Fire engulement of LPG tanks: heatup, a predictive model

Abstract A predictive model of the behaviour of horizontal pressurised LPG vessels engulfed by fire is described. Complete fire engulfment is treated with a heat flux distribution that is both variable in the vertical direction and time dependent. Heat flow through the tank walls, convective and radiative exchange to the fluid and heat and mass transfer between the liquid and vapour are incorporated. The liquid and vapour zones are each assumed to be separately well mixed. The operation of different designs of pressure relief valves is simulated. Model validation was against extensive measurements on 0.25, 1 and 5 tonne LPG tanks filled to a range of levels and engulfed in kerosine pool fires. HEATUP successfully predicted pressure relief valve opening times, discharge rates, pressure histories and average liquid and vapour temperatures for the different tank sizes and fill levels. Predicted mean wall temperatures in both liquid and vapour zones also agreed with measurements.