Thermodynamic modeling of drying of a single body at constant environmental conditions

Modeling of drying process is usually carried out by using the heat and mass transfer equations for prediction of moisture variations of drying material during drying. In this paper, convective air drying of a single body has been modeled using a thermodynamic approach. The proposed model was validated by the experimental data obtained from drying of small spherical potatoes and green tea leaves in a pilot scale dryer. Drying samples were dried at temperatures between 35 and 60°C. The proposed model predicts the temperature and moisture variations and the entropy generation and exergy in the drying sample. The results showed that the air velocity didn’t have a pronounced effect on the drying rate. The surface temperature of the drying material increased rapidly at first, and then reached slowly to the drying air temperature. Also the entropy generation increased at the early stages of drying and then decreased at the end of the drying. Exergy and energy increased during the drying. Comparison of the predictions of the proposed model with the experimental data showed the validity of the proposed model. The average relative error between the predictions of the proposed model and the experimental data (MRE) for humidity and temperature were between, 3.9 and 3.1% for green tea and between 3 and 3.9% for potato samples, respectively.