关键词: 计算颗粒流体力学, 流化床, 传热, 颗粒更新, 颗粒团, 床层-壁面, 气泡

Abstract:

Based on the previous experimental study, a computational particle fluid dynamics (CPFD) model was used to reveal the heat transfer mechanism between a vertical heat tube and a fluidized bed of fine FCC particles. Emphasis was put on the hydrodynamics related to the particle renewal on the heat tube surface. The relationships between the gas-solids hydrodynamics on the heat tube surface and the local heat transfer properties were discussed. The predicted total particle renewal fluxes and packet mean residence time according to the packet renewal model at different superficial gas velocities and radial positions can both explain the change of the measured heat transfer coefficients, which indicates the dominant role of the particle renewal on the bed-to-wall heat transfer in a bubbling fluidized bed. As the heat tube moves from the bed center to the column wall, there is an increasing tendency for the circumferential non-uniformities of both solids renewal flux and heat transfer coefficient. As the superficial gas velocity increases, the internal solids circulation flux in the bed increases as a result of stronger bubble movement, which is the root cause of the strengthened solids renewal on the heat tube surface and the increased heat transfer coefficient.

Key words: computational particle fluid dynamics, fluidized bed, heat transfer, solids renewal, packet, bed-to-wall, bubble