大颗粒流化床传热数值模拟与气固传热模型比较

采用欧拉-欧拉模型对GeldartD类颗粒气固流化床的非定常传热过程进行了模拟,比较了包括Gunn模型在内的6种不同的气固传热系数模型.通过模拟二维流化床发现,基于6种气固传热模型得出的平均壁面传热系数与文献的实验关联式相差不大,但是6种模型给出的局部气固传热系数呈现较大的差别,其原因在于不同模型中的两个主要影响参数颗粒雷诺数和床层空隙率的贡献不同.比较了6种气固传热模型之后,采用Gunn模型对D类颗粒的流化床进行了模拟和分析,结果表明:尽管存在较大的气泡和一定程度的腾涌,D类颗粒流化床可以实现稳定的流化.从流化床内的温度分布的演化来看,D类颗粒流化床的传热均匀性不存在问题,较大的颗粒直径和较大的气泡并未造成传热问题.

Numerical Simulation of Large Particle Fluidized Bed and Comparison of Gas particle Heat Transfer Models

Unsteady heat transfer in a gas-solid fluidized bed of Geldart D particles was simulated with the help of Eulerian-Eulerian fluid dynamic method.6 gas-particle heat transfer coefficient models were compared and analyzed.According to the simulation of a two-dimensional bed,it is found that the mean wall heat transfer coefficient of the whole bed is in good agreement with that based on the reported experimental correlative expression.However,the gas-particle heat transfer coefficient based on local conditions in the bed is found to be varied obviously when different models are used.A thorough numerical simulation was conducted with Gunn model to investigate the two-phase flow and heat transfer in the Geldart D particle bed.Relatively stable fluidization can be observed,although more or less bubbling exists.Uniform temperature distribution is easily reached when fluidization initialization has finished.