MATHEMATICAL MODELLING OF THIN LAYER DRYING OF PEAR

In this study, thin-layer drying of pear slices as a function of drying conditions was examined. The experimental data sets of thin-layer drying kinetics at five drying air temperatures (30, 40, 50, 60 and 70 degrees C) and three drying air velocities (1, 1.5 and 2 m s(-1)) were obtained from an experimental setup designed to emulate industrial convective dryer conditions. Five well-known thin-layer drying models from scientific literature were used to approximate the experimental data in terms of moisture ratio. The best model was evaluated numerically. For each model and data set, the statistical performance index (phi) and chi-squared (chi(2)) value were calculated and models were ranked afterwards. The performed statistical analysis showed that the model of Midilli gave the best statistical results. Since the effect of drying air temperature and drying air velocity on the empirical parameters was not included in the basic Midilli model, a generalized form of this model was developed. With this model, the drying kinetic data of pear slices can be approximated with high accuracy. The effective moisture diffusivity was determined by using Fick's second law. The obtained values of the effective moisture diffusivity (D-eff) during drying ranged between 6.49x10(9) and 3.29x10(8) m(2) s(-1), while the values of activation energy (E-0) varied between 28.15 and 30.51 kJ mol(-1).