黏性熱逸散對微流道中電滲流熱傳特性之影響

目前研究微流道內流體之熱流特性相關文獻，絕大部分侷限於牛頓流體的流動行為分析，然而許多用於實驗室晶片的生醫流體並不適合視之為牛頓流體，所以非牛頓流體於微流道內的熱流傳輸現象值得更深入的研究。在微流道中以電滲驅動流體的情況下，因外加電場產生的焦耳熱效應，及因摩擦力產生的黏性熱逸散皆可能對熱傳特性造成影響，故本研究旨在分析微流道內以電滲流方式驅動微流道內流體之熱傳機制，並探討焦耳熱及黏性熱逸散效應對熱傳之重要性。本文旨在探討黏性熱逸散對微流道中電滲流熱傳特性之影響，藉由求解電位場、動量及能量方程式可得到電雙層中之電位分佈、流體速度與溫度分佈及紐賽爾數。本文探討三個重要參數，即布林克曼數(Br)、流動特性指數(n)、焦耳熱參數(G)的相互影響下，對溫度分佈及紐賽爾數(Nu)之影響。不同的流動特性指數情況下，焦耳熱為正或負時，布林克曼數增加則無因次化溫度減少。在分析紐賽爾數(Nu)的分佈中，分別探討流動指數(n)為0.5、0.8、1.0、1.2及1.5時在不同焦耳熱參數(G)的情況下之溫度分佈，布林克曼數增加則紐賽爾數明顯減少，焦耳熱G值為負時，紐賽爾數會產生一奇異點的現象，此現象由於極小的值而導致極大的紐賽爾數；不管流體指數為n < 1剪切變稀(Shear thinning)或n > 1剪切增稠(Shear thickening)，紐賽爾數(Nu)變化的趨勢皆相似。

關鍵字

微流道；非牛頓流體；電滲流；焦耳熱；黏性熱逸散

並列摘要

Because of the rapid developments in micro-electro-mechanical systems and microfluidics such as microchannel heat sinks for electronic cooling, micro fluid pumps, and microfluidic devices for chemical and biomedical analyses, etc., it is highly desirable to understand the essentials of various fluid flows in microchannel. Electroosmosis has been used extensively to move packets of fluid through lab-on-a-chip based microsystems. Most of the previous studies pertinent to microchannel flows were concerned with Newtonian fluids. However, microfluidic devices are usually used to analyze biofluids which may not be treated as Newtonian fluids. Keeping these in mind, the objective of this investigation is to study non-Newtonian fluid flow and heat transfer introduced by electroosmosis in microchannels. The governing system of equations includes the electrical potential field, flow field, and energy equations. Effects of Joule heating and viscous dissipation are taken into account in the energy equation. Analytical solutions are obtainable for Newtonian fluid flow and for electroosmotic flow with specific values of non-Newtonian behavior index, numerical solutions are generated by an accurate finite-difference method because of the highly non-linear nature of the governing differential equations. Representative results for the dimensionless temperature profiles and the Nusselt number are presented for different values of governing parameters. In this study the effects of Brinkman number(Br),flow behavior index(n),and the Joule heating parameter(G) on the temperature distribution and Nusselt number are examined. It was show that the dimensional temperature profile decrease with by increasing the value of Br. The Nusselt number can be reduced by increasing the Brinkman number for both shearing thing fluid(n<1) and shearing thickening fluid(n>1).

並列關鍵字

Microchannel ； Electroosmosis ； Joule Heating ； Non-Newtonian fluid ； Viscous Dissipation

參考文獻

1. S. J. Kim and D. Kim, ”Forced Convection in Microstructures for Electronic Equipment Cooling”, ASME J. Heat Transfer, 121,pp.639-645, (1999).

2. H. Y. Zhang, D. Pinjala , T. N. Wong , K. C. Toh , and Y. K Joshi, ”Single-Phase Liquid Cooled Microchannel Heat Sink for Electronic Packages”, Appl. Therm. Eng., 25, pp.1472-1487, (2005).

3. G. L. Morini and , M. Spiga , ”The Role of the Viscous Disspation in Heated Microchannel”, ASME J. Heat Transfer, 129, pp308-318, (2007).

4. C. H. Chen”Forced Convection Heat Transfer in Microchannel Heat Sinks”, Int. J. Heat Mass Transfer, 50, pp.2182-2189, (2007).

5. T. Bourouinay, A. Bosseboeuf, J.-P. Grandchamp, Design and simulation of an electrostatic micropump for drug-delivery applications, J. Micromech. Microeng 7, 186-188, (1997).

國際替代計量

黏性熱逸散對微流道中電滲流熱傳特性之影響

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