Analysis Of Flow Mixing And Compound Heat Transfer Characteristics In Circulating Fluidized Bed

Internal circulating fluidized bed has a wide range of applications in combustion,gasification and pyrolysis,which makes the flow and heat transfer process of dense gas-solid two-phase flow become an important direction in the field of multiphase flow.In order to improve the combustion efficiency of fluidized bed equipment,it is necessary to have a deeper understanding of the flow and heat transfer mechanism of particles in fluidized bed.In this paper,experiments and numerical simulations of the flow mixing and heat transfer characteristics of particles in a fluidized bed are carried out mainly through the Euler-Euler model.In this paper,the numerical simulation of heat transfer characteristics of annular fluidized bed built by Shedid et al is carried out,and the accuracy of mathematical modeling is verified by comparing with the experimental results.The radiation heat transfer in fluidized bed is studied by using discrete coordinate model,and the user-defined function is compiled to study the effect of particle emissivity on radiation heat transfer,and the radiation heat transfer characteristics are studied by gray model and non-gray model,respectively.Then,the internal circulating fluidized bed established in the laboratory was used to simulate the flow mixing and heat transfer of the fluidized bed under simulated conditions using the Euler-Euler model.Gidaspow model is used to describe the interaction between gas and solid and non-gray model is used to simulate radiation heat transfer.The results show that with the increase of heating heat flux,the temperature of fluid and heating tube and the heat transfer coefficient between particles and heating tube also increase.In addition,under high heat flux conditions,the radiation heat transfer coefficient can reach about 40% of the total heat transfer coefficient.Under different initial solid packing height,the variation trend of fluid temperature and heater surface temperature is opposite.The convection heat transfer coefficient and total heat transfer coefficient increase with the increase of initial solid packing height.In the process of increasing intake volume flow,both fluid temperature and heating tube surface temperature show a decreasing trend,and the radiation heat transfer coefficient shows a decreasing trend.The results obtained by experiments and numerical simulations are in good agreement and the law of change is the same.The numerical simulation of the mixing and heat transfer process of the particles in the circulating fluidized bed provides the practical reference value for the design and operation of the fluidized bed.