Effect of substrate thermal properties on evaporating liquid hydrogen and ammonia spills

Abstract

To decarbonize the energy, transport and industrial sectors, liquid hydrogen and ammonia are likely to be more widely employed. During an accidental release, these cryogens quickly spread and evaporate, producing explosive ($H_2$) or toxic (${\mathrm{NH}}_3$) clouds. Assessing the risks associated with storage and transport therefore requires tools that can simulate these spill processes, accounting for both the spill source, geometry and substrate thermal properties. In this work we have developed a flexible tool that takes the details of the spill, geometry and substrate as input. The parameters include initial spill velocity, ground topography, obstructions, and details regarding the thermal properties of the substrate. The latter includes temperature-dependent thermal properties, porosity and potential freeze out of trapped water. We validate this model against experimental data and apply it to relevant $H_2$ and ${\mathrm{NH}}_3$ spill cases. Evaporation rates were found to vary significantly with substrate characteristics, and this is expected to have a large impact on safety distances.