Drying characteristics and modeling of tomato thin layer drying in combined infrared-hot air dryer

Abstract

In this study tomato slices were dried with three thicknesses (3, 5 and 7 mm), three temperatures (60°C, 70°Cand 80°C) and air speed of 1.1 ms^{-1 in} a combined infrared-hot air dryer.  Distance from infrared source was 70 cm, while, input air temperature was 60°C.  The experiment was conducted as factorial based on a completely randomized design.  Results showed that energy consumption reduced along with the increase in temperature and slice thickness.  Decrease in the slice thickness from 7 to 3 mm resulted in a significant decrease in drying time.  Maximum diffusion coefficient was related to the thickness of 7 mm and the temperature of 80°C, while, the minimum value was related to the thickness of 3 mm and the temperature of 60°C.  Effective diffusion coefficient and activation energy is, respectively, 9-10 m² s^-1 to 10-11 m² s^-1 and 12.7-110 kJ mol^-1.  Middili's model had the maximum R² and the minimum RMSE and SSE at different temperatures and speeds, thus, it was considered as the fittest model to predict the moisture.