Performance of a Mixed-Mode Type Solar Crop Dryer in Drying Rough Rice Under Natural Convection

摘要

The performance of a three-shelf mixed mode type solar crop dryer was analyzed in drying rough rice. The dryer had a collector area of 1.74 m~2 and the area of each shelf was 0.81 m~2 (900mm×900 mm). Tests were conducted with alternately loading all the three shelves, two shelves, and a single shelf with varying (33-110 mm) depths of grain beds. The three and two shelves tests were conducted with partial loading of the shelves, keeping approximately 10 % area of each shelf grain free along the width of the dryer and alternating the back and front ends of the adjacent shelves. This procedure helped to create an S-shaped path for easy movement of the drying air. All these tests showed that single/double shelf tests with complete loading the shelf area increased the energy utilization efficiency of the dryer. Keeping the grain free space for easy movement of drying air reduced the energy utilization efficiency of the dryer. The drying capacity of the dryer was 1.75 kg/(hm~2) of wet rough rice under natural convection although the air temperature rose by some 15 ℃ before passing through the grain bed. This indicated that the dryer needed an air moving device in order to increase the drying perfor-rnmance.