摘要
为了了解内置有传热管列而被强化的固定床床层内的错流流动,在考虑对流项和扩散项对流场的作用情况下,基于Ergun方程建立了该种固定床反应器多孔介质的数学模型,模拟了床层的压力分布,然后在管子按不同的三角形和正方形排列方式情况下,研究了床层内气体在多圆管管间及周边的速度分布。由于管道的阻挡,沿主体流动方向的速度分量v在圆管正前、后方近壁处,v显著下降,随着离开圆管距离的增大,其影响减弱,影响范围≤1.0Dt;气体在圆管前后流速下降,管间流速呈现增大的波形曲线,其波峰和波幅的大小以及波形曲线的形状,不仅与管间距离和入口速度有关,而且与圆管的排列方式有关。计算结果与实验值比较表明模型能正确描述床层的压力分布;采用三角形排列方式,与采用正方形排列方式相比,强化了床层内的对流传热,使得床层内温度分布更趋于均匀。
Based on the Ergun＇s equation and with considering the convection term and diffusion term of the fluid flow, a mathematic model used to simulate the fluid flow in the fixed-bed reactor with inner immersed tubes was established. Using the model developed, the pressure distribution of the fixed-bed reactor was calculated, and the calculating results have good agreement with the corresponding experimental data obtained from literature, which indicates that the model is reliable. Furthermore, the model was used to study the gas velocity distribution affected by the immersed tubes in the fixed-bed reactor. The results show that along the main gas flow direction, the gas velocity v close to the tube-wall descends remarkably at the front of and behind the tubes because of the hindrance of the tubes, however, the v increases between the tubes. The peak and width of the wavy gas velocity distribution curves along the width of the fixed-bed are relative to the space between the tubes, the inlet gas velocity and the tube arrangement mode. It is found that the hindrance effect of the tube on the gas velocity is only limited within a distance of the tube diameter measured from the center of the tube. It is also shown that the staggered arrangement of the tubes with triangular pitch will cause stronger disturbance of the gas flow than that caused by the in-line arrangement with square pitch, so that the former arrangement mode will favor to the heat transfer and will cause the temperature field to become more uniform in the fixed-bed reactor.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2006年第4期527-532,共6页
Journal of Chemical Engineering of Chinese Universities
