Design, construction and performance evaluation of a solar drying unit of basil leaves / [electronic resource].

Includes references.

Two similar solar drying units were designed, constnu.:ted and evaluated for drying basil leaves (Ocimum basi/icum 1.) as a medicinal and aromatic plant at initial moisture content of 590.73% (d.b) or 85.52%
(w.b) under Fa;voum conditions by using heated air. Each d,)'ing unit consists ofa flat-plate solar collector. which oriented and tilted with an optimum tilt angle and. attached with drying chamber. The drying experiments were carried out to examine the effect of basil leaves thicknesses (2, 4 and 6 cm) and airflow rate (0.015 and 0.025 m3.sec·') on the basil leaves drying rate. The obtained results indicated that the daily average total solar radiation flux incident on the tilted solar collector surface (29.30 MJ m·'1.daf') was greater than that incident on the horizontal surface (24.30 MJm·'1.daJ'-') by 24. 58%. The output higher air temperatures were obtained at tlie lower airflow rate whereas; the energy gained to the air from the solar collector was relatively higher at the higher airflow rate as compared with the lower airflow rate. Consequently, the solarco/lector with the higher airflow rate increased the overall thermal efficiency by 5.46% as compared to the lower airflow rate. The moisture content ofdried basil leaves was strongly affected by the basil leaves thickness and the airflow rate. The final moisture content ofdried basil leaves rangedfrom (lJ.52% to 14.58% d.b) depending on the drying temperature cycle. Very small changes were observed in the colour and shape of heated-air dried basil leaves as compared to that dried at direct sun rays. The essential oil contents of dried basil leaves were slightly higher for the drying unit with the higher airflow rate as compared with the corresponding values obtained from the drying unit with the lower airflow at all basil leaves thicknesses.While on Contrast, total chlorophylls contents were slightly higherfor the
drying unit with the lower airflow rate as compared with the
corresponding values obtained from the drying unit with the higher
aiifl9w at all basil leaves thicknesses. Effect of the individual variables
(aiiflow rate, basil leaves thickness. moisture removed. and their
interactions) on the drying rate was statistically analyzed Under the
conditions of this study, the optimum depth to dry basil leaves by using
heated air is 4 em.

Summary in Arabic.