高效能LED燈之散熱研究

A Study on the Heat Dissipation of the High Efficiency LED Lamps

賴涵煙(Han-Yen Lai)

指導教授 ： 鄧治東

中原大學/工學院/機械工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200067

摘要

本文係以數值及實驗方法探討高功率發光二極體(Light Emitting Diode，簡稱LED)，以不同形式的散熱鰭片所能達到的散熱效能。而LED又可分為可見光及不可見光，可見光波長為介於450~780 nm，不可見光則介於850~1550 nm，高功率LED燈在瓦數大小的選擇也會對散熱造造成影響，而此研究是以9W及18W LED燈作實驗測試材。
影響散熱因素的鰭片需要考慮其材質、高度、形狀、鰭片間距數等變因，利用ANSYS Icepak12.1進行模擬計算出在不同鰭片幾何及不同LED燈具功率情況下，LED燈具系統溫度的變化量，經由模擬可預先得知散熱鰭片在設計之後散熱效能的差異性，進而選擇其較佳燈具系統為實作試片測試，可以避免設計錯誤或需求不符的情況發生，本文所選擇長寬尺寸為60×60 mm及80×60 mm作為模擬設計樣本，再加上以上所述變因參數進行探討，隨後，對實驗設計的規畫係利用密閉壓克力箱作為實驗環境，以木板做為LED燈架平台，將熱電耦貼合在LED裝置上之6處溫度設計量測位置，並在散熱鰭片上均勻塗佈Arctic Silver 5散熱膏，緊密的將LED燈及散熱鰭片貼合鎖緊，且利用溫度量測計記錄於不同時間點，量測LED燈具系統溫度上升變化情形，經由實驗數據再與數值模擬分析對照比較其差異性。
隨後，對實驗設計的規畫係利用密閉壓克力箱作為實驗環境，以木板做為LED燈架平台，將熱電耦貼合在LED裝置上之6處溫度設計量測位置，並在散熱鰭片上均勻塗佈Arctic Silver 5散熱膏，緊密的將LED燈及散熱鰭片貼合鎖緊，且利用溫度量測計記錄於不同時間點，量測LED燈具系統溫度上升變化情形，經由實驗數據再與數值模擬分析對照比較其差異性。
本文藉實驗量測與數值模擬所得結果並兩者間之比較及差異分析獲致以下結論：
（1） 以9-W LED燈組為例，實驗數值最大與最小值相差1.9℃，百分誤差為3.63％，而實驗值顯示陣列圓柱形鰭片在9-W LED燈其降溫效能最好(50.4℃)，與擠壓成形鰭片相差1.2℃，模擬值則在這兩類鰭片相差3.9℃。
（2） 以18-W LED燈組為例，擠壓成形鰭片在模擬與實驗都為表現較佳的散熱效果，在未加鰭片時，LED燈之溫度為92.49℃，加上擠壓成形鰭片則溫度平均降為76℃左右，相差值為16.49℃，若以未加鰭片LED燈組溫度為準，百分溫降效果為17.82％。
關鍵字：發光二極體，散熱鰭片

關鍵字

散熱鰭片 ； 發光二極體

並列摘要

The purpose of this study was to determine numerically and experimentally the effectiveness of heat dissipation associated with the light-emitting diodes (LEDs) with two power levels (9-W and 18-W) and a number of geometrical configurations for the heat-dissipation fins made by aluminum. It is known that the lights emitted by LED lamps can be divided into the visible and invisible ranges, with wavelength of 450~780 nm for the former and 850~1550 nm for the latter.
Many factors affect the effectiveness of heat dissipation for the fins – materials, heights, shapes, and spacing between adjacent fins. ANSYS Icepak12.1 was used to numerically simulate the profiles of temperature for the various LED lamp systems with a variety of geometrical configurations for the fins and two levels of power consumptions for the lamp systems. Resulting from the simulations, predictions of the differences of effectiveness for the design of heat-dissipation fins can be evaluated. Subsequently, a better LED lamp system resulting from the numerical study will be used for the experimental study. By doing so, errors in design and discrepancies in real-world need could be avoided. In this study, the dimensions of the bases used for attaching the fins by either machining or extruding were 60×60 mm and 80×60 mm. In addition, the various parameters affecting heat dissipation of the LED lamp systems mentioned above were included in the study.
For the experimental design, the test module was enclosed in a Pyrex box with the size of 40×40×40 cm, using plywood planks to fix and support the test module. In addition, thermocouples were attached to the LED lamp system to obtain temperature readings at six locations of the system. Furthermore, the heat-dissipating fins were firmly attached to the LED lamp with thermal paste Arctic Silver 5 spread in between. The experimentally obtained temperature readings were then compared with those obtained from the numerical simulations, followed by evaluation of the differences among those two sets of results.
The results obtained from this study were summarized as follows:
（1）For the 9-W LED lamp system, difference between the maximum experimental temperature reading and that of the minimum reading was 1.9 oC, with a percentage difference of 3.63%. The highest effectiveness for heat dissipation of the system was found to be the lamp system with arrayed circular columns (50.4℃), while that for the system with extruded fins was found to be 1.2℃ higher than the one with arrayed circular columns.
（2）For the 18-W LED lamp system, better heat dissipating effectiveness was achieved for the LED lamp system with extruded fins, both numerically and experimentally. For the system with no heat-dissipating fins attached, the temperature obtained for the lamp was 92.49℃; it was reduced to 76℃ for the lamp system with extruded fins. The temperature difference between the two readings was 16.49℃, resulting in a percentage temperature lowering effectiveness of 17.82% based on the lamp temperature reading with no fins attached.

Keywords：LED, Heatsink

並列關鍵字

LED ； Heatsink

參考文獻

[20] 楊國泰，「高功率發光二極體應用於側光式天花板燈具之熱管理研究」，碩士論文，中原大學機械工程研究所，2011年。

[1] 熊世康，「Part II LED散熱分析」，碩士論文，國立成功大學航空太空工程研究所，2008年。

[3] 呂宗蔚，「高亮度LED散熱系統之熱傳及效益研究」，碩士論文，國立成功大學工程科學研究所，2007年。

[4] J. P. Holman, Heat Transfer, 8th ed., 2004.

[5] T. Cheng, X. Luo, S. Huangl, Z. Gan, and S. Liu, “Simulation on thermal characteristics of LED chips for design optimization,” International Conference on Electronic Packaging Technology & High Density Packaging, 2008.