Effective Moisture Diffusivity Modeling of Sweet Lemon Slices

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Thin layer drying behavior of sweet lemon slice was experimentally investigated in a convective type dryer and the mathematical modeling performed, using thin layer drying models given in literature. Drying experiments were conducted at inlet drying air temperatures of 40, 50, 60, 70 and 80 ?C; two slice thicknesses of 3 and 6 mm, and, at one drying air velocity of 0.5 m/s with three replications in each treatment. Page model was employed (according to their coefficients of correlation) to estimate the drying curves. The effects of drying air temperature on the model constants and coefficients were evaluated through a non-linear regression technique. The accuracy of the model was estimated according to three statistical parameters of: coefficient of determination (R2), Chi-square (?2) and Root Mean Square Error (RMSE). Results indicated that Page model could satisfactorily describe the drying curve of sweet lemon slices with R2=0.99812, (?2) =0.0000518 and RMSE=0.003912 for a thickness of 3 mm while R2=0.997776, (?2) =0.0000715 and RMSE=0.0082232 for a thickness of 6 mm. Moisture transfer from the slices was described by applying Fick’s diffusion model. The effective diffusivity coefficient values changed from 8.04×10-9to 7.63×10-8 m2/s for the range of temperatures considered. An Arrhenius relation with an activation energy value of 28.53 kJ/mol and the diffusivity constant of 5.01×10-4 m2/s for a thickness of 3 mm, while 39.46 kJ/mol along with a diffusivity constant of 9.37×10-4 m2/s for a slice thickness of 6 mm, were obtained, indicating the effect of drying air temperature and slice thickness on the diffusivity parameter.

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