الفهرس 
Chapter I: IntroductionOnly 14 pages are availabe for public view
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Abstract
In this study, an investigation of a pilot- scale hybrid solar dryer powered by solar energy as well as fossil energy for herbs and vegetables was carried out.
In the pilot- scale study three different runs on three different herbs were studied. The first run was performed on Coriander which has been dried from initial moisture content of 90% to 33% in 28 hours (effective drying time), while the second run was performed on two herbs, Parsley and Spearmint which has been dried from initial moisture content 86% to 17.5 % and from initial moisture content of 86% to 21.1 % respectively in 24 hours (effective drying time). The final run was performed on Basil which has been dried from initial moisture content of 85% to 14.5% in 23 hours (effective drying time).
A mathematical model for the hybrid drying process was developed. Based on the developed model, A MATLAB software presented as Graphical user interface (GUI) format was designed to simulate the drying process. The validity of the model and the software was evaluated by comparing the experimental results with the predicted results calculated by the software. A reasonable agreement was found between experimental and predicted results. The performance of the model was measured using absolute percentage error (APE) which is 4 %.
After that a full scale hybrid solar drying system (with capacity up to 1200 kg) was implemented and tested on full load mode. In the full scale, three more runs were performed using Chamomile which has been dried from initial average moisture content of 82 % to 14.2 % in time from 14-18 hours and a sample was taken and analyzed. The essential oil content was found to be 0.8 ml/100 g compared to the maximum obtained value of 0.4 to 0.5 ml/100 g that could be attained using sun drying.
The system proved its validity in full scale and proved good quality of the product compared with natural sun drying techniques.
For all herbs that used in this study, the drying rate curve behaviors were studied and it was found that the constant falling rate period was not detected and all the drying operation was performed in the falling rate period only. Then the drying rates of these herbs were compared to each other and it was found that Spearmint has the highest drying rate while, Chamomile has the lowest drying rate among the studied herbs.