Development of Turning Devices for Solar Drying of Paddy Rice in the Philippines

Abstract

A previously developed turning device for paddy rice in a solar tunnel dryer consisting of a pivoted metal bar that was pulled longitudinally underneath the basement of the dryer was optimized. New model designs were constructed and tested under field conditions in the Philippines. Seven new configurations of the original device were assessed, which in cluded the amount of bars used (single or double bar), different bar diameters (2.5 or 5 cm), oscillatory or non-oscillatory motion, and two different driving mechanisms: dolly or hand pulling. A method was proposed that was able to assess the efficiency of turning the product during drying. Homogenous layers of colored grains were placed in the dryer while turning procedures were applied. From this data, displacement of colored grains was evaluated for all seven devices. The turning device, which gave the most favorable results for turning efficiency, consisted of a hand-pulled single bar at diameter of 5 cm that induced vertical oscillatory motion. The device significantly improved grain movement in the bulk compared to the six alternative devices. The method proved to be successful for evaluation of turning efficiency of paddy rice in a solar tunnel dryer. The turning device has potential application not only for solar drying, but also any drying process where grains are dried in thin bulk layers, particularly sun drying.