A Model Considering the Flame Volume for Prediction of Thermal Radiation from Pool Fire

Abstract

Thermal radiation is an important parameter to evaluate the hazard of pool fires. In the conventional solid flame model for the radiant heat flux calculation, the burning flame is often assumed to be of a cylinder or a cylinder–cone combined shape whose height and diameter equal the flame height and pool diameter, respectively. Obviously, the conventional model does not take into account the actual flame volume. Thus, this paper presents a revised solid flame model by correcting the flame diameter with the flame height and flame volume. The heat release rate per unit flame volume is approximately 1100 kW/m3 for hydrocarbon pool fires, by which the flame volume can be calculated with the known heat release rate. By theoretical analysis on experimental data in literature, correlations of centerline temperature and flame emissivity are proposed to calculate the flame surface emissive power of heptane pool fires. The obstruction effect of smoke around the burning flame on the thermal radiation is also considered by correcting the transmissivity of thermal radiation in the surrounding medium. Comparisons in prediction between the new and conventional models are conducted against the experimental measurements of 0.3 m, 0.5 m, 0.7 m, 1 m, 6 m heptane pool fires. It is found that the new model with the cylinder–cone combined shape assumption can better predict the thermal radiation from heptane pool fires in both near and far fields.