三维填充床内换热及热回流机理研究

Study on heat transfer and heat reflux mechanism in high temperature packed bed

利用计算流体力学(CFD)对顺序排列多孔介质小球的三维填充床进行数值模拟。研究填充床内位置及空气流速变化对温度分布、努塞尔数影响,并对多孔介质小球的热回流特性进行分析,揭示填充床内传热机理。结果表明:相比于气-固两相交替存在处,与小球相切处的热的非平衡性更强。最高温度上游的换热强度与下游相比更强烈;当流速增加时,上游的对流换热作用增强,下游变化不大。在热回流过程中,入口区域对流换热占主导地位,导热和辐射换热作用较弱;在主流场区域,导热占主导地位,对流换热作用最弱。

Computational fluid dynamics(CFD)was used to numerically study the influence of different positions and air velocity on temperature distribution and Nusselt number,and analyze the heat reflux characteristics of orderly arrangement porous medium sphere arranged in a 3D packed bed.The results show that compared with that at the gas-solid alternate position,the thermal non-equilibrium at the tangent to the pellets is stronger.The heat transfer intensity at the upstream of the highest temperature is stronger than that at the downstream;when the flow velocity increases,the heat transfer at the upstream increases,and the downstream changes little.In the heat reflux process,convection heat transfer is dominant in the entrance area,and the effects of heat conduction and radiation heat transfer are weak;in the mainstream field area,heat conduction is dominant,and convection has the weakest effect.