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.

M. Khayet and T. Matsuura, “Membrane Distillation Principles and Applications,” 2011.
【2】 M.S. El-Bourawi, Z. Ding and R. Maa,, M. Khayet, “A Framework for Better Understanding Membrane Distillation Separation Process,” J. Membr. Sci. 285, pp. 4–29, 2006.
【3】 M. Khayet, T. Matsuura, J. I. Mengual, “Porous Hydrophobic/Hydrophilic Composite Membranes: Estimation of Hydrophobic-layer Thickness,” J. Membr. Sci. 266, pp. 68–79, 2005.
【4】 P. Cattin, “Basics of Ultrasound Principles of Medical Imaging,” MIAC, University of Basel, 2013.
【5】 M. Legay, N. Gondrexon, S. L. Person, P. Boldo and A. Bontemps, “Enhancement of Heat Transfer by Ultrasound: Review and Recent Advances,” Int. J. Chem. Eng. 2011, pp. 1–17, 2011.
【6】 S. J. Lighthill, “Acoustic Streaming,” J. Sound Vib. 61 pp. 391–418, 1978.
【7】 J. R. Blake and D. C. Gibson, “Growth and Collapse of a Vapour Cavity Near a Free Surface,” J. Fluid Mech. 111, pp. 123–140, 1981.
【8】 J. R. Blake, B. B. Taib and G. Doherty, “Transient Cavities Near Boundaries. Part 1. Rigid Boundary,” J. Fluid Mech. 170, pp. 479–497, 1986.
【9】 J. R. Blake, B. B. Taib and G. Doherty, “Transient Cavities Near Boundaries. Part 2. Free Surface,” J. Fluid Mech. 181, pp. 197–212, 1987.
【10】K. S. Suslick, “The Chemical Effects of Ultrasound,” Science 247, pp. 1439–1445, 1990.
【11】W. B. McNamara, Y. T. Didenko and K. S. Suslick, “Sonoluminescence Temperatures During Multi-bubble Cavitation,” Nature 401, pp. 772–775, 1999.
【12】T. Kodama and Y. Tomita, “Cavitation Bubble Behavior and Bubble–shock Wave Interaction Near a Gelatin Surface as a Study of in Vivo Bubble Dynamics,” Appl. Phys. B 70, pp. 139–149, 2000.
【13】K. Yasui, “Influence of Ultrasonic Frequency on Multibubble Sonoluminescence,” J. Acoust. Soc. Am. 112(4), pp. 1405–1413, 2002.
【14】S. Nomura, K. Murakami and M. Kawada, “Effects of Turbulence by Ultrasonic Vibration on Fluid Flow in a Rectangular Channel,” Jpn. J. Appl. Phys. Vol. 41 Part 1, No. 11A, pp. 6601–6605, 2002.
【15】P. Tho, R. Manasseh and A. Ooi, “Cavitation Microstreaming Patterns in Single and Multiple Bubble Systems,” J. Fluid Mech. 576, pp. 191–233, 2007.
【16】M.E. Findley, “Vaporization Through Porous Membranes,” Ind. Eng. Chem. Process Des. Dev., 6 (2), pp. 226–230, 1967.
【17】R.W. Schofield, A.G. Fane and C.J.D. Fell, “Heat and Mass Transfer in Membrane Distillation,” J. Membr. Sci. 33, pp. 299–313, 1987.
【18】H. Li, E. Ohdaira and M. Ide, “Effect of Ultrasonic Irradiation on Permeability of Dialysis Membrane,” Jpn. J. Appl. Phys. 35, pp. 32–55, 1996.
【19】T. Kobayashi, X. Chai and N. Fujii, “Ultrasound Enhanced Cross-Flow Membrane Filtration,” Sep. Purif. Technol. 17 (1), pp. 31–40, 1999.
【20】C. Zhu and G. Liu, “Modeling of Ultrasonic Enhancement on Membrane Distillation,” J. Membr. Sci. 176 (1), pp. 31–41, 2000.
