Performance Comparison of Hydrogen Dispersion Models in Enclosure Adapted to Forced Ventilation

In confined spaces, hydrogen released with low momentum tends to accumulate in a layer below the ceiling; the concentration in this layer rises and can rapidly enter the flammability range. In this context, ventilation is a key safety equipment to prevent the formation of such flammable volumes. To ensure its well-sizing to each specific industrial context, it is necessary to dispose of reliable engineering models. Currently, the existing engineering models dealing with the buoyancy-driven H2 dispersion in a ventilated enclosure mainly focus on the natural-ventilation phenomenon. However, forced ventilation is in some situations more adapted to the industrial context, as the wind direction and intensity remains constant and under control. Therefore, two existing wind-assisted ventilation models, elaborated by Hunt and Linden [1] and Lowesmith et al. [2], were tested on forced ventilation applications. The main assumption consists in assuming a blowing ventilation system rather than a suction system, as the composition and velocity of the entering air are known. The fresh air enters the down opening and airhydrogen mixture escapes through the upper one. The adapted models are then validated with experimental data, releasing helium rather than hydrogen. Experiments are conducted on a 1-m3 ventilated box, controlling the release and ventilation rates. The agreement between both analytical and experimental results is discussed from the different comparisons performed.