Experimental investigation and mathematical modeling of drying of green tea leaves in a multi-tray cabinet dryer

Abstract

Although many experimental investigations have been carried out on the drying of foodstuffs in the tray dryers, little detailed analysis is available in the literature on the mathematical modeling of simultaneous heat and mass transfer in these types of dryers. In this work, drying behavior of green tea leaves was investigated in a multi-tray cabinet dryer. A mathematical model was developed for prediction of the moisture content and temperature of green tea leaves and also the humidity and temperature of the drying air, in the trays of the dryer. Each tray was considered as a fixed bed of tea leaves. The proposed model was solved, after dividing the bed into a series of thin layers, using a finite difference method and a trial and error technique. Equilibrium moisture contents and moisture diffusivity values, used in the mathematical model, were estimated and correlated for the green tea, used in this study. The predictions of the model showed a good agreement (MRE lower than 5%) with the experimental data, obtained from drying of green tea leaves in a domestic three-tray dryer at 60 and 70 °C. The effect of drying air velocity, temperature and the number of the green tea leaves in each tray was investigated on the drying behavior of green tea in the dryer.