Modeling of thin layer drying of tarragon (Artemisia dracunculus L.)

The drying behavior of tarragon leaves as well as chopped plants were evaluated at air temperatures ranging from 40 to 90 °C, at various air relative humidities and a constant air velocity of 0.6 m/s. The experimental data was fitted to a number of thin layer drying equations. The equations were classified to select the more relevant one. Three equations were selected and the coefficients of the equations were compared by three statistical parameters as residual sum of squares, standard error of estimate and mean relative deviation. The effect of temperature on the coefficients of the three selected equations was evaluated by nonlinear regression. The results show that higher temperature cause shorter drying time. Separated leaves have shorter drying time compared to chopped plants. Although the Diffusion approach equation showed the best fit, the Page equation was selected, since it had almost a similar performance but the equation is simpler with two parameters instead of three. Then a function was derived describing the relationship between the two parameter values and drying temperature.