الفهرس 
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Abstract
This study aimed to : The main goal of this research work is to utilize both natural convection and forced convection drying systems for dehydrating seedless grape during summer season of 2015. Methodology & Results : The experimental work was carried out in a hybrid system of renewable energy includes; solar collector air heater assisted solar modified-quonset dryer, and biogas heat energy for drying seedless grape in addition to compare experimentally between two different solar drying systems ; solar modified-quonset dryer (forced convection mode) and traditional sun drying system (natural convection mode). The results were : 1- The flat-plate solar collector air heater has been operated satisfactorily for approximately six days without any malfunction. For the duration of the experimental work there were 78 hours of bright sunshine of which 54 hours (69.23%) were recorded and utilized in the thermal performance analysis and drying the seedless grape. 2- The hourly average air temperature just leaving the solar collector air heater, air temperature inside the solar dryer (drying air temperature), respectively, was 41.6 and 47.2ºC, while the air temperature outside the drying system was 31.1ºC. Accordingly, the complied data showed that, the solar collector air heater and the solar dryer (modified-quonset form) increased the air temperatures by 10.5 and 16.1°C above the outside air temperature. 3- The biogas heating system provided 4.407 kWh (15.865 MJ) daily average net heat energy during the drying period of which 2.591 kWh (9.328 MJ) heat energy gained by the working fluid (air), resulting in increasing the drying air by 21.9ºC over the inlet air temperature. 4- The drying process helps in reducing the initial moisture content into a level below which deterioration does not occur and the product (raisin) can be stored for a definite period and long shelf life. The initial moisture content of the seedless grape was constituted of 0.8240 gram of water per one gram of wet matter under the two different methods of solar drying. This initial moisture content was reduced to the final moisture contents of 0.1870 and 0.1890 gram of water per one gram of wet matter under the two different methods of solar drying and drying time, respectively. 5- The solar dryer and the traditional sun drying system produced raisin of 7.751 and 7.815 kg of the total fresh grape of 34.020 kg, respectively. Therefore, the two modes of solar drying needed 4.389 kg and 4.353 kg of fresh seedless grape to produce one kilogram of raisin within six and nine days, respectively. The produced raisin of seedless grape under different drying modes had has various colours. They were light brown and dark brown when the grape dried under solar dryer and traditional sun drying method, respectively. Conclusion : The solar dryer (forced convection mode) was operated satisfactory and competitive to the traditional sun drying system (natural convection mode).