Liquefied gas over water : an experimental approach at medium scale to assess gas/water interactions and vapor dispersion

Abstract : This medium-scale experiment allowed validating a measuring setup that permits to assess the behaviour of spilled hazardous liquid/liquefied gases over water. Only the spills of liquefied gas hâve been discussed. It appears that most of the gas vaporization occurs below the water line in the mixing cône produced when the jet pénétrâtes vertically into the water. The température of the emitted vapors at the water surface could be estimated and is shown to be significantly différent from the boiling point in some cases. Thus the dispersing cloud may be less cold and less dense than it would be expected for a cloud vaporizing from a still pool spreading at water surface. The physical process observed in our experiment is not taken into account by common conséquence models, which usually considerthat liquefied gas form a boiling pool at water surface. We thus expect that thèse conséquence models used for safety studies would give conservative results when mixing under water is important, since it can be expected that a lighter cloud would lead to shorter safety distances. Anyway, it is clear from the atmospheric measurements that the cloud is very dense close to the source, even though the ambient flow (turbulence and mean wind velocity) has not shown to be disturbed by the présence of the cold cloud of nitrogen - used as a substitute to LNG in the experiments - at this scale. Otherwise it was verified that the visible part of a cloud and its flammable part do not usually match, as the size of the visible cloud strongly dépends on cloud and air températures and relative humidity. Globally, thèse experiments suggest that release conditions - over water, under water, impinging water surface,...- strongly détermine the actual hazardous areas. Thèse trials can be seen as a first expérimental step towards large-scale experiments of liquefied gas releases at sea needed to assess the behaviour of large hazardous dense clouds over water and to validate accidentai dispersion models.
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  • INERIS : EN-2010-119

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Thibauld Penelon, Didier Jamois, Christophe Proust. Liquefied gas over water : an experimental approach at medium scale to assess gas/water interactions and vapor dispersion. 13. International Symposium on Loss Prevention and Safety Promotion in the Process Industry, Jun 2010, Bruges, Belgium. pp.203-210. ⟨ineris-00973571⟩

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