Thin layer drying characteristics of fresh tea leaves

Abstract

Thin layer drying characteristics of fresh tea leaves were investigated to quantify the rate of moisture transfer of fresh tea leaves during the withering process within the temperature range of 20-35 °C, and a relative humidity range of 40-90 % at 1.2 ± 0.3 m/s airflow rate. Five different mathematical models available in the literature were used with the drying data for fresh tea leaves using a constant climatic chamber. Results indicated that the Two-term model gives better predictions for moisture transfer than others. The desorption process of tea leaves occurred in falling rate period. The effective diffusivity of water in tea leaves varied from 3.3409 - 5.4669 × 10-10 m2/s over the temperature range investigated with an activation energy of 1477.75 kJ/kg. The temperature dependence of diffusivity coefficient was described satisfactorily by a simple Arrhenius type relationship.