Characterization of the First Falling Rate Period During Drying of a Porous Material

Abstract

This study deals with the evolution of the surface state and its influence on the drying of porous media. Surface temperature and saturation values are obtained using optical metrology. Analysis of the experimental results allows discussion of the apparition of constant drying rate period and to characterize the transition to the falling rate period. A mathematical model is developed to account for these observations and experimental results for some physical properties of a model material. It allows determination of the internal profile of moisture and the penetration of the drying front during the falling rate period.

Keywords:

• Diffusion model
• Evaporation front
• Surface saturation
• Surface temperature
• Porous media
• Brick

Acknowledgments

Experiments were carried out in “Laboratoire d'Etudes Thermiques”, University of Poitiers (France), with the assistance of Dr Jean-Paul Fohr. The author is grateful to Professor A.S. Mujumdar for his careful review of the paper.