Determination of Clearance Distances for Venting of Hydrogen Storage

This paper discusses the results of computational fluid dynamics (CFD) modeling of hydrogen releases and dispersion outdoors during venting of hydrogen storage in real environment and geometry of a hydrogen refueling or energy station for a given flow rate and dimensions of vent stack. The PHOENICS CFD software package was used to solve the continuity, momentum and concentration equations with the appropriate boundary conditions, buoyancy model and turbulence models. Also, thermal effects resulting from potential ignition of flammable hydrogen clouds were assessed using TNO "Yellow Book" recommended approaches. The obtained results were then applied to determine appropriate clearance distances for venting of hydrogen storage for contribution to code development and station design considerations. CFD modeling of hydrogen concentrations and TNO-based modeling of thermal effects have proven to be reliable, effective and relatively inexpensive tools to evaluate the effects of hydrogen releases.