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研究生:徐維隆
研究生(外文):Wei-Long Hsu
論文名稱:內循環式流體化床環形區床-壁間熱傳性質
論文名稱(外文):Annulus Bed-to-Wall Heat Transfer in an Internally Circulation Fluidized Bed
指導教授:黃世傑黃世傑引用關係
指導教授(外文):Shyh-Jye Hwang
學位類別:碩士
校院名稱:國立清華大學
系所名稱:化學工程學系
學門:工程學門
學類:化學工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:中文
論文頁數:59
中文關鍵詞:內循環式流體化床環形區床-壁間熱傳係數納賽數
外文關鍵詞:internally circulating fluidizedannulusbed-to-wall heat transfer coefficientNusselt number
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內循環式流體化床是於傳統噴流床中加入一內管,使床質粒子在內管與環形區間流動,其粒子循環速率與氣體繞流的性質已有多位學者研究,但熱傳性質尚未有任何的探討。本實驗針對環形區床-壁間熱傳進行探討,使用的床體為內徑為9 cm,高2.5 m,內管直徑為4 cm,高35 cm的內循環式流體化床,以不同粒徑的矽砂及玻璃珠為床質、內管幾何結構、環形區氣速與靜床高為操作變數,探討各操作變數對環形區床-壁間熱傳係數的影響。
實驗結果發現,以254 mm與324 mm的矽砂作為床質,在相同的內管幾何結構、靜床高與環形區氣速時,床-壁間熱傳係數會隨著內管氣速的增加而增加,再達到一最大值,之後下降;以194 mm的矽砂與254 mm的玻璃珠粒子作為床質,床-壁間熱傳係數則隨著內管氣速的增加而增加。床-壁間熱傳係數隨粒子熱傳導係數與內管底部孔口直徑的增加而上升;隨著床質粒徑、內管底部孔口數、孔口與分散板間的距離與靜床高的減少而上升。當環形區操作氣體大於最小流體化速度時,多餘的氣體由於會造成上升氣泡使床-壁間熱傳係數變低。除此之外,由實驗結果提出一床-壁間無因次熱傳係數之關係式,且可準確預估床-壁間無因次熱傳係數。

An internally circulating fluidized bed (ICFB) reactor was used to study annulus bed-to-wall heat transfer. The inner diameter and height of the fluidized bed were 9 cm and 2.5 m, respectively. A concentric draft tube was located at the bottom of the bed. The heat transfer coefficient was measured by a heat transfer probe system similar to that of Basu et al. (1987). The effects of the physical properties of the bed materials, orifice diameter, orifice number at the same total orifice area, distance of the draft tube distributor to the orifice, static bed height, and superficial gas velocity at the annulus inlet on the annulus bed-to-wall heat transfer coefficient were investigated.
It was found that at a fixed gas velocity to the annulus, the annulus bed-to-wall heat transfer coefficient increased initially, reached a maximum value, and then decreased with increasing gas velocity in the draft tube. In addition, the heat transfer coefficient increased with decreasing distance of the draft tube distributor to the orifice, and particle diameter. A higher static bed height caused more solid backflowing to the draft tube, which decreased the solids circulation rate and the annulus bed-to-wall heat transfer coefficient. Besides, the annulus bed-to-wall heat transfer coefficient increased with increasing particle thermoconductivity coefficient and orifice number. A larger orifice diameter had a lower resistance for the solids circulation between the draft tube and the annulus, which resulted in a higher annulus bed-to-wall heat transfer coefficient. When the annulus inlet superficial gas velocity was greater than umf, excess gas might form bubbles, which reduced frequency of the solids contacting with the heat transfer surface. As a consequence, the heat transfer coefficient decreased. Furthermore, there was a maximum annulus bed-to-wall heat transfer coefficient at Red=14.75. An empirical correlation of the annulus bed-to-wall heat transfer in terms of Nusselt number was obtained as follows:
,

摘要
Abstract
謝誌
總目錄 I
圖目錄 III
表目錄 IV
一、 緒論 1
二、 文獻回顧 3
2-1 流體化床 3
2-1-1 粒子粒徑 3
2-1-2 最小流體化速度 4
2-1-3 終端速度 6
2-2 內循環式流體化床 7
2-2-1內循環式流體化床的構造 7
2-2-2內循環式流體化床的水力性質 9
2-2-3粒子循環速率量測方法 10
2-2-4氣體繞流率量測方法 11
2-3 流體化床床-壁間熱傳之研究 13
2-3-1 床-壁間熱傳係數的定義 13
2-3-2 影響床-壁間熱傳的參數 14
2-3-3 粒子物理性質對熱傳機制的影響 16
三、 實驗裝置與步驟 18
3-1 實驗裝置 18
3-1-1 流體化床反應器 18
3-1-2 熱傳探針系統 19
3-1-3 粒子循環速率的測量 20
3-1-4 氣體繞流率的測量 20
3-1-5 周邊設備及儀器 21
3-2 實驗步驟 22
3-2-1 實驗操作與溫度測量 22
3-2-2 操作變數 22
四、 結果與討論 26
4-1床-壁間熱傳係數與內管氣速(ud)之關係 26
4-2床-壁間熱傳係數與床質粒子物性之關係 29
4-3床-壁間無因次熱傳係數(Nu)與孔口直徑(dor)之關係 32
4-4床-壁間無因次熱傳係數(Nu)與孔口個數(N)之關係 35
4-5床-壁間無因次熱傳係數(Nu)與孔口開孔距分散板距離
(Hdo)之關係 39
4-6床-壁間無因次熱傳係數(Nu)與靜床高(Hs)之關係 42
4-7床-壁間無因次熱傳係數(Nu)與環形區氣速(ua)之關係 45
4-8床-壁間無因次熱傳係數(Nu)與各實驗參數間之關係式 50
五、 結論 52
符號說明 53
參考文獻 57

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