Fuel Cells and Hydrogen Joint Undertaking (FCH JU); Summary of experiment series E3.5

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
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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.