Surface‐to‐suspension heat transfer model in lean gas–solid freeboard flow
作者:
Ihab H. Farag,
Kun‐Yung Tsai,
期刊:
The Canadian Journal of Chemical Engineering
(WILEY Available online 1993)
卷期:
Volume 71,
issue 4
页码: 514-524
ISSN:0008-4034
年代: 1993
DOI:10.1002/cjce.5450710403
出版商: Wiley Subscription Services, Inc., A Wiley Company
关键词: fluidization;heat transfer;freeboard;mechanistic models
数据来源: WILEY
摘要:
AbstractHeat transfer in dense fluidized beds have been extensively studied. However, there is not much detailed information about the mechanism of surface‐to‐suspension heat transfer in the freeboard region. In the present work, a newly designed heating plate was used to measure the plate‐surface‐to‐particle‐suspension heat transfer coefficients in the freeboard.The experimental unit consisted of a 30 cm i.d. fluidized bed reactor packed with fluidized catalytic particles of mean particle size 90 μm. Three types of plate orientations were used to test directional effects of surface on heat transfer rate. Height of the freeboard was 171 cm, and the superficial gas velocity was varied from 0.28 to 0.64 m/s. Local solids concentrations in the freeboard were also obtained by a nozzle‐type sampling probe. Data on axial distribution of solids concentration were used to find out the solids kinematics in the freeboard region. Finally, a surface‐to‐suspension heat transfer model was developed to elucidate the surface to particle heat transfer mechanism in this lean phase system.The model is based on the transient gas‐convective heating of single particles when sliding over the heating plate and the assumption of instantaneous attachment–detachment equilibrium between particles
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