奈米流體熱傳導係數之量測

The Measurement of Thermal Conductivity of Nanofluids

張顯修(Hsien-Hsiu CHANG)

指導教授 ： 郭鴻森 ； 李基禎

大同大學/工程學院/機械工程學系所/碩士(2007年)

摘要

在本研究中，吾人將針對奈米流體凝聚問題，探討幾種適用於奈米流體中的溶劑，以改善奈米流體中奈米粒子因凝聚而導致沉澱的問題，實驗結果發現甘油和聚丙二醇#1000兩種溶劑，其懸浮效果最好。同時再探討奈米流體在不同濃度下其對熱傳性能的影響，並改善測量儀器的誤差。
本研究過程採用：甘油和聚丙二醇#1000兩種400ml溶劑，再分別添加氧化銅體積比為0.04%、0.08%、0.12%、0.16%、0.2%，而這些奈米粒子皆於工作溫度為40°C時製作，其熱傳導係數均隨著添加氧化銅的濃度增加而增高。對甘油奈米流體而言，較原本熱傳導係數增加 2.6%、6.7%、9.8%、12.9%、15.3%；而聚丙二醇#1000製成之奈米流體，較原本熱傳導係數增加 6.3%、12.5%、20.9%、32.8%、48.2%。
另外在甘油與聚丙二醇#1000溶劑400ml，工作溫度為4°C時，分別添加氧化銅，氧化銅佔整體體積比為0.04%、0.08%，對甘油而言，其熱傳導係數較原先者增加7.1%、14.3%；對聚丙二醇#1000而言，其熱傳導係數較原先者增加17.8%、31%，都比工作溫度在40°C時，所製作出的奈米流體都來的高。
故可得知，在製作奈米流體時，較低的工作流體溫度，會得到更小體積的金屬奈米粒子，在不同溫度與相同濃度下，有較多的表面積，更有機會增加碰撞次數，所以會比高溫工作流體所製作出的奈米流體的熱傳導係數還來的高。工作溫度40°C下所做出的奈米流體粒子大小約20～80奈米，而4°C下所做出的奈米流體粒子大小約20～50奈米，所以熱傳效率會有提升的現象，未來可將奈米流體實際的應用在循環式冷卻系統。

關鍵字

奈米流體，奈米粒子，氧化銅，熱傳導係數

並列摘要

This research would be based on nanofluid coagulation issue, comparing several kinds of solvents which could fit in nanofluid and discussing the precipitation problem caused by the coagulation of nanoparticles. The experimental result finds that glycerol and polypropylene glycol#1000 solvents are suspended better than others. Furthermore, this study investigate the thermal conductivity of nanofluids at different concentration and improve the measuring equipment error.
Two kinds of 400ml solvents are adopted in the experiment: glycerin and polypropylene glycol#1000, and the proportions of copper oxide volume are 0.04%, 0.08%, 0.12%, 0.16%, 0.2%. At 40°C, the thermal conductivity is becoming higher when the concentration of copper oxide increases. The thermal conductivity of glycerol nanofluid increases 2.6%, 6.7%, 9.8%, 12.9%, 15.3% than pure fluid of glycerol. And the polypropylene glycol#1000 increases 6.3%, 12.5%, 20.9%, 32.8%, 48.2% than pure fluid of polypropylene glycol#1000.
At 4°C and the proportions of copper oxide volume are 0.04%, 0.08%, the thermal conductivity of glycerol nanofluid increases 7.1%, 14.3% and polypropylene glycol#1000 nanofluid increases 17.8%, 31%. This result shows that the thermal conductivity of nanofluid at 4°C is higher than that at 40°C.
According to the results, the lower working temperature of making nanofluid is, the smaller nanoparticles will be got. Under different temperature and the same concentration of cooper oxide, there would be more surface area so that it will increase numbers of collision and would make thermal conductivity of nanofluid higher than when making it at higher working temperature. At 40°C, the nanoparticle size is about 20- 80nm; at 4°C, the nanoparticle size is about 20- 50nm. The thermal conductivity efficiency is promoted. In the future, nanofluid could be put into practice in circulation cooling system.

並列關鍵字

thermal conductivity ； copper oxide ； nanoparticle ； nanofluid

參考文獻

【18】許健力，“奈米流體之熱傳效能分析”，中原大學碩士論文，2002。

【1】C Maxwell, “A Treatise on Electricity and Magnetism”, 2nd ed, pp435-441, 1904

【2】RL Hamilton and OK Crosser, “Thermal conductivity of Heterogeneous two-componentsystems”, Ind&EngrChemFundamental, pp 187-191, 1962

【3】AS Ahuja, “Augmentation of heat transfer in laminar flow of polystyrene suspensions”, JApplPhys46, 3408-3425, 1975

【4】KV Liu, SUS Choi and KE Kasza, “Measurement of pressure drop and heat transfer in turbulent pipe flows of particulate slurries”, Argonne National Laboratory Report, ANL-88-15, 1988