Particle Scale Modelling and Analysis of Fluid Flow and Heat Transfer in Fluidised Beds

摘要

Fluid bed reactors have been extensively used in chemical processes due to their high heat transferefficiency. Typical examples are ironmaking blast furnace which involves complicated multiphaseflow, heat transfer and chemical reactions in a packed bed, and fluidized bed combustors whoseperformance heavily depends on the hydrodynamics and thermal-chemical behavior of particles ininteraction with gas. To achieve optimal design and control of such a fluid bed reactor, it isimportant to understand the flow and heat transfer characteristics. Particle scale studies, achieved bythe use of approach of coupled discrete element method (DEM) and computational fluid dynamics(CFD) [1, 2], are useful to achieve this goal. In this approach, the motion of discrete particles isobtained by solving Newton's second law of motion, and the flow of continuum fluid by solving theNavier-Stokes equations based on the concept of local average as used in CFD, with the coupling ofCFD and DEM through particle-fluid interaction forces. This approach has recently been extendedto study heat transfer in gas fluidization [3]. It considers different heat transfer mechanisms indetail, including, for example, particle-fluid convection, particle-particle conduction, and particleradiation. The proposed model offers a useful numerical technique to elucidate the fundamentalsgoverning the heat transfer in packed/fluidized beds at a particle scale. Here our major applicationof this approach is summarized below.