Knowledge of desorption kinetics is essential to predict the behavior of the material during the drying process and to design dryer equipment .The main objective of this study is to obtain the effective diffusivity coefficient and activation energy of shelled pistachio. another goal is to find drying kinetics of shelled pistachio in fluidized bed dryer and ,for this, thin-layer characteristics of shelled pistachios were determined experimentally as a function of temperature and air velocity .Accordingly, 6 mathematical models (Two term model, Exponential model, Logarithmic model, Page model, Modified page model and Henderson & Pabis model) for describing the thin-layer drying behavior of shelled pistachios were investigated. Tests were conducted using four air temperature (25,30,45 and 60 C) ,and three air velocities (6, 8 & 10m/s).Out of the 6 models considered ,the two term model were considered to be the most suitable for describing the drying behavior of the shelled pistachios .Also, for high air temperature and velocity, Henderson-Pabis model proved good suitable .Results showed that air velocity and operating temperature enhanced the kinetics of drying of shelled pistachio and the drying air temperature had a great effect on the drying kinetics. By using of Fick’s second Law the effective diffusivity coefficient and activation energy of pistachio was determined.

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