以溫度與速度同步量測技術探討突縮擴結構流場與熱傳增益

The development of simultaneous temperature and velocity measurements and applications on heat transfer analysis of in-lined/staggered cavities microchannel flow

陳裕婷(Chen, Yu Ting)

指導教授 ： 黃智永 ； 劉通敏

國立清華大學/工學院/動力機械工程學系/碩士(2015年)

摘要

本研究開發溫度與速度同步量測技術並應用改良後的技術於不同結構突縮擴微流道熱傳分析。同步量測技術是結合-PIV技術與life-time base TSP技術，選用相近散射波長的溫度螢光分子EuTTA與直徑3.2 m螢光追蹤粒子，再分別使用365 nm UV LED與532 nm雷射光源激發，利用兩種螢光分子的亮度差異分離同步量測影像中溫度與速度資訊後，再以後續影像處理分別分析轉換溫度與速度資料。實驗透過改變溶液濃度與螢光亮度分析方法，達到同步量測系統優化目的，並透過矩形微直管的驗證確認量測系統的準確性，並與前人的研究結果進行比較。本研究經改良後空間解析度與溫度靈敏度皆有所提升，空間解解析度可達2.69 m/pixel，溫度靈敏度於25~50℃區間可達4.32 s/℃。
本研究並將同步量測技術應用於對齊式與交錯式週期性突縮擴流道中，先以數值模擬探討雷諾數為25-200流場發展與熱傳增益，再以同步量測實驗結果比較討論。首先討論對齊式與交錯式突縮擴微流道的速度與溫度發展趨勢，由於本研究使用工作流體乙醇的Pr值為16，速度場的發展相當迅速，幾乎於第二周期及達到穩定發展。而根據液體溫度與紐索數的分析，溫度於第七、八週期接近穩定。在第八周期穩定發展區域內的流場中，成功以量測的速度資料觀察到重新接觸點位置隨著不同雷諾數與流道設計的變化。熱傳方面，對齊式流道於低雷諾數時熱傳增益成長較快速，但隨著雷諾數提高會逐漸受到結構中渦旋的限制，使得交錯式流道在高雷諾數時的熱傳增益成長幅度逐漸高於對齊式流道，當雷諾數為200時，交錯式突縮擴流道最高可達到2倍熱傳增益。

關鍵字

同步量測 ； 突縮擴流道 ； 熱傳增益 ； 溫度螢光感測 ； 微粒子影像測速

並列摘要

In this study, the simultaneous temperature and velocity measurements have been developed by integrating Micro Particle Image Velocimetry (μ-PIV) and Temperature-Sensitive Paint (TSP) system. The fluorescence molecule of EuTTA was chosen as temperature sensor and 3.2 m diameter fluorescence micro particles were used as tracers for velocity measurement, and they were excited by 365 nm UV LED and 532 nm laser respectively. The temperature and velocity information embedded in the luminescence images were separated by carefully distinguishing luminance difference during image processing. The molecular concentration and the acquired luminescent intensities have been adjusted to optimize the outcomes from simultaneous measurements. The modified experimental technique has been applied to a straight microchannel flow to examine and compare to the data from previous study.
The simultaneous velocity and temperature measurements were later applied to microchannel flow with in-lined/staggered cavities on the side walls and Reynolds numbers varying from 25 to 200. A commercial software ANSYS FLUENT was used to examine the flow fields with velocity and temperature development. Fast developing of velocity profile at microchannel entrance was observed in the flow field due to the high Pr number (16) of the working fluid (ethanol) selected in this study. The development of temperature in the in-lined/staggered microchannel flow has reached to fully developed region at the 7th to 8th structure. The re-attachment points have been calculated by the velocity profiles acquired by the experiments and they agree with simulation data. The heat transfer of microchannel flow with in-lined cavities is growing faster than staggered in low Re number regime. As the Re number increased, the heat transfer improvement of microchannel flow with staggered cavities becomes greater than the one with in-lined cavities, which is due to the change of vortex region behind cavity structures. The heat transfer improvement of microchannel flow with staggered cavities can be more than twice of straight microchannel flow while the Re number reaches 200.

並列關鍵字

simultaneous measurements ； cavities microchannel ； heat transfer ； TSP ； PIV

參考文獻

[1] R. J. Adrian, "Particle-Imaging Techniques for Experimental Fluid-Mechanics," Annual Review of Fluid Mechanics, vol. 23, pp. 261-304, 1991.

[2] C. D. Meinhart, A. K. Prasad, and R. J. Adrian, "A Parallel Digital Processor System for Particle Image Velocimetry," Measurement Science & Technology, vol. 4, pp. 619-626, May 1993.

[3] J. G. Santiago, S. T. Wereley, C. D. Meinhart, D. J. Beebe, and R. J. Adrian, "A particle image velocimetry system for microfluidics," Experiments in Fluids, vol. 25, pp. 316-319, Sep 1998.

[4] C. D. Meinhart, S. T. Wereley, and J. G. Santiago, "PIV measurements of a microchannel flow," Experiments in Fluids, vol. 27, pp. 414-419, Oct 1999.

[5] C. D. Meinhart, S. T. Wereley, and M. H. B. Gray, "Volume illumination for two-dimensional particle image velocimetry," Measurement Science & Technology, vol. 11, pp. 809-814, Jun 2000.