Research On Radiation Characteristics Of Particles In Gas-solid Two-phase System

The gas-solid two-phase in fluid-bed flow and its heat transfer problem are currently hot issues.Fluidized beds are widely used in engineering and have applications ranging from large fluidized bed boilers to micro fluidized beds for gas-solid catalytic reactors.This paper is based on the Computational Fluid Dynamics-Discrete Element Method(CFD-DEM)under the Euler-Lagrange method,using the DDPM(Dense Discrete Phase Model)model and the DEM(Discrete Element Method)model.The particle distribution in the fluidized bed was numerically simulated and based on it,the radiation characteristics of the fluidized bed particle system were analyzed.The particle systems with different spatial regions were selected,and the radiation characteristics of the particle system were analyzed using the multi-sphere T-matrix method,and analyzed and compared with the radiation characteristics of the particle systems with independent scattering.In this paper,Euler's method is used to simulate the gas phase in the fluidized bed two-phase flow.For solid particles,the DDPM-DEM model is used.The DDPM-DEM model considers the interaction between particles and particles,particles and walls,and particles and the continuous phase,and is suitable for higher particle phase volume fractions compared to the traditional discrete phase model.The model was established on a fluidized bed with an internal diameter of 0.1 mm.The particle sizes of the particles were 3.6 ?m,4.5 ?m,and 6 ?m,respectively.The volume fractions of solid particles were 8.91%,11.88%,14.88%,and 17.86%,respectively.The characteristics of the flow field and the spatial distribution of the particle phase in the fluidized bed were analyzed.The results show that with the same fluidization velocity,particles in the fluidized bed are more difficult to fluidize with the increase of the particle size of the solid phase,and the influence of the particle size on the particle size is greater than that of the solid phase particle..Based on the numerical simulation of the fluidized bed flow field,the spatial distribution of the particle system is obtained.The multi-sphere T-matrix method that takes into account the coherence of the electromagnetic waves between the particles is used to analyze the radiation characteristics of the particle system,and the results are calculated with the independent scattering.analyse and compare.It was found that the scattering factor gradually decreased with the increase of the volume fraction of the particle system at the same particle size;the radiation characteristics of the particle system calculated using the multi-sphere T-matrix differed greatly from the results of the independent scattering,and followed.With the decrease of the volume fraction of the particle system,the difference between the two decreases gradually.When the particle system volume fraction is less than 8%,the scattering of the particle system starts from the non-independent scattering to the independent scattering.