The effects of low-temperature phenomena on rapid phase transition of liquid hydrogen

The simultaneous rise in hydrogen economy and cryogenic liquefaction techniques for long-distance storage and transportation has incentivized the development of technological solutions based on the liquefied hydrogen. However, detailed models accounting for the peculiar phenomena of this cryogenic system in the case of accidental release, namely cryogenic evaporation rate and para-ortho transformation, are necessary before large-scale commercialization. In this light, this work aims to unravel this gap of knowledge on safety aspects involving liquid hydrogen through a numerical approach. More specifically, the top events that arose from the accidental release of liquid hydrogen in the absence of ignition have been modeled. A proper evaporation sub-model suitable for cryogenic conditions has been selected in accordance with the literature. The quantum mechanics approach was adopted to estimate the thermodynamic properties of the hydrogen configurations accurately. These estimations were compared with data from the literature, showing excellent agreement. The effect of para-ortho transformation was evaluated by implementing the obtained database. Besides, different releasing surfaces and materials were tested, either solid (e.g., concrete) or liquid (i.e., water), resulting in hydrogen release rate ranging from 2.00×10−4 – to 13.90 kg/s). The generated over-pressures were calculated for all the investigated cases and critically compared with numerical data obtained in this work and analytical model retrieved from the current literature. These results indicate that neglecting the para-ortho transformation represents a non-conservative hypothesis. Indeed, peaks potentially producing significant structural damages were observed only in cases where this transformation was considered.