Convective drying of osmo-dehydrated apple slices: kinetics and spatial behavior of effective mass diffusivity and moisture content

• Published in: Heat and mass transfer 2018-04, Vol.54 (4), p.1121-1134
• Main Authors: de Farias Aires, Juarez Everton, da Silva, Wilton Pereira, de Almeida Farias Aires, Kalina Lígia Cavalcante, da Silva Júnior, Aluízio Freire, da Silva e Silva, Cleide Maria Diniz Pereira
• Format: Article
• Language: English
• Subjects: Cartesian coordinates; Convective drying; Dehydration; Diffusivity; Engineering; Engineering Thermodynamics; Heat and Mass Transfer; Industrial Chemistry/Chemical Engineering; Mathematical models; Moisture content; Original; Parameter estimation; Pretreatment; Process parameters; Shrinkage; Spatial distribution; Thermodynamics; Two dimensional models
• ISSN: 0947-7411; 1432-1181
• DOI: 10.1007/s00231-017-2216-z

The main objective of this study is the presentation of a numerical model of liquid diffusion for the description of the convective drying of apple slices submitted to pretreatment of osmotic dehydration able of predicting the spatial distribution of effective mass diffusivity values in apple slabs. Two models that use numerical solutions of the two-dimensional diffusion equation in Cartesian coordinates with the boundary condition of third kind were proposed to describe drying. The first one does not consider the shrinkage of the product and assumes that the process parameters remain constant along the convective drying. The second one considers the shrinkage of the product and assumes that the effective mass diffusivity of water varies according to the local value of the water content in the apple samples. Process parameters were estimated from experimental data through an optimizer coupled to the numerical solutions. The osmotic pretreatment did not reduce the drying time in relation to the fresh fruits when the drying temperature was equal to 40 °C. The use of the temperature of 60 °C led to a reduction in the drying time. The model that considers the variations in the dimensions of the product and the variation in the effective mass diffusivity proved to be more adequate to describe the process.