Nazar Pour, Farhad (2020) Development of a numerical model for simulation of liquefied natural gas (LNG) pool spread and dispersion. (PhD thesis), Kingston University, .
Abstract
Growth in demand for the Liquefied Natural Gas (LNG) has increased calls for further research and development on LNG production and safer methods for its transportation. An essential part of a safety analysis of LNG production, shipment and regasification is to predict incidents such as sudden release of LNG leading to spread and evaporation thus dispersion of natural gas in an open environment. Two main problems are addressed in this research work. First, due to the multi-physics nature of it, a direct 3D simulation approach is computationally costly as it takes high computational time and sophisticated, as it comes across many physical concepts. Complications mainly occurs within the interfaces. Especially, dealing with a multi specie evaporation pool together with evaporation due to boiling. Therefore, a robust and faster numerical method is needed. Furthermore, most of the available models are either 1D or designed for only circular pools and cannot be applied to complex geometries. This research presents a robust methodology to simulate the LNG release scenario through a multi-region numerical method. The novelty of this method is that it is capable to include the effect of heat transfer between the pool and the water substrate and can potentially simulate both pool and gas dispersion in complex environments such as a liquefaction or regasification plant. The model includes many of important effects such as humidity and various atmospheric conditions that can strongly change the dispersion conditions. Additionally, using numerical techniques such as finite area method for a shallow water equation pool model combined with a finite volume based model for gas dispersion provided reasonably faster model for such a large scale incident. The model can be potentially improved to include other factors such as ocean waves and bathymetry effects in changing the pool shape. Validation studies for spreading, evaporation and dispersion were performed using previous large scale LNG release experiments. Additionally, The spread model was also validated for a liquid hydrogen (LH2) over a confined water basin. To compare gas concentration over the experimental domain, two main comparisons were done by comparing arcwise and pointwise measurements. Results were highly dependent on the quality of measured data, especially reported atmospheric conditions. However, both arcwise and pointwise results were in good agreement with measured data. Especially simulations showed excellent performance in pointwise verifications for some of the trials. Moreover, the model performed numerically unconditionally stable and relatively fast with different large scale incidents.
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