Determination of the moisture diffusivity coefficient and mathematical modeling of drying

• Calculation methods and programs for diffusion coefficient calculation are created.
• Calculation method represents the solution of Crank and Efremov equation.
• Masonry product shrinkage during drying was entered into the calculation.
• Models, which included a sample shrinkage correction provides acceptable results.
• Results are comparable with other values reported in different studies.

Drying plays an important role in the production of clay tiles. In the present article, drying process is analyzed taking experimental data for several masonry clays obtained from different clay tile manufacturers and published data for different clay slabs. Calculation methods and computer programs designed for the calculation of the effective diffusion coefficient are developed. The first calculation method represents the analytical solution of the Crank equation, while the second one represents the analytical solution of the Efremov equation with boundary conditions in the form of the flux. Unlike other materials, clay tiles exhibit shrinkage during the drying process. For this reason, a shrinkage correction is included in both calculation methods. Four models (A1, A2, B1 and B2) for predicting the drying behavior are obtained as the result of the calculation cited programs. It is shown that the calculated effective diffusion coefficient determined by the designed computer programs, using experimentally obtained and selected published data sets have similar values to those of the same coefficient reported in the literature. Based on the mathematically determined prognostic values of the effective diffusion coefficient, it was concluded that there is more than 90% agreement between the experimentally recorded and the calculated drying curves.