Effect of Wind on Cryogenic Hydrogen Dispersion from Vent Stacks

Liquid hydrogen vent stacks often release hydrogen, for example, due to pressure relief from an underutilized tank boiling off hydrogen or after hydrogen delivery and transfer (trucks often depressurize through the tank vent stack to meet pressure regulations for on-road transport).
A rapid release of cryogenic hydrogen through a vent stack will condense moisture from the entrained air, forming a visible cloud. It is often assumed that the extent of the cold hydrogen is concurrent with the cloud. In this work, a laser-based Raman scattering diagnostic was used to map out the hydrogen location during a series of vent stack release experiments. A description of the diagnostic instrument is given, followed by a comparison of hydrogen signals to the visible cloud for releases through a liquid hydrogen vent stack. A liquid hydrogen pump was used to vary the flowrate of hydrogen through the vent stack and tests were performed under low and high wind conditions as well as low and high humidity conditions. The hydrogen was observed only where the condensed moisture was located, regardless of the humidity level or wind. These measurements are being used to validate models such as those included in Sanda’s HyRAM toolkit and inform safety codes and standards.