The effect of relative humidity on vapor dispersion of liquefied natural gas: A CFD simulation using three phase change models

LNG is stored in cryogenic conditions, where the temperature is under 111K. In case of an accidental leakage into a normal atmosphere, LNG will vaporize and form cold methane gas cloud, namely LNG vapor cloud. In the existing researches, few have studied the effect of the inevitable water vapor phase change on the dilution of LNG vapor cloud under different relative humidity conditions. In this paper, a two-phase multi-species model is used in combination with three common water phase change treatments to simulate the dispersion of LNG vapor cloud and analyze the effect of relative humidity on it. The three approaches to deal with water phase transfer are: the one neglecting water phase change, and the other two considering water phase change by using the Lee model and the Sun model respectively. It is found that the results obtained by the Lee model and the Sun model show a similar response to humidity. In addition, although the density of LNG vapor clouds is usually higher than that of the surrounding air, there is a chance for the ambient air to overweigh the LNG vapor cloud in a hot and rather wet setting (RH>80%) if water phase transfer is considered.