DRYING CHARACTERISTICS OF HEMISPHERICAL SOLIDS

A diffusional model has been proposed to simulate the drying curves of . hemispherical bodies. The equation representative of the mass transf er in terms of Fick's law for a hemispherical shaped body has been sol ved by separation of variables. By using this solution and the optimiz ation capabilities included irt Microsoft Excel 5.0(TM) spreadsheet, a n effective diffusivity coefficient was identified for potatoes at dif ferent air drying temperatures (30, 50, 70 and 90 degrees C). Effectiv e diffusivity varied with air drying temperature according to the Arrh enius equation. Experimental data obtained using the same and differen t experimental conditions of air drying temperature (from 30 to 90 deg rees 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 simu lation of tile drying experiments mentioned(%var = 96.6%). (C) 1998 El sevier Science Limited. All rights reserved.