الفهرس 
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Abstract
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. The final average moisture content of peppermint leaves were 12.97 % (d.b.) and 12.88 %(d.b.) at the airflow rates of 0.015 and 0.025 m3.s-1, respectively. While the final average moisture content of basil leaves were 13.22 % (d.b.) and 11.52 % (d.b.) at the airflow rates of 0.015 and 0.025 m3.s-1, respectively. The drying effectiveness had less value at all peppermint and basil leaves depths at airflow rate of 0.025 m3.s-1 than those at air flow rate 0.015 m3.s-1. The 4-cm plant leaves depth had the least values of drying effectiveness (0.242 and 0.172 h/g moisture) at airflow rate 0.025 m3.s-1 for peppermint and basil leaves, respectively. Two equations were developed by the Excel-2010 soft-ware to obtain the relationship between drying rat (g moisture/h) and leaves depth at two airflow rates (0.015 and 0.025 m3.s-1) for peppermint and basil. All the depths of peppermint and basil leaves dried by heated air using solar energy had higher total chlorophyll (mg/100g) than the same depths of peppermint and basil leaves dried directly by the sun (natural drying). On the contrary, all depths of peppermint and basil leaves dried by heated air using solar energy had less oil content (%) than the same depths of peppermint and basil which dried directly by the sun (natural drying). Under the condition of this study, it can be concluded that, the optimum depth for drying medicinal and aromatic plants in the solar dryer is 4 cm.