Mechanical Effects in Saturated Capillary-Porous Materials during Convective and Microwave Drying

Abstract

The differences are analyzed in distribution and time evolution of the temperature, moisture content, and drying-induced stresses generated by convective and microwave drying. The theoretical analysis of the drying induced stresses and the deformations of dried materials is based on the elastic and viscoelastic constitutive models. The theoretical predictions are confronted with the experimental data obtained by the acoustic emission (AE) method, which enable monitoring on line the development of the drying induced stresses. The system of double coupled differential equations of the thermomechanical drying model is solved numerically using the finite element (FEM) and the finite difference (FDM) methods. A cylindrical sample made of kaolin was chosen to compare experimental data with the model solution. Essential differences were identified in the analyzed items for convective and microwave drying as well as a significant difference in stress distribution was noted for elastic and viscoelastic constitutive models.

Keywords:

• Acoustic emission
• Deformation
• Elastic and viscoelastic models
• Kaolin
• Moisture content
• Stress
• Temperature distribution

Acknowledgment

This work was carried out as a part of research project No 7 T09C 035 21 sponsored by the Polish State Committee for Scientific Research.