Energy considerations in the spreading of LNG on sea water

The spreading of an accidental spill of Liquefied Natural Gas (LNG) on sea water has been studied for many years and several theoretical models have been proposed and successfully used. Many modeling techniques have been used by researchers for the spreading of LNG. However, most of these neglect the heat transfer aspects related to the spreading, and the effect of temperature dependent properties such as density, thermal conductivity and specific heat of LNG is not included in the analysis. In the present study, this situation is redressed by including the depth-averaged energy equation in a one-dimensional model of the spreading of LNG on sea water. The thermophysical and transport properties of the fluid are made temperature-dependent and heat transfer to the pool from the water below and the flame above are included. The resulting set of coupled one-dimensional mass, radial momentum and energy balance equations are solved numerically using an explicit, second order-accurate finite difference method-based discretization of the governing equations. Results obtained in the present study show that the incorporation of the variable properties gives significantly improved predictions over conventional models. The predicted results are compared with the experimental results of Raj et al [1], and with a conventional, constant-properties model of Fay [2] for the test case #12. Excellent agreement is found between the current model predictions and the experimental data while the conventional model overpredicts the pool diameter for longer times. It is demonstrated that the present approach is inherently capable of distinguishing between the spreading of different LNG mixtures, and can therefore be readily extended to the analysis of the accidental spill of any other hazardous substance. Copyright © 2008 by ASME.