Modeling Thin Layer Drying Kinetics, Moisture Diffusivity and Activation Energy of Hazelnuts during Microwave-Convective Drying

The effects of microwave-convective drying as an efficient drying method, on drying kinetics of hazelnuts were studied. Drying experiments were conducted at three temperature (40, 50 and 60 degrees C) and microwave power (0, 450 and 900 W) levels. The moisture ratio and the temperature of the hazelnuts were recorded during the drying. The results showed that microwave power had a more dominant effect than drying air temperature. Mathematical modeling was performed in order to predict the moisture changes during drying process. It was concluded that two term and Midilli et al. models were the best models to predict the drying kinetics of hazelnut in different conditions. The effective moisture diffusivities varied from 3.80327x10(-8) to 1.71233x10(-6) m(2)/s and had an increasing polynomial relationship with temperature and microwave power. The activation energy was also between 15.61675 and 41.0053 kJ/ mol with a second-order relationship with microwave power.