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Title: 氧化鋁奈米流體應用於熱管熱性能研究
Thermal Performance of Heat Pipes with Alumina Nanofluid
Authors: 徐昊杲
How-Gao Hsu
Tun-Ping Teng
Bo-Gu Lin
Keywords: 奈米流體
Heat pipe
Tilt angle
Issue Date: 2011
Abstract: 本研究使用二階合成法搭配水溶性幾丁聚醣分散劑製作出穩定懸浮的Al2O3/water奈米流體作為熱管的工作流體,並針對分散劑添加量對於Al2O3/water奈米流體的分散特性、熱傳導係數與流變等特性進行評估。最後再將最佳分散劑配製參數的Al2O3/water奈米流體實際應用於熱管之中,針對不同濃度、熱管長度、傾斜角、充填量與加熱功率的條件之下,探討各實驗參數對熱管熱性能的影響。研究結果顯示,在分散劑用量選擇方面,考慮分散特性與熱傳導係數兼顧之下,選擇添加0.2 wt.%的幾丁聚醣作為後續熱管性能實驗的分散劑濃度。在熱管性能實驗方面,當熱管傾斜角度為30°與充填量為20~40%時,會獲得較佳的熱傳性能,並且在加熱功率越高的狀況下更趨於明顯。在熱管長度對於熱性能影響方面,在相同的散熱能力之下,熱管長度越短,熱管內部工作流體輸送速率較快且管壁阻力相對較小,造成熱管無法在冷凝端進行良好的熱交換,故顯示出熱管長度越長時,其單位長度的熱阻越小。在整體效率提升方面,30cm熱管約可提升熱性能18.72%~43.78%,45cm熱管約可提升熱性能13.13%~50.72%,而60cm因本身熱阻較低,故熱性能提升約7.44%~17.67%。研究結果顯示,使用Al2O3/water奈米流體作為熱管的工作流體能比去離子水擁有較佳的熱輸送性能,對於高性能熱管的開發具有相當的潛力。
In this study, a two-step synthesis with a water-soluble dispersant of chitosan was used to produce stable suspensions of Al2O3/water nanofluid as the working fluid of the heat pipe. The thermal conductivity and rheological properties of the alumina/water nanofluids were evaluated. The optimal amount of added dispersant for the Al2O3/water nanofluid was determined. This study presents a discussion of the effects on the thermal performance of the heat pipe of the charged amount of working fluid, the tilt angle and length of the heat pipe, the heating power of the evaporator section, and the weight fraction of nanoparticles. The experimental results show that the optimal concentration of dispersant was 0.2wt.% to follow-up heat pipe thermal performance experiments under the dispersion properties and thermal conductivity simultaneously were considered. In thermal performance experiments, the optimal thermal performance of the heat pipe occurs when the tile angle of the heat pipe and the charged amount of working fluid are 30∘and 20 %~40 %, respectively. The shorter heat pipe is suitable for use in low heating power, and the longer heat pipe is suitable for use in high heating power applications under the same cooling condition. The 30 cm heat pipe can enhance the thermal performance efficiency by 18.72 %~43.78 %, the 45 cm heat pipe by 13.13 %~50.72 %, and the 60 cm heat pipe by 7.44 %~17.67 % when compared with deionized water as the working fluid of the heat pipe. This study confirmed that the Al2O3/water nanofluid has superior heat transport performance in the heat pipe compared with deionized water, and has considerable potential for use in the development of high performance heat pipes.
Other Identifiers: GN0698700406
Appears in Collections:學位論文

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