Abstract
Artificial methods are mainly used for grain drying in developed countries, but most developing countries rely on natural drying traditionally. The purpose of this study is to improve the quality during sun drying. Using heat balance, drying characteristics of a thin layer of rough rice under solar radiation was investigated. More than 90% of energy absorbed by rough rice was released to ambient air, and only a little percentage was used for moisture vaporization. Effects of integrated and instantaneous radiation on drying rate were reported. Ratio of cracked rice increased by the average temperature of grain surface, and more than 20% of cracked rice was observed even when the grain surface radiation temperatures was kept under 34°C.
