摘要
本文藉由實驗及數值模擬同時進行，分別以純水及機能性流體(正二十烷奈米乳液)進行增設同心圓管之等熱通量管內層流強制對流所帶來的傳熱效益。
實驗中，以銅做為圓管材料，外管尺寸為:長度1250mm，外徑10mm、內徑9.1mm。內管尺寸為:長度2060mm，外徑8mm、內徑7.4mm。內外管間隙為1.1mm。於銅管加熱段部分纏繞緊密的鎳鉻電阻線圈提供等熱通量加熱條件。
外部的操作條件包括奈米流體之質量分率 、入口溫度 、總體積流量 及加熱段所提供之熱通量 ，並調整內/外管流量比 同時進行數值模擬，配置出最佳的熱傳增益。
目前，進行內外管皆以基底流體之實驗模擬比較，為證明增設同心圓管後，內管在高流速下所帶來其流體載熱可大幅提升管層流內強制對流所帶來的熱傳增益，基底流體結束後即進行奈米相變化乳液。然而可以預期的是奈米乳液於相變化階段潛熱所帶來散熱增幅，並同時研究奈米乳液之密度、比熱、及熱傳導率，以及使用相變化材料因流體黏度增加所需而外付出的壓降。
於固定總流量及加熱功率之實驗條件，熱傳增益與流量比成正比關係，而若工作流體為奈米乳液，需在潛熱有發揮的情形下流量比越高熱傳效果才會高過於純水。在固定總流量於 中， = 2%、5%兩個濃度的奈米乳液分別在加熱功率110W流量比0.7及加熱功率110W流量比0.27，熱對流增益擁有1.32倍及1.88倍的最佳增益。
關鍵字：同心雙圓管、奈米乳液、相變化材料、層流強制對流

In present study demonstrates, via heat transfer experiments complementary with numerical simulations, the feasibility of achieving enhanced forced convection heat transfer of laminar water flow in an isoflux heated circular tube by inserting a concentric circular tube and controlling the concurrent flow distribution through the resulting concentric double-tube duct. In the experiment, copper was used as the material of the round tube, and the outer tube size was: length 1250 mm, outer diameter 10 mm, inner diameter 9.1 mm. The inner tube has a length of 2060 mm, an outer diameter of 8 mm, and an inner diameter of 7.4 mm. The inner and outer tube gap is 1.1mm. A tightly wound nickel-chromium resistance coil is provided in the heating section of the copper tube to provide iso-flux heating conditions. In the experimental conditions of fixed total flow and heating power, the heat transfer gain is proportional to the flow ratio. If the working fluid is a nanoemulsion, the higher the heat transfer effect will be higher than the pure water. . In the fixed total flow rate, the nanoemulsions with concentration of 2% and 5% are respectively in the heating power 110W flow ratio 0.7 and the heating power 110W flow ratio 0.27, and the convection has the best gain of 1.32 times and 1.88 times.

Key words: Concentric double tube, Nano-PCM emulsion, Phase change material, Laminar forced convection.

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