Modelling the carrot thin-layer drying in a semi-industrial continuous band dryer

Abstract

This paper presents a mathematical modelling of the drying process in a semi-industrial continuous band dryer. Carrot slices with the thickness of 5 mm were used for the drying experiments. The experiments were conducted at three air temperatures, 50, 60, and 70°C, three air velocities, 0.5, 1.0, and 1.5 m/s, and three chain linear velocities, 2.38 × 10<sup>–4</sup>, 2.78 × 10<sup>–4</sup>, and 3.33 × 10<sup>–4</sup> m/s with three replications for each treatment. The Lewis, Henderson & Pabis, and Page models were fitted to the experimental data of the moisture ratio against the sample position using non-linear regression analysis by MATLAB computer program. The models were compared based on their coefficients of determination (R<sup>2</sup>), root mean square errors (RMSE), and reduced chi-squares (χ<sup>2</sup>) between the experimental and predicted moisture ratios. Consequently, the Page model was selected as the best mathematical model for describing the drying kinetics of the carrot slices. The correlations of the Page model constants k and m with the variables T, U<sub>a</sub> and U<sub>c</sub> were determined. The effective moisture diffusivity varied from 3.21 × 10<sup>–7</sup> to 8.98 × 10<sup>–7 </sup>m<sup>2</sup>/s. The energy of activation varied from 23.02 kJ/mol to 28.1 kJ/mol using Arrhenius type equation.