循环流化床稀相区对流换热的理论分析和实验研究

Theoretical Analysis and Experimental Research of Convective Heat Transfer of Circulating Fluidized Bed Boilers in the Upper Dilute Zone

对循环流化床上部稀相区气固混合物横掠圆管的对流换热研究,多数是针对鼓泡床的研究,而对循环流化床上部稀相区的对流换热研究目前还很少。本文对稀相含尘气流横向冲刷圆管的对流换热进行了研究,并在理论分析的基础上,在热态循环流化床实验台的上部稀相区进行了实验。采用平均粒径分别为137μm,146μm和326μm的石英砂为床料。实验结果表明,稀相含尘气流与纯空气横掠圆管时的对流换热系数之比hd/hg主要受稀相含尘气流密度和颗粒粒径的影响,通过理论分析和实验数据的拟合,得到稀相含尘气流横掠圆管的准则方程。研究基于热态实验,结果更接近于实际工况,可为循环流化床的设计提供理论依据。

The convective heat transfer of dilute gas - solid two phase flow across the circular tubes is researched in this paper. Based on the theoretical analysis, the experimental research is carried out in the dilute gas - solid mixture. Three kinds of quartz sands, whose average diameters are 137μm, 146μm and 326μm respectively, are used as fluidizing particles. The experimental results show that the ratio of convective heat transfer coefficients between dilute gas - solid two phase flow and the air flow which crosses the circular tubes is mainly affected by the density of dilute gas - solid mixture and the average diameter of fluidizing particles. By means of handling experimental data , the criterion equation used to dilute gas - solid two phase flow across circular tubes is obtained. The experimental condition is similar to pratical condition, so the results, as mentioned above , can be used as basis to design circulating fluidized bed.