Influence of detailed in-depth radiation modeling on the computational predictions of liquid pool burning rates

Since thermal radiation substantially contributes to the flame heat feedback, a significant impact is anticipated for the in-depth radiation absorption in pool fires. This research focuses on investigating the influence of a detailed in-depth radiation absorption model on the accurate prediction of the flammability characteristics (i.e., ignition time and burning rate) of liquids in using computational fluid dynamics. First, we determined the radiative properties of hydrogenated tetrapropylene (TPH) (i.e., fuel used in the OECD PRISME project) using UV–Vis–NIR and FTIR spectroscopy and derived an expression for the depth-dependent absorption coefficient and average surface reflectivity. Then, a new approach was introduced for the modeling of in-depth radiation absorption. Subsequently, simulations were conducted for three test cases: heptane evaporation, pool fire, and spill fire scenarios involving both heptane and TPH. Results indicated mild effects of in-depth absorption modeling on heptane evaporation, negligible changes in heptane pool fires, and significant alterations in spill fires compared to the predictions with gray calculations. For all the studied cases except heptane pool fire, the ignition times decreased significantly. Sensitivity analysis revealed that the assumed source temperature had negligible influence on the mass loss rate predictions. The importance of the liquid's Nusselt number (Nu_l) calculation varied between the studied scenarios.