THE USE OF TIME TO IGNITION DATA FOR CHARACTERIZING THE THERMAL INERTIA AND THE MINIMUM (CRITICAL) HEAT-FLUX FOR IGNITION OR PYROLYSIS

The objective of this work is (1) to determine to what extent current methods for interpreting time-to-ignition data accurately represent the heatup of a given material when surface reradiation and convection losses are significant, and (2) to propose modifications in the current procedures for deducing the thermal inertia and the critical heat flux. A numerical solution for the surface temperature histories of thermally thick materials including surface reradiation was obtained by employing a single free parameter Volterra equation and a continuation method numerical algorithm. In addition, excellent approximate solutions by asymptotic methods were developed. These approximate solutions are essential for the reinterpretation of time-to-ignition data. The numerical solutions were compared with detailed surface temperature histories obtained in a new flammability apparatus, while the new equations for interpreting time-to-ignition data were also validated by comparison with the exact solutions and experimental data.