Solar drying of some agricultural products under Fayoum climate

Two similar solar drying units were designed and constructed for drying peppermint and basil leaves under Fayoum conditions at two periods in August, 2014 for peppermint (Mentha viridis L.) form 11 to 14 August, 2014 and for basil (Ocimum basilicum L.) from 21 to 24 August, 2014. Each drying unit consists of a solar collector, which oriented and tilted at latitude tilt angle (30o) and attached with drying chamber. The drying experiments were carried out to examine the effect of peppermint and basil leaves depths (2, 4 and 6 mm) and airflow rates (0.015 and 0.025 m3.s-1) on peppermint and basil leaves drying rate. The obtained results indicated that, the tilted surface of the solar collector increased the amount of the total daily average solar radiation by 24.59% and 25.51% for the first and second drying periods of peppermint and basil leaves, respectively. The higher outlet air temperatures (drying temperature cycles) were obtained at the lower airflow rate (0.015 m3.s-1) and vice versa. The values of solar energy gained and the thermal efficiency of the solar collector were relatively higher at the higher airflow rate as compared with those for the lower airflow rate.