Small-scale experimental study of vaporization flux of liquid nitrogen released on ice
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IChemE. One of the key steps in Liquefied Natural Gas (LNG) source term modeling is the characterization of heat transfer between substrate and cryogenic liquid. The boiling of cryogenic liquid on water exhibits an immiscible liquid-liquid heat transfer phenomenon where heat transfer parameters change rapidly in a short duration of time. The convective boiling of LNG on over water is influenced by different physical properties of the components present in LNG and the hydrodynamic phenomena that are influencing the boiling process. The boiling process starts on a film boiling regime owing to the large temperature difference and may transfer to transition and nucleate boiling regime as the temperature difference between water and cryogenic liquid decreases. A small scale experimental study was conducted using liquid nitrogen to investigate the heat transfer behavior of cryogenic liquids on water. The amounts of cryogenic spilled and initial water temperature were varied to determine their effect on vaporization rates. The vaporization rates were determined directly from the mass loss measured during the experiment. A variation of heat transfer rate was observed with the change of initial water temperature. The heat flux from water to liquid nitrogen was determined from experimental data and the correlation for convective boiling was validated. Liquid nitrogen was found to be predominantly in film boiling regime. Significant ice formation was observed in spills where the initial water temperature was low. Statistical performance measures were employed to test the performance of phenomenological model for predicting heat flux from water to liquid nitrogen. The model predictions were found to be within a factor of two of the observations. The validated heat flux prediction model is to serve as a sub-model for source term modeling of cryogenic liquid spills.
