Modeling of Thin-Layer Drying of Apple Slices in a Semi-Industrial Continuous Band Dryer

The drying kinetics of apple slices was investigated in a semi-industrial continuous band dryer. Apple slices with a thickness of 5 mm were dried at temperatures of 50, 60 and 70 degrees C, air velocities of 0.5, 1.0 and 1.5 m/s and chain linear velocity of 1.85E-04, 2.22E-04 and 2.78E-04 m/s. The Weibull model was fitted to the experimental data of moisture ratio against sample position using MATLAB computer program. The low reduced chi-square and RMSE and the high regression coefficients indicated the suitability of the Weibull model for predicting moisture ratio of apple slices during drying in length of continuous band dryer. Correlations of the scale and shape parameter of the Weibull model with the variables of T, U(a) and U(c) were determined. The transport of water during drying was described by Fick's second low and effective diffusivity varied from 9.24E-08 to 3.5E-07 m(2)/s. The energy of activation was described by the Arrhenius equation and varied from 35.37 to 45.51 kJ/mol.