Investigation the influence of variety, temperature and air velocity parameters in qualitative performance of a thin layer paddy dryer

Given the importance of drying process in the rice production, influence of different drying temperatures (40, 50 and 60 °C) and air velocity (zero, 2.65 and 4 m/s) on drying time and the percentage of broken grains were investigated in a thin layer dryer for three Tarom, Jelodar and Fajr varieties. The results for Tarom variety showed that by increasing the drying temperature from 40 to 60 °C, drying time was decresed by the average of approximately 55%, whereas the percentage of broken rice grains increased equal to 50%. Drying time for the varieties having medium grain length was less than that of the long grain varieties, due to the less convection surface area and thicker rice husk. Meanwhile varieties having medium grain length indicated higher resistance to crack due to the grain structure. On the other hand, the hot air flow with suitable velocity not only reduced the drying time, but also significantly decreased the crack percentage. Based on the results of this study, air flow velocity of 2.65 m/s relative to the flow velocity of 4 m/s indicated a significant influence on reducing the crack percentage, especially in the drying temperature of 50 °C.