HYDROGEN CLOUD FORMATION SIMULATION

M. Reza Kameshki*, M. Paraschivoiu§

Concordia University

Montréal, Québec, H3G 1M8, Canada

SESSION: 1.1 Hydrogen release, mixing and distribution

Hydrogenundoubtedly will be one of the, if not the, most important energy carriers in the future. One the major obstacles in hydrogen development as an energy source is the lack of codes and standards in order to assure the safety while using hydrogenin a daily life. Among these standards to be set up, is the determination of clearance distances in case of accidental discharge of hydrogen. The objective of this research is to use Computational Fluid Dynamics (CFD) tools to investigate the dispersion of hydrogen into a room after releasing from a high pressure vessel. This tool can be used to investigate different scenarios.

The analysis consists of two steps, determination of the flow field and solution of hydrogen concentration field. An in-house unsteady flowsolver is extended to solve an extra transport equation for hydrogen species conservation. The code applies an implicit algorithm to 3D compressible Navier-Stokes equations on unstructured tetrahedral grids. The numerical scheme is based on a second-order (in time and space) mixed finite volume-finite element discretization with Roe’s approximate Reimann solver for flux calculations. In order to resolve the turbulent structure of flow field the Spalart-Allmaras single-equation model is used.

After determining the flow field, the mass transport equation for the hydrogen concentration component of the fluid mixture is solved. The mixture of hydrogen and air is assumed to be non-reactive.In order to consider the turbulent diffusion, the laminar diffusion coefficient at each time step is updated according to the turbulent viscosity. Due to high ratio (100 to 800) of the hydrogen pressure at inlet to the room pressure the gradients of the flow variables becomes so sharp, hence in order to capture these gradients, a very fine mesh has to be used in that region. This along with the fact that we need to determine the hydrogen concentration field over the entire room space lead to a large number of nodes which can only be run on parallel machines. Therefore the parallel version of the code is used.

In order to validate the solver, results for hydrogen concentration are compared against the experimental data obtained by J. Chaineaux†. In that experiment hydrogen concentration is measured along the axis of the orifice from which hydrogen is being released. The diameter of the circular orifice is 0.5mm and the initial pressure inside the hydrogen vessel is 400 bars.

* Graduate student, Department of Mechanical and Industrial Engineering, ConcordiaUniversity.

§ Associate professor, Department of Mechanical and Industrial Engineering, ConcordiaUniversity.

† J. Chaineaux, Leak of hydrogen from a pressurized vessel, INERIS.