Modeling Some Drying Characteristics of High Moisture Potato Slices in Fixed, Semi Fluidized and Fluidized Bed Conditions

Drying properties of high moisture potato slices with initial moisture content of about ۴.۰۶ (db) under thin layer fixed, semi fluidized and fluidized bed conditions were studied. Drying air temperatures of ۴۰, ۵۰, ۶۰ and ۷۰°C were applied in experiments using a laboratory fluidized bed convective dryer. In order to predict the drying behavior of potato slices, seven thin layer drying models were applied from where finally Midilli et al. model was selected as the suitable one, based on comparative indices. Effective moisture diffusivity of the potato slices varied between ۴.۲۹×۱۰-۹ and ۱۵.۷۰×۱۰-۹ m۲ s-۱ for fixed and fluidized bed conditions, respectively. Moisture diffusivity values of the slices were increased as the drying air temperature levels increased. Activation energy values varied between ۱۵.۸۸ and ۲۴.۹۵ kJ mol-۱. Minimum and maximum values of activation energy were obtained at minimum fluidized and fixed bed conditions, respectively. Consumption of specific energy for thin layer drying of high moisture potato slices was obtained between ۰.۴۵×۱۰۵ and ۱.۶۴×۱۰۵ (kJ kg-۱). Increase in the drying air temperature in each bed condition caused increase in energy consumption. The maximum value of energy consumption was obtained at fluidized bed conditions.

Keywords:

Drying , Semi fluidized bed , Potato slices , Midilli et al. model , Diffusivity