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曾憲中13

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鄭澤明, 曾憲中, 徐睿, 黃彥慈

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具多個發泡鋁材塊之180度圓形轉彎通道之熱傳特性實驗研究

Experimental study of heat transfer characteristics in a 180-deg round turned channel with discrete aluminum-foam blocks

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中華民國第十八屆車輛工程學術研討會

ROC eighteenth Vehicle Engineering Symposium

Keywords：熱傳、180度轉彎通道、發泡鋁材塊

Heat transfer, 180-deg turned channel, aluminum-foam blocks.

Abstract：180度轉彎通道得熱傳增益研究多年來受到廣泛的關注，因為包刮燃氣渦輪葉片的內部冷卻，高數旋轉加工機德內部冷卻、及電子裝備冷卻系統等都會運用到此類的熱設計，本研究以實驗方法探討多個發泡鋁材塊之180度圓形轉彎通道之局部與平均熱傳特性，以空氣為冷流，在槽到截面寬高比為1之180度圓形轉彎通道內裝置多個發泡鋁材塊(空隙率為0.90、孔密度10 PPI)，共計有四種通構型被測試，桔果指出，裝置發泡鋁材塊的位置其局部紐塞數為區域峰值，在直通道中上必面與底壁之局部紐塞數較高，在轉彎區則以外側壁之局部紐塞數較高，而內側壁之局部紐塞數都較低；與空槽到之平均紐塞數相比較，本研究所提出的四種構型槽道之平均紐塞數增加了74~140%，顯示加入發泡鋁材塊對熱傳有可觀得助益，而且交錯排列發泡鋁材塊在職通道時對熱傳得幫助是略大於對稱排列構型，整體而言，Model 3與Model 4 測試段(通道中全區都具有發泡鋁材塊)之平均紐塞數比Model 1與Model 2測試段(僅直通到中具有發泡鋁材塊)的高出約20~30%。

The issue about the heat transfer enhancement in a 180-deg turned channel has attracted many attentions due to the widely industry applications, including the internal cooling of the blades of gas turbines, the internal cooling of the high-rottional-speed manufacturing machines and the cooling system of electric equipments. This work experimentally investigated the local and average heat transfer characteristics in a 180-deg round turned channel with discrete aluminum-foam blocks. The air was used as coolant. Sever aluminum-foam blocks (0.90 porosity and 10 PPI pore density) were installed discretely in the 180-deg round turned channel with the square cross section. Total four kinds of test section were measured. The results indicate that the local peak values of the Nusselt numbers would appear at the positions of the aluminum-foam blocks. The local Nusselt numbers of the upper and bottom walls were higher than those of the side walls in the straight ducts; while the local Nusselt numbers of the outer side wall were higher than those of others walls in the turn. The local Nusselt numbers of the inner side wall generally were the lowest values. Besides, the average Nusselt numbers of the present porous channels were 74~140% higher than that of the empty channel, suggesting the significant heat transfer enhancement of the aluminum-foam blocks could promote heat transfer more efficiently then the symmetric aluminum-foam blocks did. The average Nusselt numbers of Model 3 and Model 4 (the whole channel filled with aluminum-foam blocks) were 20~30% higher than those of Model 1 and Model 2 (only straight ducts filled with aluminum-foam blocks).

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