by William E. Marinsen and Jeffrey D. Marx
Abstract
This paper presents an integrated model for predicting the radiant heat effects of fireballs created by near-instantaneous releases of superheated flammable liquids. Films and videos of fireballs show that a fireball grows quickly in size, rises into the air after some time delay, then dissipates when the available fuel is consumed. Most of the published fireball radiation models ignore this behavior and simply assume the diameter, location, and surface emissive power of the fireball are constant over the full duration of the event. In contrast, the model described in this paper provides a more realistic representation of the true behavior of fireballs by employing equations that account for fireball growth, lift-off, and changing radiative characteristics. Thermodynamic changes that occur during the release of superheated liquids are incorporated into the model, making it suitable for predicting the radiant heat effects of fireballs formed as a result of cold catastrophic failures of pressure vessels, as well as fireballs created by BLEVE incidents. Predictions of the time-varying radiant heat flux incident upon targets located outside the fireball are shown to agree well with results from moderate-scale experiments.