蜂巢式散熱鰭片應用於高功率LED之研究

節能的議題帶起了高功率LED熱潮，相較於過去傳統的燈具，LED具有許多優勢，但是LED本身最大的難題在於散熱，過高的溫度會降低LED的發光效率、壽命、甚至式顏色改變。然而不論是傳統的散熱技術，或是較新型的散熱技術，在設計LED燈具上，皆難以降低成本使其普及大眾，因此發展新的散熱技術一直是重要的議題。蜂巢式散熱鰭片為蜂巢式熱沉(honeycombs heat sink)與煙囪效應(chimney effect) 的結合，雖稱之為鰭片，但本身並無鰭片，取而代之的是蜂巢般的孔洞，因此擁有體積小，重量輕的優勢，並且完全採自然對流散熱，成本低，可靠度高。本文研究的方式主要利用CFD-RC套裝軟體進行模擬分析，並配合實驗做驗證，主要針對幾何外型、傾斜角度、材質以及輕量設計做探討。幾何上影響散熱能力的是肋徑比與高度，肋徑比在解熱上擁有最佳值，而高度越高能解的熱並不會增加越多，理想的高度選擇約在6mm~10mm，可以解13~14W的熱，且重量約只有75g~125g，如果設計得當，重量還可以再減輕1/3且幾乎不影響散熱效能。由於是自然對流且配上煙囪效應，所以角度影響是必然的，但是研究發現在30度以內影響程度不到5%。另外對於節省成本的方式，採用模組式的組裝，實驗發現如果不採用一體成型，而用多片疊加的方式的話，接觸熱阻也僅總熱阻的1%，從模擬也發現，鋁材是最佳節省成本的材料，如果將材料換成純銅，效能僅提升2%，因為傳導熱阻在蜂巢式散熱鰭片裡僅佔總熱阻的10%左右。

關鍵字

蜂巢熱沉；煙囪效應； LED ；散熱；自然對流

並列摘要

Previous studies show that the lighting quality of LED largely depends on operating temperature. LED without thermal management may fail early due to thermal runaway, epoxy degradation, and thermal stress under high-operating temperatures. In this study, the performance of a honeycomb heat sink was investigated by experimentation and three-dimensional numerical models. Two kinds of honeycomb models were proposed to demonstrate the performance of a heat sink with single and multiple heat sources for LED thermal management. The performances of innovative honeycomb heat sinks depend on the number of cells, aspect ratio, and the rib-space ratio. The simulated results indicated that the performance varies a little when the conductivity is over 50W/mK. Compared to the simulated heat flux ratio 0.95, the measured heat flux ratio 0.93 at θ=30° was slightly lower. The measured performance of the lump and stack (5 pieces) honeycomb heat sink can respectively keep 13.761W and 13.338W under the dummy heater at 67 ℃ and the ambient temperature at 27 ℃. The innovative design with nine pieces of layers that are drilled to reduce their weight can effectively dissipate the heat by natural convection in the application of a high-power LED street lamp.

並列關鍵字

Honeycomb heat sink ； Chimney effect ； LED ； Natural Convection

參考文獻

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蜂巢式散熱鰭片應用於高功率LED之研究

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