A NUMERICAL DRYING MODEL THAT ACCOUNTS FOR THE COUPLING BETWEEN TRANSFERS AND SOLID MECHANICS. CASE OF HIGHLY DEFORMABLE PRODUCTS

Abstract

Derived from a previous version of TransPore, the numerical model presented in this work has been developed in order to describe the drying of porous media that undergo large deformations due to shrinkage. For such products, the change of geometrical shape has to be taken into account to solve the balance equations. The initial product shape is described using triangular elements. From this classical FE mesh, Control Volumes are built and used to solve heat and mass transfer equations, while the initial FE mesh is used to solve the mechanical problem. Due to large shrinkage values, non-linear problems arise from the large strain field generated during the process. In order to overcome this difficulty, the constitutive law is written on a local intermediate configuration in which rotation is chosen to oppose the rotation appearing in the polar decomposition of the deformation gradient tensor. One typical example is presented for potato. This product has its most part of shrinkage within the domain of free water. Consistently, the sample shape varies significantly although free water remains available at the exchange surface. Paradoxical results can be obtained when simulating low convective drying of this product: a decreasing drying rate flux is exhibited during the first drying period. This paradox, which has also been observed during experiments, is obviously due to the reduction of the exchange surface.

Keywords:

• Control volume
• Drying model
• Finite element
• Large deformation
• Large strains
• Food
• Shrinkage

Acknowledgments