A di †usion-based drying model has been used to model the single-layer drying of whole hazelnuts (hull, air-gap and kernel). The drying of whole hazelnut was simulated by means of the numerical solution of FickÏs second law for a composite solid consisting of an air gap which is between two solid bodies. The CrankÈNicholson implicit numerical method has been applied to solve the di †usion equation with variable mass di †usivity for whole hazelnut. The numerical data so obtained has been presented in the form of a series of curves which represent the drying characteristics of a whole hazelnut. Experimental results from whole hazelnuts were correlated with the theoretical results. A correlation describing the di †usivity of the whole hazelnut with moisture content and temperature was established, when the expression of di †usivity for hazelnut was used. Predicting the drying behaviour of the hazelnut for a known value of initial moisture content, equilibrium moisture and equivalent radius, a good agreement was obtaind between the experimental data and prediction. Whole hazelnut diffusivity was determined at 25È45¡C, air velocity 0É2È0É3 ms~1, 60% relative humidity of air, using the theoretical curves that best Ðt the data. The di †usivity of whole hazelnut was determined as a function of drying air temperature and velocity.
1998 SCI.