Investigation of Parboiled Paddy Behavior and Drying Conditions in Impinging Stream Dryer via CFD-DEM Simulation

This research presents the development of computational fluid dynamics model combined with discrete element method (CFD-DEM) for investigating the parboiled paddy behavior and drying conditions in an impinging stream dryer (ISD) during the falling drying rate period with a parboiled paddy feed rate of 320 kgdry mass/h, impinging distance of 5 cm, air temperature of 190 o C, parboiled paddy diameter 3.9 mm, parboiled paddy initial moisture content 0.5 d.b., parboiled paddy initial temperature 28 o C and various air velocities (15, 20, 25 m/s). In each drying condition, there were 17 drying cycles. The simulated results showed that the number of oscillations of parboiled paddy in the impinging zone and the parboiled paddy penetrated to the opposite pipe increased with an increase in air velocity. An increase of air velocity led to the increase of parboiled paddy velocity and momentum in the pipe of impinging stream dryer. The parboiled paddy distribution in drying chamber also increased with an increase in air velocity. They led to the longer mean residence time, therefore mean moisture content of parboiled paddy was lower and mean temperature of parboiled paddy was higher. To compare the simulated and experimental results, the simulated results revealed that the predicted mean moisture content and mean temperature of parboiled paddy with CFD-DEM model were close to the experimental results with R2 of 95% and 97%, respectively.