A liquid diffusion model to describe drying of whole bananas using boundary-fitted coordinates

• Liquid diffusion model were used to describe drying of whole bananas.
• Diffusion equation was solved using generalized coordinates.
• Optimizer was developed to determine thermo-physical properties.
• A model including shrinkage and variable mass diffusivity describes drying adequately.

This article uses a liquid diffusion model to describe convective drying of whole bananas. The experiments were carried out with drying air temperatures at 40, 50, 60 and 70 °C. A two-dimensional numerical solution in generalized coordinates of the diffusion equation with boundary condition of the third kind, obtained through the finite volume method, was used to describe the process. A structured non-orthogonal grid was obtained by digitization of the photography of the fruit. In order to determine the thermo-physical properties, an optimizer was coupled with the numerical solution. The model proposed in this article, which includes shrinkage and variable effective moisture diffusivity, well describes drying for all the experimental conditions, and makes it possible to predict the moisture distributions at any given time. The determination coefficients were greater than 0.99970 and the chi-squares were less than 8.33 × 10−4.