Prediction of hazardous area for a hydrogen release

Above a hydrogen concentration of more than 4 volume percent (the so-called lower flammability limit or LFL), the hydrogen-air mixture can be ignited and is therefore a potential risk.
For safety reasons a hazardous area is usually defined as the region with volume percentages above 25% of the LFL. Computational Fluid Dynamics is a great tool to determine the hazardous area for each specific application and release characteristics.

At Flux Engineering we simulated a hydrogen bubble released to the environment through a simple vent into quiescent air. The new modular solver ‘multicomponentFluid’ from OpenFOAM 11 is used to simulate the flow of a compressible gas consisting of two components. The effects of turbulence are modeled by a two-equation eddy-viscosity model (SST) in combination with a given turbulence Schmidt number of 0.7.
Gas enters the vent (D=0.11 m) with constant velocity of 5 m/s at a temperature of 40 C. Only during the first 0.2 seconds the released gas consists of pure hydrogen, in the remainder it is pure air. The environmental temperature is 20 C.

The left side of the movie (slowed-down by a factor 4) shows iso-contours of the hydrogen volume fraction, with the LFL in orange. The LFL of 4 vol% reaches a height of 2.7 m above the vent outlet before dissipating in time.
The right side shows the 25% LFL-contour of the temporal maximum Hydrogen volume fraction, which indicates the extent of the hazardous region for this particular case.

If you are interested in the benefits that CFD modeling can offer for your hazardous area classification, feel free to contact us!