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標題: | 高分子毛細結構參數對迴路式熱管性能之影響 Parametric Analysis of a Polymer Wick for Loop Heat Pipe |
作者: | Wei-Cheng Chou 周煒程 |
指導教授: | 陳瑤明 |
關鍵字: | 迴路式熱管,鹽溶濾法,高分子毛細結構, polystyrene,salt leaching,loop heat pipe, |
出版年 : | 2007 |
學位: | 碩士 |
摘要: | 本文旨在研究高分子毛細結構參數對迴路式熱管熱傳性能之影響。毛細結構為影響迴路式熱管性能的重要元件之一,目前毛細結構大多以金屬粉末燒結的方式來製作,其毛細結構參數(有效孔徑、滲透度、孔隙度)會受到金屬粉末粒徑、形狀、燒結溫度、燒結時間等因素所影響,因此不易控制其參數來進行探討。近年來,迴路式熱管逐漸朝向小型化發展,然而在朝小型化發展的同時,亦突顯了熱洩漏的問題,因此本文擬以生醫領域中的鹽溶濾法,搭配使用低熱導係數的高分子材料-聚苯乙烯來製作毛細結構,藉由改變氯化鈉粒徑大小及其在高分子材料中的比例來調控有效孔徑與孔隙度,進而探討孔隙度、有效孔徑與滲透度三者參數間之關係;經實際量測以鹽溶濾法所製作之高分子毛細結構,其有效孔徑量測值落於控制粒徑範圍內,孔隙度可精確控制於平均絕對誤差1.65%內,搭配不同的實驗參數,可找出滲透度與孔隙度之相關經驗公式 ,將有助於迴路式熱管之設計及熱傳性能上的預測。
實驗結果顯示,在製程條件允許下,當毛細結構厚度愈薄、有效孔徑愈小、孔隙度愈大時,其熱傳性能越好。故將毛細結構厚度1.75mm、孔隙度80%、有效孔徑 、滲透度 的高分子毛細結構置入迴路式熱管中進行熱傳性能測試,在蒸發器表面溫度85℃的限制條件下,熱傳量可達300W,熱阻為0.25 ℃/W,與相近參數之金屬毛細結構比較,其熱傳性能相接近。再者,高分子毛細結構相較於金屬毛細結構,在製作特性上具有製作成本低、參數易控制與加工性佳等優點,將有助於提昇迴路式熱管的應用潛力。 This research focuses on the parametric analysis of a polymer wick for the heat transfer performance of loop heat pipe. The parameters on the wick structure, including pore radius, porosity, and permeability. It is difficult to predict and control well in the manufacturing method of sintered metal powder. Then, small form factor LHP causes the problem of the heat transpiration easily. Therefore, polystyrene which is low thermal conductivity coefficient is chosen as the material and is fabricated by salt leaching. Adjusting the size of sodium chloride powder and its percentage in the polystyrene material, it could not only control the pore radius and porosity efficiently, but also be discussed the relationship of the parameters deeply among them. The results of the test show that the pore size parameter lies in the desired range, and the porosity is able to be controlled within 1.65% MAE. With repeatedly tests, a formula between permeability and porosity expresses as Kw=6.24×10-23ε6.87. Furthermore, this would promote both the LHP design and the prediction of heat transfer. What the results of the test reveal when the smaller the thinness and pore radius are, and the bigger the porosity is , the heat transfer would be much better. Hence, a wick structure with the thinness of 1.5mm, the pore radius of 0~20 micron, the porosity of 80%, and the permeability of 9.2×10-12m2 is installed into a LHP system to carry out the performance. The capacity of heat transfer in LHP with polymer wick structure approaches 300W, the thermal resistant is 0.25℃/W under the evaporator temperature of 85℃. The same result could be discovered within sintered metal powder method. In short, polymer wick structure, comparing with metal wick structure, has some advantages in the characteristics in its production, such as low cost, easily controllable, perfect processing, and so forth. Moreover, these merits would promote the potential of LHP as much as possible. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/28088 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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