目前用於改善薄膜蒸餾法極化現象造成之效率低下的方法，主要有紊流流道設計和施加超音波二種，但當前學術研究僅止於個別之物理機制和增益效果，故二種方法之結合是否有再增益的效果，實有研究之必要。
本研究使用直線流道與Z型流道，其進料端工作流體為純水，滲透端流速固定於0.06m/s，兩側溫差固定為15℃，以頻率為28kHz之法蘭式振盪板對流道施加超音波，調整超音波照射功率(0-108W)和進料端流雷諾數(Re=1110-5180) 進行測試，探討超音波結合非直線紊流流道設計對直接接觸薄膜蒸餾法之影響。結果顯示，未照射超音波時，二者之滲透通率皆隨雷諾數提高而增加，增幅於高雷諾數區趨緩，而Z型流道相對於直線流道可達7.6%之增益。施加超音波後，高雷諾數區對低功率超音波影響較不敏感，直線流道和Z型流道相對於其未施加超音波時之最大滲透增益分別為24.9% (Re=2035)及17.4% (Re=1110)。同時，推測低雷諾數之紊流內流場可能會抑制超音波部分效應；使用超音波增益薄膜蒸餾法時，其最大滲透通量有飽和值，此飽和值和流道種類無關而和雷諾數相依，並於接近臨界雷諾數時出現峰值。

There are two approaches frequently used to enhance the permeate mass flux in membrane distillation (MD). One is the special channel design to create turbulence earlier. The other is the irradiation of ultrasound. The focus of the recent study is about the physical mechanism and enhancement on MD for one of those, so it is necessary to explore what will be going on if we combine both of them in the system.
The effects of permeate flux enhancement for direct contact membrane distillation (DCMD) of pure water in the straight channel and zigzag channel with 28kHz ultrasound irradiation at a power in the range of 0-108W were tested. The Reynolds number of feed side varies in a range of 1110-5180, the velocity of permeate side and the temperature difference of both sides is fixed at 0.06m/s and 15℃ in the system. The results show that the permeation fluxes of both without ultrasound irradiation increase with increasing of Reynolds number but smaller rise under higher Reynolds number. The enhancement of zigzag channel in contrast to straight channel could reach 7.6%.
With ultrasound irradiation, the permeation fluxes of both are not sensitive to ultrasound under higher Reynolds number. The maximum enhancement in contrast to the flux without ultrasound is 24.9% for straight channel with Reynolds number of 2035 and 17.4% for zigzag channel with Reynolds number of 1110. The turbulent internal flows under lower Reynolds number may suppress the effects of ultrasound. Nevertheless, there is a maximum permeation flux for enhancing MD with ultrasound for any channel design which is only dependent on the Reynolds number. The peak of maximum flux appears if the Reynolds number is closed to the critical Reynolds number.

摘要 2
Abstract 3
致謝 5
符號說明 12
第一章 緒論 15
1-1 前言 15
1-2 薄膜蒸餾法之簡介 17
1-3 直接接觸薄膜蒸餾法之簡介 19
1-4 超音波簡介 21
1-5 文獻回顧 22
1-5-1 薄膜蒸餾法 22
1-5-2 超音波在水中的現象 22
1-5-3 超音波於薄膜蒸餾法中之應用 26
1-5-4 紊流流道設計 32
1-5-5 超音波對紊流邊界層之影響 40
第二章 理論分析 49
2-1 直接接觸薄膜蒸餾法(DCMD) 49
2-1-1 質量傳輸 49
2-1-2 熱量傳輸 50
2-1-3 溫度極化(Temperature Polarization) 52
2-2 超音波生成 54
2-2-1 超音波主機(Ultrasonic Generator) 54
2-2-2 壓電超音波換能器(Piezoelectric Transducers) 55
2-3 超音波在水中之現象 57
2-3-1 超聲空化現象(Ultrasonic Cavitation) 57
2-3-2 音波流動效應(Acoustic Streaming) 61
2-4 超音波對直接接觸薄膜蒸餾法之影響 63
第三章 研究方法 65
3-1 研究目標 65
3-2 實驗系統示意圖與設備 66
3-3 實驗變因 75
3-3-1 控制變因 75
3-3-2 操縱變因 75
3-3-3 應變變因 77
3-4 實驗步驟 78
第四章 結果與討論 81
4-1 直線流道 83
4-2 Z型流道 87
第五章 結論與未來展望 92
5-1 結論 92
5-2 未來展望 94
參考文獻 95
附錄 A 102
真空薄膜蒸餾法(Vacuum Membrane Distillation, VMD) 102
氣體掃掠薄膜蒸餾法(Sweeping Gap Membrane Distillation , SGMD)102
空氣間隙薄膜蒸餾法(Air Gap Membrane Distillation, AGMD) 103

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