Abstract
Gravity flowing beds of particles are widely found in chemical engineering industries, where the particle flow and heat transfer inside are very important for high efficiency and safe operations in the relevant facilities. In the present study, the particle flow around a circular or elliptical tube is numerically investigated with the discrete element method (DEM), where the particle flow and heat transfer in different zones around the tube are carefully analyzed. According to the particle flow and geometric characteristics of the tube, eight particle flow zones are established around the tube. It is found that the pore structure, contact number and velocity of particles in different particle flow zones are different due to the size of the stagnation zone and cavitation zone at the top and bottom of the tube. Compared with the circular tube, the porosity in the region of R < 2 dp outside the elliptical tube is smaller in zone 1, 3 and 4. The contact number in zones 3 and 4 are almost 1.3 and 1.5 times of that of the circular tube respectively, and the particle velocity in the stagnation zone is larger. Finally, based on the flow characteristics of particles around the two kinds of tubes, the heat transfer performance of the two kinds of tubes in different zones is analyzed. Due to the improvement of flow performance around the elliptical tube, the heat transfer performance of the elliptical tube is better than that of the circular tube.
