Author(s)

Wilton Pereira da Silva^*, Cleide Maria Diniz Pereira da Silva e Silva, Jürgen Wolfgang Precker, Josivanda Palmeira Gomes, Pedro Luiz Nascimento, Laerson Duarte da Silva

Federal University of Campina Grande, Campina Grande, PB, Brazil.

This article compares diffusion models used to describe seedless grape drying at low temperature. The models were analyzed, assuming the following characteristics of the drying process: boundary conditions of the first and the third kind; constant and variable volume, V; constant and variable effective mass diffusivity, D; constant convective mass transfer coefficient, h. Solutions of the diffusion equation (analytical and numerical) were used to determine D and h for experimental data of seedless grape drying. Comparison of simulations of drying kinetics indicates that the best model should consider: 1) shrinkage; 2) convective boundary condition; 3) variable effective mass diffusivity. For the analyzed experimental dataset, the best function to represent the effective mass diffusivity is a hyperbolic cosine. In this case, the statistical indicators of the simulation can be considered excellent (the determination coefficient is R² = 0.9999 and the chi-square is χ² = 3.241 × 10^–4).

Optimization; Convective Boundary Condition; Diffusion Model; Finite Volume Method

Silva, W. , Silva e Silva, C. , Precker, J. , Gomes, J. , Nascimento, P. and Silva, L. (2012) Diffusion models for the description of seedless grape drying using analytical and numerical solutions. Agricultural Sciences, 3, 545-556. doi: 10.4236/as.2012.34065.