Experimental study of exit effect on gas-solid flow and heat transfer inside CFB risers
Experimental study of exit effect on gas-solid flow and heat transfer inside CFB risers
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DOI：
10.1016/j.expthermflusci.2013.08.011
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发表时间：
2013-11
影响因子：
3.2
通讯作者：
Ruiqing Zhang;Hairui Yang;Yuxin Wu;Hai Zhang;Junfu Lu
中科院分区：
文献类型：
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作者：
Ruiqing Zhang;Hairui Yang;Yuxin Wu;Hai Zhang;Junfu Lu
在两台尺寸相似但截面形状不同的冷态循环流化床（CFB）实验台上，研究了不同出口几何形状对气固流动和传热特性的影响。在一定的表观气速和固体循环流量下，固体密度和床-探针传热系数沿提升管沿着的轴向分布具有良好的相关性。急出口会使出口附近甚至整个提升管内的固体浓度和传热系数增大。由于空腔和碰撞效应的共同作用，固体浓度将首先随着突出口投影高度的增加而增加。当突出口高度超过颗粒所能达到的最大高度时，颗粒浓度将保持不变甚至下降。除了出口形式和操作条件外，突出口的突出口高度、截面尺寸和形状都是影响出口效果的重要因素。在本文中，出口效应变得更显着的圆形截面比矩形的。
In two bench-scale cold circulating fluidized bed (CFB) risers with similar dimension but different cross section shape, the effect of different exit geometries on both gas–solid flow and heat transfer characteristics was investigated. The measured axial distribution of solid density and bed-to-probe heat transfer coefficient along the riser were found to have good correlation at certain superficial gas velocity and solid circulating flux. Abrupt exit can bring higher solid concentration and heat transfer coefficient near the exit, even in the whole riser. Due to combining effort of cavity and collision effect, solid concentration will first increase with projected height of the abrupt exit increasing. Then solid concentration will stay constant or even decrease when projected height increases over the maximum height particles can reach.Besides exit types and operating conditions, projected height of the abrupt exit, size and shape of cross section are all important factors affecting exit effect. In this paper, exit effect becomes more significant with a circular cross section than a rectangular one.