超音波對薄膜蒸餾法(MD)產出效率的提升是一種對此過濾方法有希望的增進方式，超音波的幫助主要是因為超音波空化現象、音波流動效應、薄膜上的震動以及超音波加熱現象…等等。本研究主要針對超音波對直接接觸薄膜蒸餾法(DCMD)的影響，探討超音波強度(0.14~0.42W/〖cm〗^2)、超音波頻率(28~120kHz)、進料端流速(0.1~0.4m/s)、進料端溫度(40~60℃)以及進料端氯化鈉濃度(0~3.5wt%)對產出效率的影響。實驗中超音波經由水間接傳遞進入實驗模組，薄膜使用孔徑為0.22μm、厚度為150μm之PTFE薄膜。滲透端控制在0.1m/s流速以及25℃溫度。實驗中超音波空化現象以及流動現象是主要影響產出效率的因素，兩者皆主要受超音波強度以及頻率的影響。超音波的照射可改善DCMD薄膜上的結垢現象，延長使用壽命。產出效率的增進與超音波功率成正比，與頻率成反比，在溫差較低、流速較小、氯化鈉濃度較低的時候效果較好，增進比例最高達10.63%。

The use of ultrasound has been considered a promising way to enhance the efficiency of permeation for membrane distillation (MD) due to effects such as ultrasonic cavitation, acoustic streaming, vibration and acoustic heating…etc. In this study, ultrasound with the irradiation power of 0.14~0.42 W/〖cm〗^2 and the frequency of 28~120kHz is applied in the system of direct contact membrane distillation (DCMD) for the feed velocity of 0.1~0.4m/s, the feed temperature of 40~60℃ and the feed salinity of 0~3.5wt%. The inlet conditions on the permeate side are fixed at 0.1 m/s and 25℃. The PTFE membrane used is of 150μm thickness and 0.22μm pore diameter. The results imply that ultrasonic cavitation and acoustic streaming are the two major enhancement mechanisms which are mainly influenced by the power and frequency of the ultrasound. The problem of membrane fouling is found to be improved by ultrasound irradiation. The enhancement of efficiency generally increases with ultrasound power and decreases with frequency and is more perceptible at relatively low flow speed, salinity and temperature on the feed side. The maximum enhancement of permeation flux with ultrasound irradiation is 10.63% for the problem of interest.

摘要 II
Abstract III
Acknowledgement IV
目錄 V
第一章 緒論 1
1-1 前言 1
1-2 薄膜蒸餾法簡介 2
1-3 直接接觸薄膜蒸餾法簡介 3
1-4 超音波簡介 4
1-5 文獻回顧 5
1-5-1 超音波 5
1-5-2 薄膜蒸餾 9
第二章 基礎理論 13
2-1 直接接觸薄膜蒸餾法(DCMD)理論分析 13
2-1-1 質量傳輸 13
2-1-2 熱量傳輸 15
2-1-3 溫度極化 17
2-2 超音波的生成 19
2-1-1 超音波主機(Ultrasonic generator) 19
2-1-2 壓電效應(Piezoelectric effect) 20
2-1-3 超音波換能器(Ultrasonic transducer) 21
2-3 超音波在水中的現象 23
2-1-1 超聲空化(Ultrasonic cavitation) 24
2-1-2 音波流動效應(Acoustic streaming) 28
2-4 超音波對直接接觸薄膜蒸餾法的影響 29
第三章 研究方法 32
3-1 研究目標 32
3-2 實驗操縱變因 32
3-3 實驗觀察目標 33
3-4 實驗系統 34
3-5 實驗設備簡介 35
3-6 實驗方法 44
3-1-1 實驗前準備 44
3-1-2 實驗步驟 46
第四章 結果與討論 49
4-1 進料端流速與溫度影響 50
4-2 進料端氯化鈉濃度影響 51
4-3 超音波強度的影響 54
3-1-1 流速變化下之影響 54
3-1-2 氯化鈉濃度變化下之影響 58
3-1-3 溫度差變化下之影響 60
3-1-4 超音波頻率變化下之影響 62
4-4 超音波對薄膜壽命影響 64
第五章 結論與未來展望 66
5-1 結論 66
5-2 未來展望 67
參考文獻 69
附錄 A 74

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