懸浮微粒為一種主要的空氣汙染源，編織纖維濾網可以移除空氣中的微米和奈米顆粒。本研究使用二維結合晶格波茲曼與離散模式法預測編織纖維濾網的捕捉效率，並將模擬結果與已發表的參考文獻實驗結果比較。模擬模型使用了微米微粒和奈米微粒，懸浮微粒的尺寸介於0.3微米到100微米及3到20奈米。本論文結合了二個項目：第一個研究是微米粒子捕捉模型，氣體流速為每秒0.48公分，在此項目中使用了五種不同篩孔大小的濾網，篩孔大小從11微米到160微米；第二個研究則是奈米粒子經由篩孔大小126微米的不銹鋼編織濾網的捕捉模型，流體速度為每秒4.17、5.63和7.04公分，此外考慮了不同氣體溫度對捕捉效率的熱效應，溫度範圍介於296K至500K。本研究使用一圓形纖維濾網截面模型以模擬半無限排列纖維濾網，為簡化真實濾網的三維結構，分別使用了透過纖維編織濾網的物理特性所發展的五種二維模型：交錯編織篩孔尺寸模型、截面篩孔尺寸模型、開口面積模型、體積分率模型、修正方程式模型。與文獻實驗資料的比較結果顯示本模型可以準確預測濾網捕捉效率，另外透過粒子於纖維表面的分佈測試有助於了解在不同操作條件下的捕捉機理，本研究成果以期成為設計工具改善微粒過濾、空氣淨化等裝置。

The present study uses a 2D hybrid lattice Boltzmann-discrete phase model method to predict screen collection efficiency in woven wire screen. The computational results are used to compare with published experimental data that have not been computationally verified in the literature. The filtration processes are investigated for particles that are micron (0.3-100 μm) and nanometer (3-20 nm) in size. This thesis is composed of two subjects. The first study analyzes the filtration of microparticles at gas flow velocities of 0.48 cm/s via mesh screens with five different pore sizes in the range of 11-160 μm. The second study investigates the filtration of nanoparticles via stainless steel mesh screen with a pore size of 126 μm, where the filtration process is conducted with gas flow velocities of 4.17, 5.63 and 7.04 cm/s. Besides, the thermal effect on the filtration performance is revealed in the second study by varying the gas temperature (296K, 400K and 500K). For these two subjects, the computational domain contains a circular fiber that represents the cross-section of a semi-infinite fiber array. In order to simulate the 3-D woven screen structures, several 2-D models are proposed using different physical specifications of mesh screens including open area, pore size and packing density. The results show that the data predicted with a modified pore-size-based model are able to show excellent agreement with experiments. In addition, the particle distributions along the fiber surface are used to estimate the particle capture mechanisms together with the deposition patterns in the corresponding operational conditions.

論文審定書 i
致謝 ii
中文摘要 iii
Abstract iv
Table of Contents v
List of Figures vii
List of Tables xi
Nomenclature xii
1 Introduction 1
1.1 Background 1
1.2 Literature review 2
1.3 Objective 6
2 Computational details 7
2.1 Computational model 7
2.1.1 Model of microparticle filtration 7
2.1.2 Model of nanoparticle filtration model 10
2.1.3 Assumptions and structural mapping 11
2.2 Fluid phase equation 15
2.2.1 Lattice Boltzmann method 15
2.2.2 Boundary conditions 18
2.3 Particle phase equation 21
2.3.1 Transport equation 21
3 Results and discussion 27
3.1 Pressure drop 27
3.2 Screen collection efficiency 29
3.2.1 Screen collection efficiency for microparticles 29
3.2.2 Screen collection efficiency for nanoparticles 32
3.3 Particle distribution 34
3.3.1 Distribution of microparticles 34
3.3.2 Distribution of nanoparticles 39
3.4 Velocity contours and particle distribution 42
3.5 The force on the particle 44
4 Conclusions 46
5 References 47

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