A STUDY OF BOILOVER IN LIQUID POOL FIRES SUPPORTED ON WATER .2. EFFECTS OF IN-DEPTH RADIATION ABSORPTION

This study is the continuation of a previous study (Part I) on boilover of liquid fuels supported on water. Previously we designed a small-scale pool-fire apparatus and tested seventeen different (single and multicomponent) liquid fuels on water. Based on this established data, in this paper we describe a one-dimensional model to predict the time required for the water sublayer to start to boil (TWSB). The model includes the unsteady term in the thermal energy equation, along with conduction and in-depth absorption of radiation terms. To fully implement the model, radiation absorption was measured for toluene and Alberta Sweet crude oil as a function of fuel-layer thickness. The model calculation predicts the formation of inverse temperature profiles in the liquid due to the effect of in-depth absorption. Occurrence of the predicted Rayleigh convection in the fuel layer is confirmed using holographic interferometry, and its effect on TWSB is estimated by comparing the model calculations with the experimental results. It is found that a significant amount of heat is transferred from the upper fuel surface to the fuel-water interface by Rayleigh convection, while the heat loss to the walls is found to be moderate.