Abstract
The increasing use of hydrogen in the energy transition introduces safety challenges, particularly in indoor environments where accidental releases may lead to hazardous accumulations and explosion risks. Due to its low density, high diffusivity, and wide flammability range, hydrogen can rapidly form flammable mixtures, even for relatively small leaks. Accurate prediction of this behaviour is essential for quantitative risk assessment and safe system design. This work presents an indoor dispersion and overpressure model for gaseous releases, implemented in the consequence modelling software EFFECTS.
The model predicts gas accumulation, transport, and explosion effects under both mechanical and natural ventilation conditions and is applicable to hydrogen as well as other gases. Buoyancy-driven behaviour is captured using multiple approaches: ideal mixing for high release rates or neutral gases, a two-layer model for buoyant gases, and an inverse two-layer model for heavier-than-air gases. Additional sub-models account for jet release behaviour, ventilation effects, temperature, and overpressure following ignition. Validation against experimental data and CFD studies shows good agreement for concentration build-up, steady-state values, and overpressure. Minor deviations at low concentrations and high ventilation rates are attributed to the simplified layer representation. Sensitivity analysis demonstrates that ventilation configuration and buoyancy effects strongly influence concentration levels and flammable cloud formation. The model provides an efficient and reliable tool for indoor consequence analysis and can be coupled with outdoor dispersion models for integrated risk assessment.
