E. Meisami-asl - Department of Power and Machinery, College of Agricultural Biosystem Engineering, University of Tehran, Karaj, Islamic Republic of Iran.
S. Rafiee - Department of Power and Machinery, College of Agricultural Biosystem Engineering, University of Tehran, Karaj, Islamic Republic of Iran.
A. Keyhani - Department of Power and Machinery, College of Agricultural Biosystem Engineering, University of Tehran, Karaj, Islamic Republic of Iran.
A. Tabatabaeefar - Department of Power and Machinery, College of Agricultural Biosystem Engineering, University of Tehran, Karaj, Islamic Republic of Iran.

Apple is one of the most important fruits. The thin layer drying kinetics of Apple slice is experimentally investigated in a convective dryer and the mathematical modeling by using thin layer drying models in the literature was performed. Drying characteristics of Apples were determined using heated ambient air at temperatures from 40 to 80 °C and velocities 1 m/s and thickness of thin layer 2,4,6 mm. Beside the effects of drying air temperature and velocity, effects of slice thickness on the drying characteristics, drying time and quality of dried product were also determined. Drying curves obtained from the experimental data were fitted to the thin layer drying models. All the models were compared according to three statistical parameters, i.e. root mean square error, chi-square and modeling efficiency. The results have shown that, increasing the drying air temperature and velocity causes shorter drying times. The Midilli et al. model was found to be the best model for describing the drying curves of Apples. The effects of drying air temperature, velocity and thickness on the drying constant and coefficient were also shown.

Modeling Drying, Thin layer drying, Apple slice