Heat transfer and erosion mechanisms of an immersed tube in a bubbling fluidized bed: A LES-DEM approach

Particle-scale modeling of the gas-solid motion in a bubbling fluidized bed is conducted to explore the heat transfer and erosion mechanisms of an immersed tube. Heat transfer and erosion quantities around the tube are obtained to analyze the critical factors affecting their distributions. The results indicate that vigorous particle stream washes against the top and bottom of the tube, resulting in the formation of a halo and a stagnated cap in these two regions, respectively. Instantaneous heat transfer coefficient oscillates in a complex way with the solid velocity and concentration near the tube surface. The non-uniform time-averaged heat transfer coefficient around immersed tube is a combined effect of local solid velocity and concentration. Total heat transfer flux is mainly occupied by the convective heat flux. Moreover, erosion distribution can be identified from the circumferential distribution of solid flux. Increasing the superficial velocity enlarges the local heat transfer coefficient and the erosion quantity. (C) 2015 Elsevier Masson SAS. All rights reserved.