Modeling of drying thin layer of tomato slices using solar and convective driers

Abstract

This paper presents a mathematical modelling of thin layer drying of tomato (Solanum lycopersicum L.). To this end, two different methods are used to dehydrate tomato slices namely the solar drying (in an indirect solar dryer), and the forced convective drying (in a convective dryer). In the solar dryer, the experiments are carried out at a constant air velocity of 1 m/s and average temperatures of 37.2, 39.9, 42.5 °C. In the convective dryer, the experiments are performed with five different temperatures (30, 40, 50, 60 and 70 °C) at a constant air velocity of 1 m/s. In order to estimate and select the appropriate drying curve equation, fifteen different thin layer mathematical drying models available in the literature are applied to the experimental data. The models are compared using the correlation coefficient (r) and the standard error (s) and are predicted by a non-linear regression analysis using the Curve Expert software. The Midilli-Kucuk model shows a better fit to the experimental drying data according to (r) and (s) for the two drying methods. The effect of the drying temperature on the parameters of this model is also determined. The experimental drying curves show only a falling drying rate period. On average, tomatoes are dried until the moisture content of 0.15 kg _water/kg _{dry matter} from 14.36 kg _water/kg _{dry matter} in the solar drying, and to the moisture content of 0.10 kg _water/kg _{dry matter} from 12.66 kg _water/kg _{dry matter} in the convective drying.