近年來由於LED的進步，低功率LED已廣泛地應用於車輛的指示燈與尾燈，唯獨車頭燈尚未被廣泛的運用，主要因其車頭燈必須使用高功率LED方能達成照明之應用，而高功率LED則受到輸入功率高，使得散熱問題非常受到關注，因此在高功率LED的應用若無有效的熱管理機制，將容易造成LED因為溫度過高而造成燒毀。有鑑於此本文透過專利檢索，其運用於LED車頭燈之相關散熱技術作一匯整，並將所檢索之專利加以探討與分析，且針對一款待開發LED車頭燈設計出符合量產化之散熱模組，配合商業套裝軟體FLUENT進行三維熱流場分析，以了解整體頭燈熱流場分佈趨勢而得到較佳化之設計，並將其較佳化之設計實際製造出原型LED車頭燈，並透過恆溫箱進行實際量測將其數據與模擬值作一比較，以探討本文所建構之模擬結果與實際量測間之誤差。實驗結果顯示六顆LED之晶片接合點溫度為104.7~110.3 °C皆在安全工作範圍之內，在考量熱阻值下所模擬之結果其誤差也在3％以內，在此足以證明本文所建構之數值模擬方法具有其相當之可信度，藉此本文進而以模擬的方式探討不同於量產型之自然對流散熱方案，其中在結合散熱模組之氣流道方案中晶片接合點之最高溫下降至103.3 °C，即為本研究於自然對流中所模擬出較佳之散熱效能；最後本文再以數值模擬探討量產型LED車頭燈行駛狀態下可能造成的溫度變化，以幫助後續相關研究與開發之人員評估LED機車頭燈於實際應用時的溫度狀態。

Recently, the technical advance of high-power LED has drawn a serious consideration to apply it on the headlamps by many automobile manufactures. Regarding its application on vehicles, LED offers many advantages, such as quick response, compact size, and high lighting efficacy, over the traditional light sources. However, the application of high-brightness LED on vehicle headlamp still faces some bottlenecks to breakthrough. Obviously, heat removal from LED chip to maintain low LED junction temperature is the most challenging task among them. Active cooling solutions are rarely considered as a practical solution due to cost and reliability concerns for vehicle applications. Therefore, under the natural convection constraint, this investigation intends to design the heat-rejecting mechanisms inside a motorcycle LED headlamp through a combined effort of numerical simulation, mockup fabrication, and experimental verification.
At first, a comprehensive CFD simulation is executed to check the thermal dissipation performances for several proposed thermal modules, which are featured with heat sink and connecting mechanism. Then, the best thermal module is fabricated via CNC and used to perform this thermal experiment in an isothermal chamber. It is shown that the numerical results agree well with the experimental outcomes for utilizing an appropriate contact thermal resistance. Also, the LED junction temperatures are located at the range of 104.7~110.3 °C, which are evidently well below the safety limit (125 °C). Moreover, ventilation channel with an extended cooling fin inside it is imposed on the thermal module to further enhance its dissipating capability. Numerical result indicates that the highest junction temperature can be reduced to 103.3 °C, which represents a significant 7 °C improvement. In conclusion, the accomplishment of this research offers a rigorous and systematic design scheme for the motorcycle LED headlamp. This design scheme has been successfully utilized to generate and fabricate an efficient thermal module to control the LED chip temperature below safety limit. In addition, the LED thermal modules for automobile can then be undertaken by following the similar procedure.

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