THERMAL-BEHAVIOR OF A POROUS REFERENCE MA TERIAL UNDER DIFFERENT HEATING ATMOSPHERES

This study presents an analysis of the temperature evolution in a poro us sample. Various situations have been examined: the porous solid is initially dry or water saturated, and the heating fluid is dry air or steam. This analysis showed experimentally the optimal phases of using steam to heat a material. Moreover, as humidity in the solid consider ably modifies the heating kinetics, the study has also been carried ou t on a non-porous solid. The treatment of the temperature curves under an adimensionnal form shows a singular behaviour of those temperature s following the heating fluid nature and its temperature. Equations gi ving temperature versus time have been proposed. They are based an the definition of a time lag and a time constant, both being defined as a function of the single fluid temperature parameter. Finally, in the p articular case of the non-porous solid heated by dry air, with additio nal approximations, it has been possible to check that the experimenta l time constant is very close to a fundamental time constant.