Diffusion coefficient estimation difficulties at the beginning of drying experiment

Abstract

The aim of this paper is to determine the error of the diffusion coefficient of removed moisture applying convection drying of carrot slices. In this study series for diffusion coefficient calculation are applied and the diffusion coefficient error at the beginning of the experiment is investigated. The experiments were carried out with carrot slices of 15 mm thickness on laboratory conditions. There are compared drying processes by different drying temperatures with the purpose to investigate the temperature effect on the diffusion coefficient changes. Using the experimental data the theoretical diffusion coefficient was calculated using iterative methods with small drying time. The research shows that one should be careful when using the first term of solution of the Fick's second law of diffusion, although in practice only the first term of the series is often applied. The results of this research showed that the error of the diffusion coefficient occured due to several members of series at small times. The theoretical results are useful for description and modelling of the drying process with the time dependent diffusion coefficient for carrot slices and pieces on two- and three-dimensional case. The calculated parameters can be used for further research work and for improvement of the whole drying process.