Fire Safety Science Digital Archive

In this paper, we study the physical basis of the crossing-point temperature (CPT) techniques and seek guidelines for attaining reliable evaluation on the kinetic parameters of the exothermic reactions occurred during self-heating of solids. By numerically simulating thermal response of a solid sample in a convective thermal environment, the variation trend of the enthalpy change term together with the heat generation term in the central elementary volume was monitored, which allowed an close observation on the formation of a CPT. It is found that a true CPT in nature is the transition temperature when the heat transfer from the surroundings to central neighborhood goes to the reverse. The CPT values measured during practical testing may be altered by experimental setting for finding equal temperatures between the sample centre and a reference point, which is more evident at conditions of enlarged sample sizes and elevated oven temperatures. Relaxation on the criterion of the equality between the enthalpy change term and the heat generation term in the central elementary volume yields a theoretical correlation for determining the maximum distance for the reference temperature senor to be placed in order to achieve reliable measurement of CPTs. This correlation is in excellent agreement with the experimental settings for placing the reference point adopted by distinct research groups.