呂理平臺灣大學：化學工程學研究所陶政隆Tao, Cheng-LungCheng-LungTao2007-11-262018-06-282007-11-262018-06-282006http://ntur.lib.ntu.edu.tw//handle/246246/52170本實驗是在內徑0.108m、高5.76m、頂端接有1.5m高擴大管的流體化床中，以五種不同粒徑的砂為研究對象；在不同氣體表面速度下利用不同軸向位置的壓力探針及熱傳探針，同時量測相對或絕對壓力擾動及床-壁間熱傳。藉由各別壓力擾動平均振幅的統計分析來決定床中粒子的流態轉移速度，以作為確定由氣泡流體化床轉移至紊流流體化的判斷指標，並由此了解流態轉移對床-壁間熱傳係數的影響。 　　由壓力擾動之統計分析可知，當氣體表面速度逐漸增加時，床中流態先是小氣泡組成之氣泡流體化，然後隨著氣泡的加大與駐塞出現，壓力擾動就逐漸激烈。當氣體表面速度為到達Uc後，大型氣泡隨之破裂，使床內結構趨向均勻的流態，壓力擾動逐漸減小。目前多數學者大都認同Uc為紊流流體化床的開始。接著，床中不均勻的兩相，逐漸趨向均勻的流態，床內擾動達一齊平點時，就是Uk所在，也就是紊流床的結束。　　 　　在床-壁間熱傳現象方面，床-壁間熱傳係數會隨著氣體表面速度之變化，呈現M型曲線，其中出現的hmin和hmax2乃相對於移轉速度的Uc和Uk，顯示床-壁間熱傳機構會隨流態的轉變而改變。另外，在氣泡流體化及紊流流體化中，床-壁間熱傳係數hw受靜床高的影響將視熱傳探針的位置而有所差別，但床-壁間熱傳係數皆會隨粒子粒徑減小而增加。　Gas velocities at which transition occurred from bubbling to turbulent fluidization were determined by measurement of pressure fluctuations at various axial positions in a 0.108m i.d., 5.76m high expanded-top fluidized bed. By the method of statistical analysis, mean amplitude of pressure fluctuations were used to determine the transition velocity from bubbling to turbulent flow regimes. On the other hand, the effects of different flow regimes on bed-wall heat transfer coefficients were also determined. 　　The results show that pressure fluctuations become violent as the superficial increases and the activity of bubbles intensifies progressively owing to the bubbles by coalescence and greater formation frequency of bubbles. When superficial gas velocity increases to Uc, the pressure fluctuations peak gradually decay at the onset of the turbulent regime. 　　For the heat transfer, the results showed that when the superficial gas velocity increased beyond Uc, the bed-wall heat transfer coefficient would increase again. Besides, the influence of static height of bed on the bed-wall heat transfer coefficient depends on where the heater position is. As to the relationship between the bed-wall heat transfer coefficient and the particle diameter, the results show that the former decreases with the latter in the turbulent fluidized bed.中文摘要..………………………………………………………………...I 英文摘要..................................................................................................III 目錄..........................................................................................................IV 圖表索引.................................................................................................VII 第一章 緒論..............................................................................................1 第二章 文獻回顧..………………………………………………………6 2-1. 床-壁間熱傳現象................................................................................6 2-1-1 流體化床床-壁間熱傳的研究................................................6 2-1-2 床-壁間熱傳係數之定義......................................................10 2-1-3 流體化床床-壁間熱傳的論點..............................................11 2-2. 從氣泡床到紊流床的流態轉變.......................................................14 2-2-1 移轉區的探討.......................................................................14 2-2-2 影響移轉速度的變因...........................................................16 第三章 實驗裝置與步驟........................................................................17 3-1. 實驗裝置...........................................................................................17 3-1-1 裝置簡介..............................................................................17 3-1-2 細部說明..............................................................................17 3-1-3 固體粒子性質......................................................................24 3-2. 實驗步驟...........................................................................................24 3-3. 壓力擾動訊號與溫度分佈的量測與處理.......................................26 3-3-1 壓力擾動訊號的量測與處理..............................................26 3-3-2 熱傳探針溫度分佈的量測與處理......................................26 第四章 結果與討論................................................................................28 4-1. 由氣泡流體化至紊流流體化之流態轉變....................................28 4-1-1 相對壓力擾動的量測.......................................................28 4-1-2 絕對壓力擾動的量測.......................................................35 4-1-3 流態轉變對壓力擾動的影響...........................................42 4-2. 從氣泡床到紊流床的床-壁間熱傳現象.......................................44 4-2-1 床-壁間熱傳係數和氣體表面速度之關係.....................44 4-2-2 單位置或雙位置同時加熱對床-壁間熱傳係數的影響.50 4-2-3 床-壁間熱傳係數和靜床高之關係.................................55 4-2-4 床-壁間熱傳係數和熱傳探針位置之關係.....................67 4-2-5 床-壁間熱傳係數和粒徑之關係.....................................68 4-2-6 床-壁間熱傳係數與文獻的結果比較.............................74 第五章 結果與討論................................................................................77 第六章 符號說明....................................................................................80 第七章 參考文獻....................................................................................83 第八章 附錄............................................................................................92 Appendix 1. Labview 數據擷取程式………………………….92 Appendix 2. 床-壁間熱傳係數的計算方式……………...……93en-US流體化床床-壁間熱傳fluidizedthesis