Solar Dryer with Pneumatic Conveyor

The coventional flat bed dryer has the demerit of having nonhomogeneous drying results. Therefore, to obtain nonhomogeneous drying result recirculating type solar dryer with pneumatic conveyor as the recirculating equipment will be. As the grains transported within the penumatic conveyor rapid heat and mass transfer occur resulting in even drying process and make the final results of the drying process homogene. The complete solar dryer was comprised of a feed hopper, centrifugal blower, pneumatic conveyor and a transparent structure acting as drying chamber containing a hopper with vortex at the top. Pneumatic conveyor was used to make recirculation of the grain and to perform continuous drying process. Spherical model was used to predict the drying time.Test with 104 kg of rough rice indicated that the drying time required to reduce the moisture content of rough rice from 28.4% w.b to the final moisture of 14.3% w.b was 5 h. During the test the drying temperature was kept constant at 50.1 oC and RH of 21.73%. The required power for the pneumatic conveyor was 581 W with total energy input of 210.7 MJ including LPG and solar radiation. The resulting drying efficiency was 22.4% with specific energy of 15.2 MJ · kg–1 water evaporated.