【21】I. Masselin, X. Chasseray, L. Durand-Bourlier, J.-M. Lainé, P.-Y. Syzaret and D. Lemordant, “Effect of Sonication on Polymeric Membranes,” J. Membr. Sci. 181 (2), pp. 213–220, 2001.
【22】S. Muthukumaran, K. Yang, A. Seuren, S. Kentish, M. Ashokkumar, G.W. Stevens and F. Grieser, “The Use of Ultrasonic Cleaning for Ultrafiltration Membranes in the Dairy Industry,” Sep. Purif. Technol. 39, pp. 99–107, 2004.
【23】H.M. Kyllönen, P. Pirkonen and M. Nyström, “Membrane Filtration Enhanced by Ultrasound: a Review,” Desalination 181 (1–3), pp. 319–335, 2005.
【24】A. Boubakri, A. Hafiane, S. A. T. Bouguecha, “Direct Contact Membrane Distillation: Capability to Desalt Raw Water,” Arabian J. Chem. , 2014.
【25】D. Hou, G. Dai, H. Fan, H. Huang and J. Wang, “An Ultrasonic Assisted Direct Contact Membrane Distillation Hybrid Process for Desalination,” J. Membr. Sci. 476, pp. 59–67, 2014.
【26】M. Qtaishat , T. Matsuura , B. Kruczek and M. Khayet , “Heat and Mass Transfer Analysis in Direct Contact Membrane Distillation,” Desalination 219, pp. 272–292, 2008.
【27】林辰翰, “直接接觸薄膜蒸餾法之產出效率研究,” 碩士論文, 動力機械工程學系, 清華大學, 2010.
【28】L. Martinez, F. J. Florido-Diaz, A. Hernandez and P. Pradanos, “Estimation of Vapor Transfer Coefficient of Hydrophobic Porous Membrane for Applications in Membrane Distillation,” Sep. Purif. Technol. 33(1), pp. 45–55, 2003.
【29】劉菊蓮, “直接接觸薄膜蒸餾法之熱質傳研究,” 碩士論文, 動力機械工程學系, 清華大學, 2009.
【30】F. J. Fuchs, “Ultrasonic Cleaning: Fundamental Theory and Application,” 1995.
【31】J. T. Bushberg, J. A. Seibert, E. M. Leidholdt Jr, and J. M. Boone “The Essential Physics of Medical Imaging,” 2011.
【32】P. Fabijanski and R. Lagoda, “Modeling and Identification of Parameters the Piezoelectric Transducers in Ultrasonic Systems,” 2011.
【33】S. Gade, “Sound Intensity (Part I. Theory),” Brüel & Kjær Tech. Rev. 3, pp. 3-39, 1982.
【34】K. Yasui, T. Tuziuti, M. Sivakumar and Y. Iida, “Sonoluminiscence,” Appl. Spectrosc. Rev. 39(3), pp. 399–436, 2004.
【35】Y. Tomita and A. Shima, “High-Speed Photographic Observations of Laser-Induced Cavitation Bubbles in Water,” Acta Acust. united Ac. 71(3), pp. 161–171, 1990.
【36】H. Mitome, “The Mechanism of Generation of Acoustic Streaming,” Electron. Commun. Jpn. 3 Fundam. Electron. Sci. 81(10), pp. 1–8, 1998.
【37】R. G. Raluya, R. Schwantes, V. J. Subiela, B. Peñate, G. Melián and J. R. Betancort, “Operational Experience of a Solar Membrane Distillation Demonstration Plant in Pozo Izquierdo-Gran Canaria Island (Spain),” Desalination 290, pp. 1–13, 2012.
【38】A. A. Busnaina, G. W. Gale, I. I. Kashkoush, “Ultrasonic and Megasonic Theory and Experimentation,” The Magazine of Critical Cleaning Technology, pp. 13–19, April 1994.