有鑑於科技隨時代之演進，電子元件之性能要求大幅提升，導致廢熱之生成功率升高，而尺寸又受制於電子產品的內部空間有限必須縮小，使得廢熱之熱通量高於 1 MW/m2。故本文透過數值模擬的方式對多孔散熱器於高功率電子元件之應用進行熱分析，期望透過多孔媒介植入流道中強化散熱器之散熱能力，將電子元件之溫度維持於操作溫度的範圍內，另一方面，比較不同微結構設計之多孔模型，期望進一步強化散熱能力，同時減低流體阻力，以達成較佳之散熱效益。
本文所分析之物理模型分為入口管路、多孔媒介、以及出口管路，其中流道長度分別為18.7 mm、8.5 mm、以及10.2 mm，截面為寬3.4 mm 高8.5 mm，以入口流速為0.05-0.5 m/s之工作流體水，對高達1 MW/m2之邊界熱通量進行散熱，以控制最大之壁面溫度於 以內為目標。
在流場的分析中可發現，多孔媒介的使用將造成壓降明顯的提升，使其在實際流道應用上有一定的流量限制；溫度場分析中則發現其顯著地提升系統之散熱能力，有效降低壁面溫度並減低壁面溫度之溫度梯度，而在不同的多孔模型比較中發現，多孔模型A與多孔模型B皆足以有效的達成溫度控制的目標，且整體而言雷諾數的提升對溫度控制與散熱能力的提升都有正向的影響，但由於熱傳增益的極限，應避開雷諾數高於1173.3以上之應用，另一方面，多孔模型A在流阻方面有較佳的表現，反觀多孔模型B則於散熱能力方面較為優異。最後在綜合比較流阻與熱傳增益之效益分析中，多孔模型A與多孔模型B則各擅勝場。整體來說，多孔模型A於較高流量下(Q > 200 cm3/min)的表現更佳，多孔模型B則於較低流量下的表現更為突出。而在不同工作流體的比較中發現，當流體之黏滯性降低時，多孔模型B之流體阻力降幅較多孔模型A顯著，而當熱擴散性上升時，多孔模型A與B之散熱能力無明顯差距。
由本研究之結果發現，多孔散熱器於高功率電子元件之應用深具潛力，搭配良好的管路設計，可以完美的達成散熱之目標，且隨著製程技術的演進，使微結構設計成為改良多孔散熱器新的突破點，能提供更好的散熱效益以達到降低成本之需求。

關鍵字: 多孔散熱器、高功率電子元件、微結構設計、效能指標
Key words: porous heat sink, high power electronic components, micro-structure design, figures of merit

In this research, two micro-structure models are developed to numerically investigate the fluid flow and heat transfer in a porous heat sink applied on high power electronic components. The micro-structure in the models are different, in order to achieve the goals of operating temperature control as well as effectiveness enhancement. A series of analysis is established to examine the model, including pressure drop, friction factor, wall temperature distribution, temperature control effectiveness, average heat transfer coefficient ratio, and figures of merit. According to the results, the pressure drop rise caused by the insertion of porous media exceeds the range of practical pump applications in the case of the highest inlet velocity, while the heat transfer enhancement of both models increases with increasing Reynolds number obviously as a whole. On the other hand, Model A has better performance on flow resistance, while Model B is better on heat transfer enhancement. Thus, when it comes to figures of merit, Model B performs well in lower Reynolds number, but Model A catches up and surpass its counterpart as Reynolds number increases. On the other hand, it is shown that the properties of working fluid play an important role on flow resistance performance and heat transfer enhancement. In conclusion, this research points out the potential of porous heat sink under high heat flux and produces a procedure to examine the design. In addition, a new perspective of improvement, micro-structure design on porous heat sink is proposed and needs further research.

Key words: porous heat sink, high power electronic component, micro-structure design, figures of merit

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