Simulação de um secador convectivo de bandejas para frutas tropicais.

Abstract

The rapid fruits damage cause, in harvest period, big wastes and, consequenthy, harm to the agriculturist. Some researches point out the fruits drying as one of the conservation methods more economical and efficacious when it is compared with another ones: freeze, tinned, etc. The utilization of dryers optimization procedure aim to obtain more energetical efficiency as well as to perfect the product quality, allowing the decrease of foodstuff final cost. One of the most impediments for the dryers design success is the use of inadequate drying equations. With the advance of numerical methods, became possible the rigorous solution of the differencial equations that represent the drying models. In this work, it was carryed out the drying kinetic simulation of banana slices in thin layer in a convective dryer with fixed bed, with multistages. It was used the BROOKER et alii (1974) equation, as it was the best adjust to the experimental data. The drying constant obtained by the impirical equation of KIRANOUDIS et alii (1997) was optimizated through the nonlinear square minimum methods, using the Levenberg-Marquard modifyed algorithm start of thickness, temperature, velocity and humidity experimental data. The drying model execution was made with differencial and discreted equations. The BDF (Backward Differentiation Formula) numerical method was used to estimate the differential equations for the fruit, while the Finite Difference method was used to discrete the gas equations. These equations represent the mass and energy balances, obtained start the drying general model, proposed by SOKHANSANJ (1984). The drying constant's empiric parameters optimizated was adjusted very well on the available operacional band. The experimental and simulated data was compared in order to legitimate the drying model, obtaining satisfactory results.