Experiments were conducted for yellowed, laminar tissue Nicotiana tabacum L. at air temperatures of 200, 240, 280, and 320°F. A mathematical model, based on a complete energy balance of the leaf tissue, was employed to predict the transient leaf temperature during drying. Close agreement was found between predicted and experimental results for leaf temperature as a function of time during the initial 60% loss of total moisture. However, during the latter stage of drying, thermocouple measurement of the tobacco leaf temperature gave results which were not in agreement with predicted values. It is considered that physiological damage and shrinkage effects caused thermocouple sensing to inaccurately represent average leaf temperature during the latter period. The effects of both air temperature and air velocity on the drying rate were highly significant, with increasing air temperature from 200°F to 320°F resulting in over 300% increase in drying rate. The isothermal drying temperature of the leaf was influenced by the air temperature but was not significantly affected by air velocity.

(Full article published with kind permission from "Tobacco International")