Two identical prototype solar dryers (direct and indirect) having the same dimensions were used
to dry whole mint. Both prototypes were operated under natural and forced convection modes.
In the case of the later one the ambient air was entered the dryer with the velocity of 4.2 m s1.
The effect of flow mode and the type of solar dryers on the drying kinetics of whole mint were
investigated. Ten empirical models were used to fit the drying curves; nine of them represented
well the solar drying behavior of mint. The results indicated that drying of mint under different
operating conditions occurred in the falling rate period, where no constant rate period of drying
was observed. Also, the obtained data revealed that the drying rate of mint under forced convection
was higher than that of mint under natural convection, especially during first hours of
drying (first day). The values of the effective diffusivity coefficient for the mint drying ranged
between 1.2 · 1011 and 1.33 · 1011 m2 s1.