30F-13 |
Mathematical modelling of water effective diffusivity during papaya drying |
M. A. GARCÍA-ALVARADO1, M. A. Salgado-Cervantes, G. C. Rodríguez-Jimenes, L. Lagúnez-Rivera, and J. De La Cruz-Medina. (1) UNIDA, Instituto Tecnológico de Veracruz, Av. Miguel Angel de Quevedo 2779, P.O. Box 1420, Veracruz, 91860, Mexico There are two tendencies in mathematical description of food particles drying. The rigorous modelling, in which the heat and moisture transfer equations with variable properties were used, and the simplified modelling, in which only moisture transfer with constant properties was considered. In this work an intermediate consideration was introduced for mathematical description of papaya slices drying. The model introduced is an analytical solution of moisture transfer equation in which the shrinkage was tacked in account. Experimental convective drying kinetics of 3 X 5 cm papaya slices were developed at 50, 60 and 70 C of air temperature, 0.5, 0.75 and 1 m/s of air velocity, and 0.25, 0.5 and 0.75 of slice thickness. The drying results for 0.75 cm thickness slices, 1 m/s air velocity and the three temperatures were fitted to the model by non-linear regression. The fitted parameters were Do and activity energy (E) for Arrhenius equation of water diffusivity, and the exponent of a exponential model for the shrinkage at the end of drying. The model proposed fitted with 1/3 of the experimental results can reproduce the whole of the experimental drying kinetics. The water diffusivities obtained were between 7.134 X10-10 and 10.09 X10-10 m2/s. The final shrinkage was between 0.5 and 0.7 of the initial slice thickness. The model suggested in this work introduces the shrinkage in a simple algebraic model. From this model it is feasible to deduce variable mass transfer coefficient for drying process simulation.
Session 30F, Food Engineering: Transport processes and kinetics
|