الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
It is known that the natural convection (NC) solar drying process is a simple and cheap method for drying food stuff but it is not preferable for common users in case of drying high moisture content agro-products due to the slow rate of drying, meanwhile, the forced convection (FC) drying process is most appropriate for such products but its economic feasibility may be affected due to high initial and maintenance costs. Therefore, the present study proposed a controlled natural convection (CNC) drying mode using a solar greenhouse dryer (SGD) for drying grapes as a simple and inexpensive domestic dryer instead of the commonly forced convection SGD. The new CNC drying mode using Plexiglas-SGD showed a higher drying rate than the NC mode and is close to the FC mode. The CNC mode using Plexiglas-SGD reduced the initial moisture content of grapes from 5.91 g water/g dry matter to the final moisture content of 0.15 g water/g dry matter in 12 h with thermal drying efficiency of 12.5%, in return, it was 15 h and 9.7%, respectively for NC mode. Page model is found to be the most appropriate model to predict the kinetics of SGD under all drying modes regardless of the cover’s type. The new CNC drying mode using Plexiglas -SGD achieved the lowest cost per 1 kg of dried grapes (1.26 $/kg), the highest total saved costs over the lifespan of the dryer (245.46 $) and the shortest payback period (1.08 years) compared to the other two dryers, NC-SGD and FC-SGD. Thus, the Plexiglas-SGD using the new drying mode of CNC is a promised alternative method to avoid the drawbacks of FC and NC drying modes for drying the high moisture content products.