A diffusional model has been proposed to simulate the drying curves of. hemispherical bodies. The equation representative of the mass transfer in terms of Fick＇s law for a hemispherical shaped body has been solved by separation of variables. By using this solution and the optimization capabilities included irt Microsoft Excel 5.0(TM) spreadsheet, an effective diffusivity coefficient was identified for potatoes at different air drying temperatures (30, 50, 70 and 90 degrees C). Effective diffusivity varied with air drying temperature according to the Arrhenius equation. Experimental data obtained using the same and different experimental conditions of air drying temperature (from 30 to 90 degrees C) and sample size (hemispheres with radius from 0.0128 to 0.0230 m) could be predicted by using the proposed model (%var = 99.7%) The importance of taking into account the real geometry of rite solid was evaluated by using the solution for a spherical shaped body. The model developed for a sphere provided less Satisfactory results in the simulation of tile drying experiments mentioned(%var = 96.6%).