Comparative study of Transport Disengaging Height (TDH) correlations in gas–solid fluidization
Comparative study of Transport Disengaging Height (TDH) correlations in gas–solid fluidization
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气固流化中传输脱离高度（TDH）相关性的比较研究
DOI：
10.1016/j.powtec.2015.02.010
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发表时间：
2015
影响因子：
5.2
通讯作者：
J. Chew
中科院分区：
文献类型：
--
作者：
Andy Cahyadi;Anthony H. Neumayer;C. Hrenya;R. Cocco;J. Chew
输送分离高度(TDH)是气固流态化系统设计中的一个重要参数，它定义为使夹带率不发生明显变化的超高高度[1-6]。不幸的是，尽管自1958年开始并随后发展了TdH关联[4]，但由于缺乏对TdH现象的基本理解而依赖于经验数据拟合，预测值和实验值之间的一致性很差[1]。因此，这项工作旨在提供一个全面的回顾现有的TDH值关联式。由25个关联式预测的TDH值在一系列的表观气速、颗粒大小、颗粒大小分布和柱径范围内被评估。有四个观察结果值得强调：(I)在由各种关联式预测的TDH值之间发现高达五个数量级的差异，(Ii)预测的非物理现象包括负的TDH值，(Iii)对于Geldart B组颗粒，Geldart B组关联比Geldart A组颗粒关联执行得更好，以及(Iv)在从自由鼓泡到段塞流的转变中预测经常失败。使用经验常数来改进经验数据拟合，以产生经验的TDH值关联，对于改进TDH值的预测或促进对TDH值现象的理解都是无用的。根据经验得出的关联性在测试的狭窄实验条件范围之外表现不佳，而可用的半经验或理论模型也达不到要求。由于缺乏对颗粒间相互作用(例如，凝聚力或聚集效应)和物种间相互作用(例如，碰撞动量转移效应)的影响的了解，现有的tdh相关性缺乏预测能力。
Transport Disengaging Height (TDH), defined as the freeboard height whereby the entrainment rate does not change appreciably [1–6], is an important parameter in the design of gas–solid fluidized bed systems to minimize particle loss. Unfortunately, despite the initiation and subsequent development of TDH correlations since 1958 [4], poor agreement between predicted and experimental values persists [1] due to the reliance on empirical data-fitting in the absence of a fundamental understanding of the TDH phenomenon. Accordingly, this work aims to provide a comprehensive review of the available TDH correlations.TDH values predicted by 25 correlations were evaluated over a range of superficial gas velocities, particle sizes, particle size distributions, and column diameters. Four observations are worth highlighting: (i) Discrepancies of up to five orders of magnitude were found among TDH values predicted by the various correlations, (ii) Unphysical phenomena predicted include negative TDH values, (iii) Geldart Group B correlations perform better for Geldart Group B particles than Geldart Group A correlations for Geldart Group A particles, and (iv) Prediction often fails in the transition from the freely bubbling to the slugging regime.The ad hoc inclusion and/or exclusion of parameters, and the use of empirical constants to improve empirical data-fitting in the generation of empirical TDH correlations are not useful in either improving predictions of TDH values or advancing the understanding of the TDH phenomenon. Correlations empirically derived do not perform well beyond the narrow scope of experimental condition tested, while semi-empirical or theoretical models available fall short. The lack of predictive capability of the available TDH correlations appears to stem from a deficiency in an understanding of the impact of inter-particle (e.g., cohesion or clustering effects) and inter-species interactions (e.g., collisional momentum transfer effects).