Multiscale investigation of tube erosion in fluidized bed based on CFD-DEM simulation

A multiscale analysis on the erosion of the immersed tubes in a 3-D fluidized bed is conducted using computational fluid dynamics-discrete element method (CFD-DEM) coupling a particle-scale erosion model referred to as the shear impact energy model (SIEM). Different gas velocities and tube shapes are adopted to obtain more information. Several hydrodynamic parameters, including the void and solid fraction, the average particle speed, the granular temperature and the fluctuation energy (defined as the sum of the granular temperature) have been obtained and analyzed. Since the hydrodynamic properties have great effect on erosion of the immersed tube, a quantitative analysis was carried out based on the hydrodynamic parameters around the tubes. An intrinsic relation between erosion on the immersed tube and the fluctuation energy has been revealed based on the analysis, which indicates that the fluctuation energy of the particles near the tube probably is the main reason for the erosion. Moreover, the ordered motion of the particles also has some effect on the erosion, especially on the erosion of the top and bottom of the tube when the gas velocity is high.