Performance evaluation of an automatic solar dryer for grape, fig and plum

In this research, an automatic solar dryer designed and constructed in order to use solar energy for agricultural crops drying. In this dryer water is used as heat transfer fluid. An experiment was carried out in order to investigate the effect of air flow velocity into the drying chamber at three levels (1.5, 3 and 4.5 m/s) on drying time and also the amount of shrinkage of three crops including grape, fig and plum. Results indicated that air flow velocity doesn’t have significant effect on shrinkage, whilst it showed significant effect on drying duration 1 percent level. So with increasing air flow velocity, drying duration is reduced. All tested products with solar dryer, were dried at lower time in comparison with to traditional drying, so drying duration for grape, fig and plum reduced to 49, 52 and 60 percent respectively. Also all the crops have low shrinkage in contrast to the traditional methods, so the shrinkage is reduced 13, 10 and 15 percent at grape, fig and plum respectively.