移轉速度的存在性及其對紊流流化床 流態行為之研究

The Study of the Existence of Transition Velocity and the Hydrodynamics of Turbulent Fluidized Beds

蕭明昌(Ming-chang Shou)

指導教授 ： 呂理平

國立臺灣大學/工學院/化學工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.02356

摘要

摘要

關於氣-固流體化床由氣泡床到快速床間之流態轉變，以及紊流床是否存在之問題，至今尚無定論。根據Rhodes (1996)對文獻上各研究者所得之結果分析比較，發現目前有關流態之轉變及移轉速度之探討，仍莫衷一是。因此吾人提出利用結合反射型光纖探針、熱傳探針、壓力探針來探討氣固流體化床在流態改變時床中空隙度、床-壁間傳熱係數、壓力擾動振幅三者的變化及其相關性，以了解床中之變化及其對流態之影響，並試圖證明移轉速度之存在。

本實驗裝置為內徑0.108m、高5.7m，頂端接有高1.5m擴大管的流體化床及其他形式之床體，使用數種不同粒徑Group A及Group B粒子為研究對象，分別以反射型光纖探針量測床中粒子局部空隙度及其軸向變化；以熱傳探針量測床-壁間傳熱係數及其軸向變化；以壓力探針量測床中擾動振幅大小及其軸向變化，藉由不同型式探針量測之結果，及不同統計方式之分析比較，以作為判斷移轉速度存在之指標，並了解紊流流體化床之動力行為。

關鍵字

壓力探針 ； 光纖探針 ； 小波 ； 移轉速度 ； 熱傳探針

並列摘要

Abstract

The transition from bubbling bed to fast fluidization bed will be investigated by using (1) optical fiber to measure the local bed voidage distribution, (2) pressure probe to measure the pressure fluctuations and (3) heat transfer probe to measure the bed-to-wall heat transfer coefficient. This transition region from bubbling bed to fast fluidized bed is now widely referred to the turbulent fluidized bed, the structure of this bed and the mechanism for the transition are still unclear.

Experimental study will be carried out in a 0.108 m i.d., 5.76m high with expanded-top fluidized bed, and other type of bed. Several different sizes of Group A and B particles will be used as the fluidized particles. The local bed voidage will be measured by reflection type optical fiber probe. With the addition of mean amplitude of pressure fluctuations and bed-to-wall heat transfer coefficient measurements, hopefully the transition mechanism and the bed structure could be understood in more detailed way, and the existence of “turbulent fluidized bed” could be explained in a logical sense. Above all, by wavelet analysis, the existence of transition velocity could be identified and the hydrodynamics of turbulent fluidized bed could be characterized.

並列關鍵字

optical fiber ； transition velocity ； pressure probe ； heater probe ； wavelet

參考文獻

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