Effect of temperature and slice thickness on drying kinetics of hot- air drying of hawthorn slices

In this study,hawthorn slices were dried as thin- layers with thickness of 2 mm and 4 mm in the ranges of50~90 ℃ of drying temperature in a hot- air dryer. The effect of drying hot- air temperature and slice thickness on the drying kinetics was analyzed.Five different dynamic models were fitted nonlinearly by using the drying test data of hawthorn slices and the best suitable model was selected by comparing the values of the correlation coefficient( R²),the reduced chi- square( χ²) and the root mean square error( RMSE).The results showed that drying process of hawthorn slices occurred in the falling rate period,and the moisture transfer was controlled by internal diffusion.The Page model was the best suitable to descript the relationship of hawthorn slices moisture and drying time by hot- air drying.The effective moisture diffusion coefficient( D_eff) and the activation energy( E_a) were also obtained by experiments under different conditions,the values of D_eff was increased with the addition of drying temperature and slices thickness,and Deffvalues changed from 2.69 × 10^-11m²/ s to 16.12 × 10^-11m²/ s within the given temperature range.An Arrhenius relation with Eavalues of 20.43 k J / mol and 26.25 k J / mol for the thickness of2 mm and 4 mm expressed the effect of temperature and sample thickness on the diffusivity.