Hydrogen Stratification in Enclosures in Dependence of the Gas Release Momentum

The hydrogen dispersion phenomenon in an enclosure depends on the ratio of the gas buoyancy induced momentum. Random diffusive motions of individual gas particles become dominative when the release momentum is low. Then a uniform hydrogen concentration appears in the enclosure instead of the gas stratification below the ceiling. The paper justifies this hypothesis by demonstrating fullscale experimental results of hydrogen dispersion within a confined space under six different release variations. During the experiments, hydrogen was released into the test room of 60 m3 volume in two methods: through a nozzle and through 21 points evenly distributed on the emission box cover (multipoint release). Each release method was tested with three different hydrogen volume flow rates (3.17·10−3 m3/s, 1.63·10−3 m3/s, 3.34·10−4 m3/s). The tests confirm the increase of hydrogen convective upward flow and its stratification tendency relative to increased volume flow. A tendency of more uniform hydrogen cloud distribution when Mach, Reynolds, and Froud number values decreased was demonstrated. Because the hydrogen dispersion phenomena impact fire and explosive hazards, the presented experimental results could help fire protection systems be in an enclosure designed, allowing their effectiveness optimization.