydrogen dispersion and ventilation mitigation strategies in a confined car park using computational fluid dynamics (CFD) simulations. The model was developed based on industrial standards in China, with a representative vehicle positioned at the center of the car park. Validation against experimental data showed good agreement, confirming the accuracy and reliability of the model. Several ventilation configurations were then systematically evaluated, including variations in blowing and suction. Results indicate that hydrogen tends to accumulate beneath the vehicle, along adjacent walls, and near the ceiling. Among the tested strategies, the most effective configuration involved offsetting supply grilles between two parking slots and delivering air at a 55° angle. This arrangement consistently maintained hydrogen concentrations below safety thresholds, even under varying vehicle positions and leakage orientations. The findings provide actionable insights into ventilation design for confined car parks, contributing to safer integration of hydrogen fuel cell vehicles into urban infrastructure. • Numerical study of hydrogen leakage in confined car parks. • Offset grille at 55° keeps concentrations below safety limits. • Ventilation design insights for safe hydrogen vehicle integration.