超临界水流化床床床层与壁面间传热特性研究

Bed to Wall Heat Transfer in Supercritical Water Fluidized Bed

本文基于颗粒动理学理论建立了流化床中的欧拉双流体模型,采用了单气泡沿壁面运动物理模型,从颗粒分布特性、温度分布特性和瞬时传热特性三个方面对超临界水流化床和气固流化床的床层与壁面间传热特性进行了对比研究。研究表明,相同条件下,相对于气固流化床,超临界水流化床中气泡的直径和上升速度都较小;超临界水流化床中床层与壁面间的传热系数与颗粒浓度呈反相关关系,而对于气固流化床则是正相关关系;并且不同于气固流化床,超临界水流化床床层与壁面间传热系数在颗粒浓度较低处对表观速度变化比较敏感。

The Eulerian two-fluid model based on Kinetic Theory of Granular Flow in a nuidized bed was established in this paper,and the physical model of movement of single bubble along the wall is adopted.The comparison studies of particle distribution,temperature distribution and transient heat transfer characteristics between supercritical water(SCW) nuidized bed and gas-solid fluidized bed were carried out.The results show that the bubble diameter and rise velocity in SCW fluidized bed is smaller than those in gas-solid fluidized bed.The bed-wall heat transfer coefficient is negative related to solid volume fraction in SCW fluidized bed,while positive in gas-solid fluidized bed.What is more,the bed-wall heat transfer coefficient is sensitive to superficial velocity where the solid volume fraction is low,which is different from gas-solid fluidized bed.