Discrete Particle Simulation of Heat Transfer in Pressurized Fluidized Bed with Immersed Cylinders

摘要

The combined computational fluid dynamics and discrete element method (CFD-DEM) has been extended and used in recent years to study heat transfer between bed and an immersed cylinder in fluidized beds at the particle scale. The previous models usually assume the gas flow to be two-dimensional. This does not fully represent the reality in which both the gas motions and particle-gas interactions naturally have more than six degrees of freedom. Here, a full 3DCFD-DEM model is developed to study the heat transfer in 3D gas-fluidized beds with immersed cylinders. For the purpose of the model validation, the simulations are conducted first for a single cylinder under different superficial gas velocities. It is shown that the predicted heat transfer coefficients between the cylinder and bed as a function of superficial gas velocity qualitatively agree with the measurements reported in the literature. The v-shaped curve is also reproduced. Then the simulations are conducted for a fluidized bed with cylinder banks (inline and staggered configurations) at a moderate superficial gas velocity. It is also shown that there is no significant difference in the averaged heat transfer coefficient between inline and staggered arrangements at a moderate superficial gas velocity. This work demonstrates that the developed 3D CFD-DEM approach could be a useful tool to study the coupled flow phenomena and heat transfer in such complex systems.