Drying moringa leaves and flowers using a tunnel dryer: Experimental study and modeling of drying kinetics

This work highlights the use of an indirect trapezoidal tunnel solar dryer for moringa drying. We sampled moringa leaves and flowers harvested in the Dakar region. Tests were carried out over two days, between 11 a.m. and 4 p.m. under real conditions. Drying conditions varied from an average irradiance of 530 W/m² on the first day to 700 W/m² on the second. The average air temperature inside the dryer varied from 35°C on the first day to 49.5°C on the second. Mass loss results obtained by weighing showed a more rapid variation in mass loss for leaves than for flowers. We plotted experimental curves of reduced water content against drying time, approximating them using empirical or semi-empirical models from the literature. Model selection criteria were defined, and the Page and logarithmic models gave correlations of 0.99859 and 0.96463, respectively. The effective diffusivity (D_eff) for both products was evaluated by fitting experimental data to the Crank diffusion equation. Expressed in terms of the logarithm of reduced moisture, the following D_eff values were obtained:

Leaves: D_eff ranged from 8.12135.10^-10   to 9.16675.10^-10 m²/s.

Flowers: D_eff ranged from 1.38899.10^-9 to 1.41385. 10^-9 m²/s.

These values indicate the rate at which moisture diffuses through the plant material under the specific conditions of the experiment.