On the Determination of the Crossing-Point Temperatures for Evaluating Reactivity of Solids

Abstract

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 that occurred during the self-heating of solids. By numerically simulating the thermal response of a solid sample placed in a convective thermal environment, the variation in the trend of the enthalpy change term together with the heat generation term in the sample central elementary volume was monitored, which allowed a close observation on the formation of a CPT. It was found that a true CPT is the transition temperature at which the heat transfer from the surroundings to the central neighborhood goes into reverse. The CPT values measured during practical testing may be altered by experimental settings for finding equal temperatures between the sample centre and a reference point, which is more evident at the 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 yielded a theoretical correlation for determining the maximum distance for the reference temperature sensor to be placed in order to perform reliable measurement of a CPT. This correlation is in excellent agreement with the experimental settings for the reference point adopted by various research groups.KEYWORDS: solid, self heating, spontaneous ignition, crossing-point temperature. NOMENCLATURE LISTING