A Packed bed solar air heater-cabinet type dryer

64 7. SUMMARY Medicinal and aromatic plants that have been growing wild in hot and mild climates have significant export potential for Turkey. The mechanisation applications for the production of the standard species of these crop groups can be refreshed agriculture sector of Turkey. In traditional production methods of medicinal and aromatic plants that are still picked up from nature are dried under the sun and on the ground. This method causes the crop loses that is about 40%. The chroma, essential oil and some important properties of crop are badly effected during this process. In addition to, foreign materials such as dust, hair, insect and mould mix to the crop. The crops that are produced in this way have no market potential. For these reasons the harvest problems of medicinal and aromatic crops must be solved primarily. In this group of crops, 58% of the total production cost are spent for drying where 45% of this are fuel cost. To reduce the fuel costs and to avoid the environmental pollution because of fossil fuels, the energy needed for drying could be supplied from the sun. The solar energy potential available of Turkey is very suitable for this purpose. During the harvest time of these crops the solar radiation is very intensive which means the drying could be carried out by usage of solar energy In this study a packed bed solar air heater and cabinet dryer combination were used to dry medicinal and aromatic crops. During the experiments, it's determined that the temperature difference between the dryer and ambient air was among 9 to 17°C. The mean dryer inlet temperature was among 41 and 49°C. In this research, drying rates of solar dried crops were found faster than sun dried proâusrti. Qrigmmm uw/hw, Mmtlm ptmrit® «wl jfotmtiHmm §Apmm were «M#d S to 4, 2,6 and 18 times faster than sun dried crops. Because of the hue distortion and increased brightness of the products, the green colour of sun dried products turned to65 light yellow - light brown that is undesirable in the market. In comparison to, the solar dried crops were not faced with these negative effects. Essential oil losses were determined as 1 to 4%, 20 to 30% and 10 to 23% in the shade, sun and solar dried crops respectively. Essential oil losses of sun dried products were determined 1,3 to 15 times more than solar dried products. The essential oil losses in the Mentha piperita were 12,6% and 1,2% in the sun and solar dried products respectively. The results show that the essential oil losses of sun dried Mentha were 15 times greater than solar dried products. As a conclusion, traditional drying methods of medicinal and aromatic crops are inadequate, because they need much more time and cause chromatic distortion and essential oil losses. By using the packed bed solar air heater, it was possible to reach the suggested temperature range for the drying of medicinal and aromatic plants.