Estimation of an Allowable Hydrogen Permeation Rate From Road Vehicle Compressed Gaseous Hydrogen Storage Systems in Garages; Part 2

The time and space evolution of the distribution of hydrogen in confined settings was investigated computationally and experimentally for permeation from typical compressed gaseous hydrogen storage systems for buses or cars. The work was performed within the framework of the InsHyde internal project of the Hy Safe NoE, funded by EC. The main goal was to examine whether hydrogen is distributed homo geneously within a garage like facility or whether stratified conditions are developed, under certain conditions. The nominal hydrogen flow rate considered was 1.087 NL/min, based on the then current SAE standard for composite hydrogen containers with a non-metallic liner (type 4) at simulated end of life and maximum material temperature in a bus facility with a volum e of 681m 3 . The release was assumed to be directed upwards from a 0.15m diameter hole located at the middle part of the bus cylinders casing. Ventilation rates up to 0.03 ACH were consi dered. Simulated time periods extended up to 20 days. The CFD simulations performed with the ADREA-HF code showed that fully homogeneous conditions exist for low ventilation ra tes, while stratified conditions prevail for higher ventilation rates. Regarding flow structure it was found that the vertical concentration profiles can be considered as the superposition of the concentration at the floor (driven by laminar diffusion) plus a concentration difference between floor and ceiling (driven by buoyancy forces). In all cases considered this conc entration difference was found to be less than 0.5%2 The dispersion experiments were performed at the GARAGE facility, using Helium. Comparison between CFD simulations and experiments showed that the predicted concentrations were in good agreement with the expe rimental data. Finally, simulations were performed using two integral models: the fully homo geneous model and the two-layer model, proposed by Lowesmith et al. (ICHS-2, 2007) and the results were compared both against CFD and the experimental data.