A Dynamic Heat Transfer Model to Predict the Thermal Response of a Tank Exposed to a Pool Fire

Large scale storage of bulk flammable fuels is necessary for distribution of fuel and also provides an opportunity to take advantage of and minimize market risk due to price fluctuations. Due to the inherent flammable properties of fuels, process safety is a key factor in the design of large scale fuel storages, in terms of instrumentation, detail design, emergency preparedness and site layout. In this paper we will describe a method to calculate important input data for the site layout, fire cooling water requirements and the time one can expect will elapse until a fire spreads from one tank to another. To achieve this, a model to calculate emitted radiation from a fire, and the dynamic response and effect on exposed targets is derived. Much data and models, in terms of emitted radiation, is available on traditional fossil fuels, less is available for ethanol and other renewable biofuels. In this paper reviewed experimental data of both fossil fuels and recent data of biofuels is used to fit a radiation model that takes into account type of fuel and size of pool fire to calculate emitted radiation. When it comes to determine the tar gets received radiation, several view factor models are available in the literature. In this paper a modified view factor model is derived to enable calculation of the effect of both wind speed and site topography. Finally a first principle heat transfer model is derived to calculate the thermal response on affected nearby storage tanks in the vicinity of a pool fire. This model takes the following heat transfer mechanisms into account: received radiation, cooling by convection, cooling by radiation on the inside of the tank and cooling by radiation on the outside of the tank. Finally, the model is compared to reviewed experimental data and similar models to evaluate the accuracy in terms of response times for fire spread and radiation levels.