掃流微過濾之薄膜表面受力分析與阻力模擬

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Title:	掃流微過濾之薄膜表面受力分析與阻力模擬
Other Titles:	Simulation of force on membrane surface and resistance of membrane during cross-flow microfiltration
Authors:	李國禎;Li, Kuo-jen
Contributors:	淡江大學化學工程與材料工程學系碩士班吳容銘;Wu, Rome-ming
Keywords:	掃流微過濾;模擬;側流;結垢;平均孔隙度;cross-flow microfiltration;simulation;side-stream;fouling;average porosity
Date:	2007
Issue Date:	2010-01-11 05:37:38 (UTC+8)
Abstract:	已知在掃流微過濾中，施加在膜面上的流體力學之受力，為影響濾餅型態及整體過濾阻力的主要因素之一。在廣泛的操作條件下，過濾之濾速往往隨著掃流速度及過濾壓差的增加而增加。在此研究中，對於掃流微過濾的裝置建立出模擬的構造型態、模擬的空間網格，以及邊界條件之設定。在速度流場、整體的過濾阻力以及在膜面上的剪應力分佈均可藉由模擬計算出，並且與實驗結果相互對應。另外，在研究中乃利用側流(side-stream)的構思，希望改變濾室中的流力狀態，使膜面上的剪應力有所改變。針對實驗所得到之濾速値及配合使用計算流力(computational fluid dynamics, CFD)軟體加以模擬，探討是否會有改善薄膜結垢的情形、以及觀察膜面上之剪應力的變化情形，進而達到提升濾速的效果。針對膜面上作受力的分析，可助於延緩膜面上的阻塞速率和增進掃流微過濾效能之研究發展。在此使用計算流體力學之輔助軟體，可有效地助於如何設計過濾系統，進而增加濾速、減少膜面上的阻塞及延長過濾的水洗週期。最後，在濾餅的平均孔隙度變化上也加以分析探討。 It''s known that under cross-flow microfiltration, the major factors influencing cake formation as well as the overall filtration resistance were found to be the hydrodynamic forces exerted on the membrane. Therefore, the filtration rate increased with the increase of the cross-flow velocity and filtration pressure under a wide range of conditions. In this work the simulating geometry of the cross-flow microfiltration was established, the meshes were constructed, and the boundary conditions were set, then the velocity field, the total filtration resistance, and the shear force distribution on the membrane surface could be calculated directly. Then we compare these numbers obtained from simulations with experimental results. Also, we use the idea of the side-stream in this study with the hope of altering fluid dynamics inside the channel, which in turn causes changes in the shear force on the membrane. Combining the filtration rate obtained in experiments and the computational fluid dynamics (CFD) software, we attempt to improve fouling condition on the membrane and to observe alterations in the shear force on the membrane, all with the eventual goal of improving the filtration rate. The force analysis on the membrane surface is a tool for decaying fouling rate on the membrane and improving the efficiency of the cross-flow microfiltration. This CFD-aided design could help to effectively increase the permeate flux, reduce the fouling on the membrane and extend the washing cycle during filtration. Finally, we also discuss the varying average porosity of cake.
Appears in Collections:	[Graduate Institute & Department of Chemical and Materials Engineering] Thesis

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