使用紅外線測溫儀量測系統研究矩形微流道內熱流發展區之對流熱傳

Using infrared thermography to study combined development in the entrance region of a rectangular microchannel

陳瑋瑄(Wei-Hsuan Chen)

指導教授 ： 潘欽

國立清華大學/原子科學院/工程與系統科學系/碩士(2013年)

摘要

摘要
本研究以紅外線測溫儀探討三氧化二鋁-水的奈米流體在矩形微流道內、熱流發展區內的強制對流熱傳遞效益與流量間及奈米顆粒濃度的關係。實驗採用鋁合金基材做為流道材質，而流道之長、寬、高分別為22mm、1.5mm及0.3mm，上方覆蓋一5mm厚的鍺玻璃做為紅外線測溫儀的可視化視窗。紅外線測溫儀可以提供高靈敏且非侵入式的空間溫度量測方法。本實驗建置一紅外線溫度量測系統，可直接觀測微流道內流體的溫度分佈，並且藉由T型熱電偶完成紅外線測溫儀量測目標物的溫度校正。另外，本研究以乙醇和純水的實驗分析結果與Lee與Garimella所發表的局部紐賽數預測式比較，其趨勢一致，可進一步說明此實驗量測系統之可信度與可行性與可信度。
本研究使用此紅外線溫度量測方法，探討奈米流體在層流下，微流道內熱發展區的對流熱傳情形。研究結果顯示，當奈米流體的濃度越高且流量越大時，其熱傳效果越好，熱傳增益值也較高。在奈米顆粒之質量分率為1wt%、質量流率為17g/min時，具有最大的熱傳增益值為1.64。

關鍵字

微流道 ； 紅外線測溫 ； 發展區 ； 對流熱傳

並列摘要

Microchannel heat sink with its high heat transfer area density and potentially high heat transfer coefficient has been proposed for applications with high heat fluxes. The objective of this study is to investigate single-phase convection in the combined developing region of a rectangular microchannel. An infrared thermography provides an effective approach for non-intrusive and spatio-temporal measurement of temperature. The entrance region, where the heat transfer coefficient is higher than that of the fully developed region, is of particular interest for microchannel cooling applications. The present study establishes an innovative benchmark experimental measurement uaing an infrared thermography. The experiments are conducted on a rectangular cross-section microchannel made of aluminum alloy 6061 with dimensions 22mm×1.5mm×0.3mm and covered on the top with a 5mm thick infrared transmitting germanium glass window. Consequently, the temperature distribution in the channel can be observed via the window directly. In order to measure the temperature correctly, all of the aluminum channel surface substrate was anodized such that emissivity can be increased to 0.95. The results show that the temperature distribution can be measured correctly using infrared thermography, and the local heat transfer coefficient can be acquired successfully. In order to validate the experimental system for measuring the local heat transfer coefficient, preliminary experiments with ethanol were performed. Finally, the results of the Lee & Garimella are compared with present experimental from the nusselt number with the axial positions.
　　Furthermore, this thesis reports an experimental method on the convective heat transfer of nanofluids. The nanofluid made of Al2O3 nanoparticles and de-ionized water, flowing through a aluminum rectangular microchannel in the laminar flow region. The results demonetrate considerable enhancement of convective heat transfer of the different concentrations of nanofluids.

參考文獻

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