柱形流化床传热特性的数值模拟

doi:10.12034/j.issn.1009-606X.218119

摘要/Abstract

摘要： 对Shedid等搭建的圆柱体流化床采用欧拉?欧拉法进行三维数值模拟，考察了颗粒球形度、表观进气速度和床料初始堆积高度对流化床内垂直加热壁面与流动床料之间对流传热特性的影响，采用有效导热系数分别计算气相和固相的对流传热系数。结果表明，随表观进气速度增大，流化床内颗粒物料湍流运动加剧，加热壁面平均温度和流体平均温度下降，壁面流体间传热平均温度差减小，壁面流体间对流传热系数增大；随初始床料高度增加，流化床内颗粒与加热壁面的接触面积增大，导致固相平均对流传热系数增大。

关键词: 流化床, 双流体模型, 温度特性, 两相流, 对流传热系数

Abstract: Based on the cylinder fluidized bed built by Shedid and Hassanto, a three-dimensional Euler–Euler simulation of the effect on the convective heat transfer characteristics between the fluidized particles and the inner heated surface was carried out under different operation conditions including particles sphericity, superficial gas velocity and initial solid packing height in the vertical fluidized bed. Moreover, the experimental average temperature had been chosen to test the validity of numerical average temperature. Contour plots of transient distribution of solid volume fraction and solid temperature have been obtained in fluidized bed on horizontal cross-section in order to understand the effects of hydrodynamic and flow patterns on heat transfer characteristics. The results showed that the solid phase concentration distributed from the initial centrally symmetric annular stratification to the final severely turbulent fluidization by observing contour plots of the solid-phase volume fraction on horizontal cross-section. Solid temperature decreased from center to periphery in the radial direction at initial state since the gas–solid heat exchange rate affected the particle temperature in the entire bed. The temperature distribution of particles was non-uniform on the annular region due to the bed without being fluidized. With the process of fluidization underway, the particles temperature distribution tended to be uniform in horizontal cross-section because the bed material heat transferred from the center's cylindrical heater wall to the bed. The effective thermal conductivity was used to calculate the individual gas and solid phase convective heat transfer coefficient from heater surface to fluidized beds. Not only the average temperature of both heating wall and fluid but the difference of the average temperature between wall and fluid were decreasing with increasing superficial gas velocity. It enhanced turbulence intensity and led to increase the heat transfer coefficient between heater surface and fluid with the same time. The solid average convective heat transfer coefficient growed up with the initial height increasing of the bed material due to the contact area enlargement of particles and the heated surface in the fluidized bed.

Key words: fluidized bed, two-fluid model, temperature characteristic, two-phase flow, convective heat transfer coefficient

王力军段叔平徐凌锋孙嘉君. 柱形流化床传热特性的数值模拟[J]. 过程工程学报, 2019, 19(1): 110-117.

Lijun WANG Shuping DUAN Lingfeng XU Jiajun SUN. Numerical simulation on heat transfer in a cylindrical fluidized bed[J]. Chin. J. Process Eng., 2019, 19(1): 110-117.

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