Drying description of cylindrical pieces of bananas in different temperatures using diffusion models

Abstract

Three diffusion models were used to describe drying of bananas cut into cylindrical pieces. Analytical solutions of the diffusion equation with boundary conditions of the first and third kind were used to describe the process. In the drying experiments using hot air, the cylindrical pieces had the following dimensions: length of about 21mm and radius of 15mm, on average. The drying air temperatures were 40, 50, 60 and 70°C. To determine the process parameters, an optimizer was coupled to the analytical solutions. For the best model, the effective mass diffusivities were 2.53×10−8; 3.12×10−8; 6.19×10−8 and 7.32×10−8m2min−1, while the convective mass transfer coefficients were 1.93×10−5; 3.04×10−5; 3.18×10−5 and 4.97×10−5mmin−1. The determination coefficients were greater than 0.9990 and the chi-squares were less than 5.3×10−3 for all simulations of the experiments.