循环流化床颗粒团更新传热模型的修正

Modification to The CFB Cluster-Renewal Heat Transfer Model

对颗粒团更新传热模型进行了修正 ,引入新的床内流动特性的研究结果 ,改进了颗粒团覆盖壁面的百分比和颗粒团 -壁面之间的气膜厚度的表达式 ,使之与床的宏观运行参数以及床体、床料的参数相联系 ,从而避免了前人模型中凭经验来确定一个比例系数的缺陷。对于弥散相和壁面间的辐射传热 ,考虑到了它们的直接辐射和弥散相辐射到颗粒团、再经颗粒团反射到壁面的传递过程。模型计算结果和有关实验数据的对比吻合较好。图 4表 1参 1

Based on the Cluster renewal Model of the particle motion in a CFB riser, the authors developed a revised heat transfer model, which introduced the latest research results of the hydrodynamics of the suspension flow in CFB. This model divided the heat transfer into two parts, which are due to the transient heat conduction by the covered clusters and the convection between the uncovered wall and the dispersed phase. Radiation at high temperature was regarded as being additive. The fraction of the covered wall by clusters and the thichness of the gas gap between clusters and wall were revised by a new formula, which is a function of the operating condition and the particle properties. The radiation between the dispersed phase and the uncovered wall included not only the direct radiation to the uncovered wall, but also the radiation to the clusters and then reflected to the uncovered wall. The model results showed good agreement with the published experimental data, which proved the modification was reasonable. Figs 4, table 1 and refs 10.