摘要
由於高功率LED有著許多優點，因此近年來被廣泛的應用在各種照明之光源，特別是在汽車頭燈上的應用，更是許多廠商的重點科技。但由於LED本身的發光效率及壽命，將會隨著晶片溫度的升高而快速遞減，再加上LED汽車頭燈應用時需面對的引擎室高溫對於散熱設計的負面影響；所以如何在此惡劣的散熱環境中有效降低晶片溫度，以提升LED發光效率及壽命，將是高功率LED於頭燈上應用的重要關鍵。有鑑於此本文將針對一組LED汽車頭燈實體模型進行散熱設計，以數值模擬分析設計出有效之散熱模組，並藉CNC製造出散熱模組實體以配合實驗做模擬之驗證；經此數值模擬結合實驗驗證的研究方法，設計出能有效解決LED汽車頭燈散熱問題之方案，以提升高功率LED實際應用於汽車頭燈之可行性。
本研究利用計算流體力學分析軟體，針對高功率LED汽車頭燈的原始模型進行模擬分析與散熱設計，首先以單一投射模組進行較佳化之散熱設計，經過完整參數分析後設計出對於投射模組有較佳效能之散熱模組；再以此投射模組之較佳散熱設計為參考，套入整組LED汽車頭燈進行散熱設計，並整合實驗驗證與模擬分析之結果，確認出適用於此原型且具良好散熱效果之整體散熱模組設計。為滿足實際應用環境之需求，接著加入後方高溫影響來探討原始模型散熱設計之缺失，經由統整模擬分析結果之後；本研究提出新型具有與外界通風之散熱流道的燈殼設計，並將散熱模組設置於此流道內提升散熱效能，以此新型之散熱方案來解決LED汽車頭燈之散熱問題。最後之研究結果顯示此新型散熱設計具有相當良好之散熱效能，與原始設計相比可降低約20℃之效果，且能使LED晶片在90℃之安全溫度下運作，並且具有良好之均溫性。總結來說本研究所建立之結合數值模擬、CNC實體製作與實驗驗證的研發設計系統，將能幫助解決LED應用於汽車頭燈時之散熱問題，並可作為後續LED汽車頭燈散熱研究乃至一般LED燈具之參考與應用。

Abstract
Nowadays the application of high power LED as lightning source becomes popular because of several breakthroughs in recent years. Regarding its applications in vehicles, LED offers many advantages over traditional light sources. Other than its high lighting efficacy (lumens/Watt), low electricity consumption, quick response, and long lifetime, LED is generally small in size. This provides the design of vehicle headlamp greater flexibility and technology feel. However, the application of high brightness LED on vehicle headlamp faces some bottlenecks to breakthrough. Obviously, heat removal from LED chip to maintain low LED junction temperature is the most challenging task among them. Moreover, the high environment temperature, generated from the car engine, severely downgrades the heat-removing capability of the thermal module for LED headlamp. This will directly influence the radiation efficiency, emitted light quality, and lifetime of LED. Hence, this investigation focuses on the understanding and design of heat-rejecting mechanisms inside the LED headlamp for automobile through a combined effort of simulation, CNC mockup fabrication, and experimental verification.
In this study, ARTC LED headlamp mockup, which is developed by the Automobile Research and Testing Center (ARTC) in Taiwan, is chosen to perform this thermal task. At first, the thermal design and a comprehensive parametric study are imposed on a single LED project module to enhance its thermal performance, which is verified via CFD and experimental means. Then, this effective LED module and a new headlamp casing with a ventilation channel are proposed and applied on the thermal design of the LED headlamp to solve the heat-dissipation problem. Consequently, the results indicate that the numerical calculations agree well with the experimental outcomes. Also, the LED junction temperatures are located within the range of 84.2~85.7 °C, which are clearly well below the safety limit and yielding a small 1.5 °C temperature deviation among LEDs. In conclusion, this rigorous and systematic design scheme for LED headlamps has been successfully established and utilized to generate and fabricate an efficient thermal module to lower the LED junction temperatures by nearly 20 °C, compared to the corresponding temperatures of the original design.

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