This report summarises the ‘rainout’ experiments undertaken by HSE, which was an experimental investigation into the release characteristics and dispersion of elevated spills of LH 2 , including the propensity for rainout to form. A series of 25 LH 2 releases from a tanker delivery hose at elevated positions were carried out through 6 mm, 12 mm and 25.4 mm nozzles with an indicated tanker pressure of 1 or 5 barg. The dispersion from these releases was measured using hydrogen concentration and temperature measurements. Other attributes such as pressure, mass flow rate and temperature were measured in the pipework to provide an understanding of the release characteristics. The experiments were carried out at the LH 2 release facility, which was located on a 32 m diameter concrete pad at the Frith Valley site at the HSE Science and Research Centre in Buxton. While no evidence of rainout was found during these releases, evidence of rainout immediately after a release was observed. Further to this, condensed components of air formed around the release point and on impingements. Pools were only formed with low, vertically downward releases. These pools potentially comprised of LH 2 , condensed components of air, or a mixture of the two. It is possible that with different initial conditions or obstruction geometries, rainout and pool formation could still occur. The phase of hydrogen at the release point was indicated by the pipework measurements. For the majority of the trials a two-phase flow developed within the release pipework. This has been attributed predominantly to the heat transfer into the fluid in the final 3 m of pipework, which contained the instrumentation and therefore was not vacuum insulated. The mass flow rate for each source configuration was measured and is reported including the methodology. The development and dispersion of the gaseous H 2 cloud that forms from a release of LH 2 was captured by the instrumentation and video footage. The jet is typically momentum dominated for the initial section, which ranges between 1.5 m and 6 m depending on the release pressure and nozzle size, but then becomes extremely dependent on the wind, including transient localised gusts. The video and data output of these experiments will be provided for model validation, which is due to take place in upcoming stages of the PRESLHY project.

exel file consists of data from following sensors, obtained during experiments: • near‐field thermocouples • far‐field thermocouples • pressure sensor • tank Pressure sensor • mass flow sensor • H2 concentration sensors • H2 PPM • O2 depletion • near‐field weather station PCE • far‐field wind sensor • far‐field humidity sensor and videos getted during experiments. Report