CIESC Journal ›› 2016, Vol. 67 ›› Issue (5): 1732-1740.DOI: 10.11949/j.issn.0438-1157.20151335

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CPFD simulation on heat transfer mechanism of vertical tube in bubbling fluidized bed

WEI Qing, YAO Xiuying, ZHANG Yongmin   

  1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China
  • Received:2015-08-24 Revised:2016-01-08 Online:2016-05-05 Published:2016-05-05
  • Supported by:

    supported by the National Natural Science Foundation of China (21276273), the National Basic Research Program of China (2012CB215004), the Program for Yong Excellent Talents in Universities organized by the Beijing Government (YETP0675) and the Science Foundation of China University of Petroleum, Beijing (2462015YQ0312).

竖直管气固鼓泡流化床传热机理的CPFD模拟

魏庆, 姚秀颖, 张永民   

  1. 中国石油大学(北京)重质油国家重点实验室, 北京 102249
  • 通讯作者: 张永民
  • 基金资助:

    国家自然科学基金项目(21276273);国家重点基础研究发展计划项目子课题(2012CB215004);北京高等学校青年英才计划人才专项基金项目(YETP0675);中国石油大学(北京)科研基金项目(2462015YQ0312)。

Abstract:

Based on the previous experimental study, a computational particle fluid dynamics (CPFD) model was used to reveal the heat transfer mechanism between a vertical heat tube and a fluidized bed of fine FCC particles. Emphasis was put on the hydrodynamics related to the particle renewal on the heat tube surface. The relationships between the gas-solids hydrodynamics on the heat tube surface and the local heat transfer properties were discussed. The predicted total particle renewal fluxes and packet mean residence time according to the packet renewal model at different superficial gas velocities and radial positions can both explain the change of the measured heat transfer coefficients, which indicates the dominant role of the particle renewal on the bed-to-wall heat transfer in a bubbling fluidized bed. As the heat tube moves from the bed center to the column wall, there is an increasing tendency for the circumferential non-uniformities of both solids renewal flux and heat transfer coefficient. As the superficial gas velocity increases, the internal solids circulation flux in the bed increases as a result of stronger bubble movement, which is the root cause of the strengthened solids renewal on the heat tube surface and the increased heat transfer coefficient.

Key words: computational particle fluid dynamics, fluidized bed, heat transfer, solids renewal, packet, bed-to-wall, bubble

摘要:

针对细颗粒气固鼓泡流化床中床料与竖直传热管壁面间的传热行为,在前期实验的基础上,采用计算颗粒流体力学(CPFD)方法从颗粒在传热壁面更新的角度,深入分析了传热特性与壁面气固流动行为之间的关联性。结果表明,模拟得到的传热管壁面颗粒更新通量和基于颗粒团更新模型的颗粒团平均停留时间均能很好解释实验测得的传热系数变化规律,这证实颗粒团更新是影响传热过程的控制性因素。模拟还发现随加热管从床层中心向边壁的移动,加热管周向方向上颗粒更新通量和传热系数的不均匀性都呈增大趋势。随着表观气速的增大,气泡行为导致床层颗粒内循环流率增大,这是导致颗粒团在加热管壁面上的更新频率增大以及床层与壁面间传热系数增大的根源。

关键词: 计算颗粒流体力学, 流化床, 传热, 颗粒更新, 颗粒团, 床层-壁面, 气泡

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