在燃燒後捕捉製程中，常使用二氧化碳吸收塔進行碳捕獲。因此，如何減少碳捕獲的成本為一重要課題。在傳統二氧化碳吸收技術上，捕獲設備體積龐大是造成碳捕獲成本高的主要原因之一，由於氣液體質傳效率低造成需使用龐大設備體積來彌補質傳效率的問題。近年來，許多的二氧化碳捕獲製程的研究，均朝向如何改善吸收塔質傳效率改善的議題。吸收塔中的氣液接觸面面積是最重要的質傳參數，也因此氣液接觸面面積最受關注。
本研究提出以數個非實質上隨意排列的不規則填料推疊模型，取代隨意堆疊不規則填料之流場，利用計算流體力學(computational fluid dynamics, CFD)模擬方法評估填充物結構，模擬氣液雙向流在填料間的三維數值模擬，使用流體體積方法(volume of fluid, VOF)探討氣液體接觸面積與持液率(liquid holdup)在流場內部的情形與變化。並以流體體積方法來捕捉氣液交界面之移動。模擬結果顯示氣液接觸面積和持液率皆會隨著液體進口速度增加而增加。為了驗證模擬結果的準確性，將模擬結果與文獻關係式比較，結果顯示兩者之結果相當相近，證實了本模型的可行性。因此，本研究提出了一個可行之研究方法能有效地用來模擬隨意堆疊不規則填料之流場。

Post-combustion capture processes by using CO2 absorber are considered one of the options for Carbon Capture. Consequently, how to reduce CO2 capture cost is an important issue. Huge volume of the absorption equipment is the main cause of high CO2 capture cost. Traditional CO2 absorption equipment has drawback of huge volume, mainly because of the low gas-liquid mass transfer efficiency. That led to use volume of equipment to make up the problem of mass transfer efficiency. In recent years, there has been many studies of CO2 capture process toward improvement of absorber mass transfer efficiency. It is shown that the most important mass-transfer parameter is the interfacial area, hence, it has been deeply concerned.
In the present study, we propose an approach by arranging several artificial models randomly to substitute the real random packing fields. To begin with, we use CFD simulation to evaluate packing structure, with a focus on parameters such as the interfacial areas and liquid holdups. Three dimensional numerical simulations of gas-liquid countercurrent flow in random packings are performed. Interfacial areas and liquid holdups are investigated using the volume of fluid method. Moreover, the VOF method is used to capture the gas–liquid interface motion. Results show that interfacial areas and liquid holdups increase with increasing liquid flow rates. In order to validate the accuracy of our model, the simulations results are compared to several correlations from literatures, and find that our simulation result is analogous to the ones in the literature, which indicates our model is reliable. As a result, this work shows how our method can be used as an effective tool to simulate and provide related information on random packing fields.

摘要 i
Abstract ii
目錄 iii
圖目錄 vi
表目錄 viii
第一章 緒論 1
1.1研究背景 1
1.2文獻回顧 5
1.2.1填充物介紹 5
1.2.2不規則填料 5
1.2.3環型填料 6
1.2.4規則填料 7
1.2.5 CFD模擬軟體應用於填充物構型設計 8
1.3研究動機與目的 13
第二章 研究方法 14
2.1模擬簡介 14
2.2數值方法介紹 15
2.3統御方程式 18
2.3.1質量守恆方程式 18
2.3.2動量守恆方程式 18
2.3.3能量守恆方程式 19
2.3.4體積分率方程式 19
2.3.5紊流方程式 20
2.3.6狀態方程式 20
2.3.7表面張力 20
2.4流場幾何 21
2.4.1填充物堆疊方法 25
2.5邊界條件 26
2.6網格切割 26
第三章 模擬驗證分析 28
3.1模擬前處理建模 28
3.2流體物理性質設定 29
3.3邊界條件設定 29
3.4數值模擬設定流程 30
3.4.1前處理部分 30
3.4.2 FLUENT部分 31
3.4.3後處理部分 31
3.5實驗結果 31
3.6實驗驗證 33
第四章 模擬結果 36
4.1氣相體積百分率結果 36
4.2液體進口流速對氣液接觸面積之影響 37
4.3氣液接觸面積與文獻驗證比較結果 39
4.4液體進口流速對持液率之影響 42
4.5持液率與文獻驗證比較結果 43
第五章 結論 46
參考文獻 47

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