Modeling of multiphase heat transfer and transport behaviors of paddy in rotary drum drying by CFD-DEM

Abstract

The application of computational fluid dynamics and discrete element method (DEM) coupling was studied to simulate heat transfer from hot air to a paddy (rice particles) in a rotary drum dryer. The effects of a hot air temperature of 80 °C on various parameters (inlet air velocity (0, 0.5, 1, and 2 m/s), mass feed rate (0.03, 0.05, and 0.07 kg/s), drum rotational speed (10, 20, and 30 rpm), and drum incline (3° and 5°)) were numerically investigated and discussed in terms of heat transfer. The Rocky® DEM and ANSYS Fluent® software packages used one-way coupling to simulate heat transfer from the hot air to the particles in three dimensions of pilot scale rotary drum dryer. At the end of the residence time (45 s), the increase in the inlet air velocity from 0.5 to 2.0 m/s increased the average particle temperature from 36.4 °C to 48.7 °C. A rotation speed of 10 rpm increased the average particle temperature by 7.7 °C compared to 30 rpm. The decrease in the drum inclination angle from 5° to 3° extended the average particle residence time by 27 %. The increase in the mass feed rate prolonged the residence time, resulting in an increase in the average particle temperature.

Keywords

• Rotating drum
• Rotary dryer
• Discrete element method (DEM)
• Computational fluid dynamics (CFD)
• Heat transfer