• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Hydrodynamics and heat transfer in the solid recycle system of circulating fluidized beds.
【24h】

Hydrodynamics and heat transfer in the solid recycle system of circulating fluidized beds.

机译：循环流化床固体循环系统中的流体动力学和传热。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

This research covers two aspects of the circulating fluidized bed (CFB) solid recycle system: the hydrodynamics of solid flow through the loop seal and the heat transfer in the moving packed bed of the standpipe.; The flow of solids through the horizontal passage of the loop seal of a CFB was studied. The effect of the length of an un-aerated horizontal passage on the solid flow through the loop seal was examined. It was found that as the passage length increases, the resistance to solid flow through the passage increases as a result of increased frictional resistance and increased area of stationary solids at the end of the passage. The flow of gas from the supply chamber was found to be the driving force for solid flow through the loop seal as the majority of the supply chamber aeration flows horizontally through the passage to the recycle chamber and not upwards through into the standpipe. The flow of solids through the loop seal was found to begin only after a threshold of gas velocity was reached and increased with increasing aeration, to a maximum solid flow, beyond which further increases in loop seal aeration had no effect on the solid flow through the loop seal. This maximum was limited by factors such as passage length, riser aeration, solid inventory and particle properties.; To understand the solid flow through the horizontal passage better the mobility of the bed particles was studied. The 'spread angle' of an aerated heap of solids (angle the heap makes with the horizontal) of varying sizes and sphericities, was investigated. It was found that particles with a higher sphericity had a smaller spread angle and thus are more mobile than less spherical particles. The size of the particle had little effect on the initial spread angle of the heap, with a larger particle requiring a higher aeration velocity to reach the same spread angle as a smaller particle. The spread angle is zero at an aeration velocity equal to the minimum fluidization velocity for all particle shapes and sizes.; The heat transfer to cross tubes in a moving packed bed was studied to determine the heat transfer characteristics of solid flow in the standpipe of the CFB solid recycle system. The effect of tube diameter on heat transfer was studied. It was found that the heat transfer coefficient between the moving packed bed and the tube decreased with increasing tube diameter, due to the increased residence time of the particles on the tube. It was also confirmed that an increase in particle diameter caused a decrease in heat transfer due to an increase in the gas-gap annulus that exists adjacent to the tube surface. The empirical relation for heat transfer to a cross-flow tube in a moving packed bed developed by Obuskovic et al. (1991) was modified to fit the current experimental data. The model showed a good correlation for the present data as well as for that reported by Courbariaux et al. (1999).
机译：这项研究涵盖了循环流化床（CFB）固体循环系统的两个方面：通过环路密封的固体流动的流体动力学和立管移动式填充床中的热传递。研究了通过CFB环形密封件水平通道的固体流。检查了未充气水平通道的长度对通过环封的固体流的影响。已经发现，随着通道长度的增加，由于增加的摩擦阻力和通道末端固定固体面积的增加，对通过通道的固体流动的阻力也随之增加。发现来自供应室的气流是固体通过回路密封的驱动力，因为大部分供应室的曝气水平通过通道流向再循环室，而不是向上进入竖管。发现只有在达到气体速度阈值之后，固体才开始通过环路密封件流动，并随着充气的增加而增加，直到达到最大固体流量，超过此值，环路密封件充气的进一步增加对通过管道的固体流量没有影响。循环密封。该最大值受诸如通道长度，立管充气，固体物料和颗粒性质等因素的限制。为了更好地了解通过水平通道的固体流，研究了床颗粒的迁移率。研究了不同大小和球形度的充气的固体堆的“散布角”（堆与水平方向所成的角度）。已经发现，具有较高球形度的颗粒具有较小的扩展角，因此比较少球形的颗粒具有更高的运动性。颗粒的尺寸对堆的初始铺展角几乎没有影响，较大的颗粒需要较高的通气速度才能达到与较小的颗粒相同的铺展角。对于所有形状和尺寸的颗粒，在曝气速度等于最小流化速度时的扩散角为零。为了确定CFB固体循环系统竖管中固体流的传热特性，对在移动填充床中横管的传热进行了研究。研究了管径对传热的影响。已经发现，由于颗粒在管上的停留时间增加，所以移动的填充床与管之间的传热系数随着管直径的增加而减小。还可以确认，粒径的增加是由于存在于管表面附近的气隙环的增加而引起的热传递的减少。 Obuskovic等人开发的将热量传递到移动填充床中的横流管的经验关系式。 （1991）被修改以适应当前的实验数据。该模型与当前数据以及由库尔巴里亚等报道的数据显示出良好的相关性。 （1999）。

著录项

  • 作者

    Butler, James.;

  • 作者单位

    Dalhousie University (Canada).;

  • 授予单位 Dalhousie University (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 M.A.Sc.
  • 年度 2007
  • 页码 124 p.
  • 总页数 124
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号