颗粒无序分布的堆积床内部流动与传热分析

Analysis of Internal Flow and Heat Transfer in Packed Bed with Particles Random Distribution

关键词:  堆积床  流动  传热  离散单元法  网格生成  数值模拟

Key words:  Packed bed  Flow  Heat transfer  Discrete element method  Mesh generation  Numerical simulation

摘要:

为了详细分析单组元发动机催化床内部的流动与传热，针对颗粒无序分布的堆积床，提出了一种网格生成途径，适合于对大量颗粒自然堆积的管道流动进行数值模拟。根据该方法，对不同颗粒直径、不同进口速度的管道堆积床进行了液体介质的流动与非定常传热模拟，并与实验结果和Ergun方程计算进行了对比。结果表明，本文提出的方法可以有效模拟颗粒无序分布的堆积床内部流动与传热，适合于大量颗粒的堆积床仿真；网格尺度小于1/20颗粒直径时，模拟结果与实验结果符合很好；在相同雷诺数下，摩擦系数随颗粒直径增大而减小，Ergun方程在高雷诺数下计算的流阻偏大；非定常传热时，壁面效应会使壁面附近温度先接近流体温度。

Abstract:

In order to analyze the flow and heat transfer inside the catalytic bed of monopropellant rocket thruster in detail， a mesh generation method was proposed for the random distribution of particles in packed bed， which is suitable for the numerical simulation of pipe flow with a large number of particles naturally packed. Based on this method， the flow and unsteady heat transfer of liquid medium in the packed bed were simulated by changing diameter of the particle and inlet velocity of the pipe， and compared with the experimental results and the Ergun equation results. The results show that the proposed method can effectively simulate fluid flow and heat transfer within the packed bed where particles randomly packed and is suitable for simulation of packed bed with a large number of particles. The simulation results agree well with the experimental results when the grid scale is less than 1/20 particles diameter. Under the same Reynolds number， the friction coefficient decreases with the increase of particle diameter， and the flow resistance calculated by Ergun equation at high Reynolds number is larger than the simulation. In unsteady heat transfer process， near wall temperature approaches to fluid temperature firstly because of wall effect.