Determination and Adaptation of Experimental Drying Curves for Potatoes and Pineapples to Models from the Literature

This study focuses on determining drying kinetics and estimating the products’ diffusion coefficients. A solar dryer equipped with a parabolic trough collector was used. The products were dried in the dryer, and their drying kinetics were monitored. Emphasis was placed on fitting the drying kinetics to empirical and semi-empirical models for potatoes and pineapples during convective drying. During the first phase of the drying process, the moisture content of the agricultural products decreased rapidly, leading to an increase in the drying rate. Moisture content decreased more slowly as drying progressed, resulting in a gradual reduction in the drying rate. Moisture transfer within the products was modelled using Fick's second law, allowing the determination of diffusion coefficients: 6.3456 × 10⁻⁹ m²/s for potato and 2.6647 × 10⁻⁸ m²/s for pineapple. The drying kinetics were adapted to empirical and semi-empirical models using MATLAB software. The evaluation criteria used were the correlation coefficient (R²), the root mean square error ( ), and the root mean square error (RMSE). Among the models tested, the logarithmic model showed the best fit to the experimental potato data, with R² = 0.9978, = 0.00024, and RMSE = 0.01426. For pineapple, this model also shows a good fit with R² = 0.9967, = 0.00043 and RMSE=0.01955. The third-order Gaussian stands out particularly from the other Gaussians with a correlation coefficient R² = 0.9984, the highest for both products.