Light hydrocarbons and hydrogen can replace high-alkane fuels with the benefit of reduced CO2 emissions. Their liquefaction to a cryogenic state is one of the most suitable solutions for storage and transport. An unexpected release of these fuels might lead to a rapid phase transition (RPT). RPT is a physical explosion well-known for liquefied natural gas (LNG), and may occur when this substance is spilled onto water. The heat provided by the water to the cryogenic fuel might lead to a sudden

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... aporation of the liquid, resulting in an explosion. The generated blast wave has the potential to damage equipment and personnel. The RPT phenomenon can also occur in different types of industrial applications when molten metals accidentally come in contact with water. In these cases, the water is the cold fluid which expands violently. In this study, the RPT phenomenon is investigated for cryogenic fluids (liquefied hydrocarbons, nitrogen and hydrogen) as well as for smelts (molten inorganic salts) and molten metals (aluminum). The contribution has a twofold purpose as it addresses relevant past accidents and lay the foundation for future modelling activities to simulate the cryogenic-pool formation on water, triggering of an RPT event and the RPT explosion consequences. Furthermore, the RPT theories and mechanisms comprehension is critical to qualitatively evaluate the probability for a liquid hydrogen (LH2) RPT. In particular, a comparison between liquid nitrogen (LN2) and LH2 is conducted to understand under which conditions an LH2 RPT might occur. The results of this study are to be validated through the Safe Hydrogen Fuel Handling and Use for Efficient Implementation (SH2IFT) project, in which a series of LH2 spill tests onto water will be conducted.