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研究生:陳婕
研究生(外文):Chieh Chen
論文名稱:以計算流體力學套裝軟體FLUTNT數值模擬氣膠通過金屬編織網的貫穿率
論文名稱(外文):Numerical Simulation of Aerosol Penetration through Metal Woven Screens by the Computational Fluid Dynamics Package - FLUENT
指導教授:張幼珍
指導教授(外文):Yu-Chen Chang
學位類別:碩士
校院名稱:元智大學
系所名稱:化學工程與材料科學學系
學門:工程學門
學類:綜合工程學類
論文種類:學術論文
論文出版年:2007
畢業學年度:95
語文別:英文
論文頁數:81
中文關鍵詞:計算流體力學氣膠逃逸率金屬編織網
外文關鍵詞:computational fluid dynamics (CFD)aerosolpenetrationwoven metal screen.
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2005年鄭錦淑與張幼珍藉著分析金屬網獲得三維的斜紋織金屬網最小重複單元,並建立其三維模擬流體力學模型。本研究進一步發展其模型以獲得更完整的逃逸率曲線,結果顯示1.0 μm以下的粒子有別於陳春萬在2003年的實驗結果但仍符合預期,在流速為1 cm/sec時產生最大的差異,當流速為5及7 cm/sec,誤差值則在10%以內。接著尋求可能造成1 cm/sec誤差的原因:堆疊重複單元的研究證實可用單一重複單元作為整片金屬網作預期,粒子的初始速度對大於1.0 μm的粒子有極大的影響,但在本研究中沒有任何一個粒子初始速度的逃逸曲線可與實驗值完全重疊。另外,擴散及重力的影響也在本文中被討論。
本研究的最終目的是藉著模擬結果驗證勞工安全衛生研究所陳春萬的實驗。首先為節省計算記憶體,忽略邊界效應的影響,將金屬編織網簡化為單一重複單元。觀察實驗與模擬在不同流速下的逃逸率與Hinds (1999)的理論是否相符。之後再藉著排列重複單元來確定邊界效應對於逃逸率沒有太大的影響。最後,觀察不同流速、不同粒徑粒子的逃逸率並探討影響逃逸率的可能因素:擴散因子、重力、粒子速度可能造成的影響。
Previously, Cheng and Chang (2005) has developed a 3-dimensional model of the Twill weave metal screen by analyzing the woven screen to obtain the smallest repeating unit and then set up a 3-dimensional CFD model of the repeating unit. In this study, their model was further investigated to obtain complete penetration curves at three face velocities rather than penetrations at three particle diameters. It was shown that the predicted penetration agree with particles less than 1.0 ?慆 but deviates from those experimental data obtained by Chen (2003). The discrepancy was the largest when the face velocity was 1 cm/sec, while those of 5 and 7 cm/sec agree with experimental data rather consistently with an error within 10%. Further attempt was undertaken to investigate the possible causes for the discrepancy observed for the 1 cm/sec case. An investigation of deviation between predicted penetrations for single and multiple repeating units suggested a single repeating unit may be sufficient for the prediction of penetration. Also, the investigation of the effect of initial particle velocity on penetration for the 1 cm/sec case showed the initial particle velocity affects the predicted penetration of particles larger than 1.0 ?慆 in a significant way. For all initial particle velocities investigated herein, none of them overlaps with the experimental data completely. Lastly, the effect of diffusion and gravitational setting were also examined.
The final aim is proofing the results of Chen (2003) by simulating. For saving the memory neglects the effect of boundary layer and simplifies the metal woven screen to single repeating unit. Comparing the penetration of experiment and simulation fits the theory by Hinds (1999) or not. Then paralleling the repeating unit to makes sure there is no influence for boundary effect. Finally, observing the penetration of different face velocity and particle diameter and influences cause by particle diffusion coefficient, gravity, and particle velocity.
Abstract i
摘要 iii
致謝 iv
TABLE OF CONTECT v
TABLE OF FIGURES vii
TABLE OF TABLES xii
TABLE OF SYMBOLS xiii
Chapter 1 Introduction 1
1.1. Motivation of This Study 2
Chapter 2 Literature Review 3
2.1. Filtration Related CFD Study 5
2.2. Classical Theory of Aerosol Filtration 20
2.2.1. Penetration 20
2.2.2. Single Fiber Efficiency 22
2.2.3. Deposition Mechanisms 23
2.2.3.1 Interception 24
2.2.3.2 Internal impaction 25
2.2.3.3 Diffusion 26
2.2.3.4 Gravitational Settling 27
2.2.3.5 Electrostatic Attraction 28
2.2.4. Filter Efficiency 29
Chapter 3 Numerical Model 34
3.1. Description of Metal Woven Screens 35
3.2. Gambit Construction of 3-D Geometrical Shape of the Repeating Unit 37
3.3. Mesh Scheme of the Repeating Unit 43
3.4. Parameter Settings in FLUENT 45
Chapter 4 Results and Discussion 47
4.1. Penetration at Different Face Velocities 47
4.2. Comparison between Experiment and Simulation 51
4.3. Penetration of One and Two Joined Repeating Units 55
4.3.1. Repeating in z direction 55
4.3.2. Repeating in x and z directions 58
4.4. Deposition due to Diffusion and Gravitation Settling 61
4.4.1. Diffusional Deposition 61
4.4.2. Gravitation Settling 66
4.5. Particle Trajectories 69
4.6. Comparison of Particle Trajectories 72
Chapter 5 Conclusions 77
Chapter 6 Future Work 78
REFERENCE 79
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