Application of superposition technique for modeling drying behavior of avishan (Zataria multiflora) leaves.

摘要

Drying curves of agricultural products at different air temp. and air velocities are often identical in shape, but shifted along the abscissa. The shift distance for each curve measured relative to a chosen reference curve is called the shift factor. This allows the drying curves to shift horizontally along the time axis through a time multiplier (shift factor) until a smooth master curve is created. The master curves can be used to address air temp. and air velocity effects on drying kinetics by using the shift factors. Validity of this method, termed the time-temp. superposition technique (TTST), was determined to model the effects of air temp. and air velocity on drying kinetics of avishan leaves. Drying data at 3 air temp. (30, 40 and 50 degrees C) as well as 3 air velocities (0.5, 0.8, 1.2 m/s) were used for modeling. Results showed that the TTST was adequate to generate a moisture ratio master curve for avishan leaves. The resulting master curves represented by the Page model (R2 > 0.996) and its validity to predict the moisture ratio of avishan leaves were compared with a regression model. The master curve model performed better than the regression model in predicting the moisture ratio of avishan leaves as a function of air temp. and air velocity. This result confirmed the applicability of TTST for determining the activation energy of avishan leaves.