微管道電滲流物理特性之數值模擬; Numerical Simulation for the Physical Characteristics of Electroosmotic Flow in Microchannel

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题名:	微管道電滲流物理特性之數值模擬;Numerical Simulation for the Physical Characteristics of Electroosmotic Flow in Microchannel
作者:	黃經孝;Ching-Hsiao Huang
贡献者:	機械工程研究所
关键词:	外加電場流;誘導電場流;電雙層;電滲流;Electroosmotic flow;Flow-induced electrokinetic field flow;Electric double layer;Applied external electric field flow
日期:	2004-06-15
上传时间:	2009-09-21 11:46:41 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本文針對平板與矩形管微流道中考慮電雙層效應熱流場進行數值模擬。模擬流場的參數與範圍：雷諾數26.6~422.2，平板流道高度5~190 m，矩形管水力直徑維持在24 m而高寬比分別為1/4、2/3與1，工作流體離子濃度10-7~10-4M， (zeta potential)為 25~200mV，施加壓力差-103~-105N/m2，外加電壓104~105V/m。本文除驗證與進一步分析Mala等人(1997)的平板熱流場外，另分析不同驅動型式（誘導電場流：壓力差；外加電場流：電壓差）的矩形截面電滲流場，探討正或負值對平板和矩形管中電雙層靜電位勢、速度、電動力與黏滯力的影響。再將速度剖面與實驗值作比較。結果發現平板流與誘導電場流均有因傳導電流造成流速降低的現象。正或負會影響電雙層靜電位勢與外加電場流，平板流與誘導電場流則不受影響。穩態時作用於流道截面的電動力與黏滯力變化取決於不同流場驅動型式。考慮電雙層效應的平板流場，摩擦係數略高於傳統理論值；紐索數略低於傳統理論值。於電滲流（外加電場流）模型中加入壓力項，可形成特定電滲流速度剖面，可用於微流體的混合及分離。 A numerical study is performed to analyze the effect of electric double layer (EDL) on the behavior of flow and heat transfer for microscale channel flows. Both the parallel flow and rectangular duct flow are simulated. The parallel channel height varied from 5 to 190 m and the aspect ratio of the rectangular duct, with a fixed hydraulic diameter (24 m), is between 1/4 and 1. The electroosmotic flow in the two parallel plates is analyzed first and compared with experiments. Next the electroosmotic flow in a rectangular duct is studied in detail, including the flow driven-mode either by the imposed pressure difference or by the applied voltage difference. In addition, effects of positive or negative zeta potential ( ) on the electrostatic potential distribution, velocity field, electrokinetic and viscous force variation are also investigated. Predicted velocity profile revealed that the conduction current will retard the flow velocity in the parallel plate flow and the flow-induced electrokinetic field flow. Either positive of negative do affect the electrostatic potential of EDL and applied external electric field flow, but it will not influence the parallel plate flow and the flow-induced electrokinetic field flow. In addition, variations of the electrokinetic force and the viscous force depend on different driven-mode of flowfield. The friction coefficient of the parallel plate flow is slightly higher than the classical theory, and Nusselt number is lower than the conventional value. With including the pressure term in the electroosmotic flow (the applied external electric flow), specific velocity profile of electroosmotic flow can be manipulated, which is helpful to the mixing and separation of the microfluidics.
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