Comparison of boundary conditions to describe drying of turmeric (Curcuma longa) rhizomes using diffusion models

Abstract

Turmeric is harvested with high moisture content and should be dried before the storage. It is observed that drying is quickest when the rhizomes are peeled and cut in small cylindrical pieces. In order to describe the process, normally a diffusive model is used, considering boundary condition of the first kind for the diffusion equation. This article uses analytical solutions considering boundaries conditions of the first (model 1) and third (model 2) kinds coupled to an optimizer to describe the drying process. It is shown that, for model 1, the fit of the analytical solution to the experimental data is biased, despite the good statistical indicators (chi-square χ 2 equal to 1.7095×10 −3 and coefficient of correlation R 2 of 0.9988). For model 2, the errors of the experimental points about the simulated curve can be considered randomly distributed, and the statistical indicators are much better than those obtained for model 1: χ 2 03.5596×10 −4 and R 2 00.9996.

Comparison of diffusion models for description of osmotic dehydration of radish slices dipped in brine

“…In the literature, diffusion models with boundary condition of the first kind are mostly used to explain convective drying (SILVA et al, 2009;DA SILVA et al, 2012;SILVA et al, 2012;DOYMAZ, 2013) and also osmotic dehydration of agricultural products (QUEIROZ et al, 2010;SOUZA SILVA et al, 2011;MERCALI et al, 2011;HERMAN-LARA et al, 2013). Overall, the boundary condition is derived from the agitation condition of the environment within which a particular product is immersed.…”

“…As stated by DA SILVA et al (2012) and SILVA et al (2013), the analytical solution of diffusion equation in cylindrical coordinates under the above-mentioned assumptions can be obtained by separation of variables and results in:…”