Simulation of cylindrical fluidized bed between granular flow and annulus surface

Abstract

In this paper, a three dimensional Eulerian–Eulerian simulation, for the vertical heater wall to bed heat transfer in a cylindrical fluidized bed, was conducted numerically with the results compared to the experimental ones. In this process, the understanding of the heat transfer mechanism of gas-solid flow in the fluidized bed is deepened, which provides a reference for the design and operation of practical fluidized bed burner equipment. Gidaspow's drag correlation was adopted to describe the interaction between the gas and the solid phases in the fluidized bed. Moreover, a user-defined function (UDF) of the gas-solid inter-phase exchange coefficient was derived obtain the temperature and heat transfer characteristics in the fluid area, with different particle shapes. Temperature and heat transfer coefficient were numerically analyzed under different operating conditions that are consistent with the experimental setups. The effects of initial solid packing height onto the heat transfer characteristic, together with the average total and convective heat transfer coefficient, were investigated, where the average temperature was compared with the experimental data in the literature. The simulation results showed that the average temperature and heat transfer coefficient well agree with the experimental data, and the average heat transfer coefficient is increased by about 60% with the increasing initial solid packing height. Therefore, it is essential to obtain the distribution of temperature in annular horizontal cross-section as well as solid flow characteristics with the varying time for comprehensive understanding of the heat transfer process. The instantaneous variations between the local heat transfer coefficient and the solid volume fraction were analyzed under different gas inlet velocity.