Experiments on the distribution of concentration due to buoyant gas low flow rate release in an enclosure

Experiments on buoyant gas dispersion in an enclosure have been conducted in a facility of the typical size of a private garage. Helium is used as a model gas for hydrogen. For release flow rate of the order of 0.1 Nl/min to 10 Nl/min, the dispersion is studied in a tightly sealed configuration of the enclosure and for two vertical positions of a vent, near the bottom and near the top. Results are compared to existing simple analytical models. A good accordance is found in the tightly sealed case. With one vent, some significant differences with models are found for the highest flow rates due to a vertical stratification. However a good accordance is found in the limit of very low flow rates even for the simplest model based on a ventilation flow rate independent of the interior mixture density. The main properties of the equivalent flammable atmosphere formed with the vent are presented.