Validation of CFD Modelling of LH2 Spread and Evaporation Against Large-Scale Spill Experiments

Hydrogen is widely recognized as an attractive energy carrier due to its low-level air pollution and its high mass-related energy density. However, its wide flammability range and high burning velocity present a potentially significant hazard. A significant fraction of hydrogen is stored and transported as a cryogenic liquid. Therefore, loss of hydrogen containments may lead to the formation of a pool on the ground. In general, very large spills will give a pool, whereas moderate sized spills may evaporate immediately. Accurate hazard assessments of storage systems require a proper prediction of the liquid hydrogen pool evaporation and spreading. A new pool model handling the spread and the evaporation of liquid spills on different surfaces has recently been developed in the 3D Computational Fluid Dynamics (CFD) tool FLACS [1-4]. As the influence of geometry on the liquid spread is taken into account in the new pool model, realistic industrial scenarios can be investigated. The model has been validated for LNG spills on water with the Burro and Coyote experiments [5,6]. The model has previously been tested for LH2 release in the framework of the EU-sponsored Network of Excellence HySafe where experiments carried out by BAM were modelled. In the large scale BAM experiments [7], 280 kg of liquid hydrogen was spilled in 6 tests adjacent to buildings. In these tests, the pool spreading, the evaporation, and the cloud formation were investigated. Simulations of these tests are found to compare reasonably well with the experimental results. In the present work, the model is extended and the liquid hydrogen spill experiments carried out by NASA are simulated with the new pool model. The large scale NASA experiments [8,9] consisted of 7 releases of liquefied hydrogen at White Sand, New Mexico. The release test 6 is used. During these experiments, cloud concentrations were measured at several distances downwind of the spill point. With the new pool model feature, the FLACS tool is shown to be an efficient and accurate tool for the investigation of complex and realistic accidental release scenarios of cryogenic liquids.