指導教授：陳瑤明臺灣大學：機械工程學研究所江長佑Jiang, Jhang-YouJhang-YouJiang2014-11-292018-06-282014-11-292018-06-282014http://ntur.lib.ntu.edu.tw//handle/246246/263159迴路式熱管為一種具相變化的被動熱傳裝置，相較於傳統熱管，其優點有： 遠距熱傳輸、低熱阻與高熱傳量等。一般圓管型迴路式熱管必須加裝鞍部(saddle) 才能應用於平面熱源，但加裝鞍部不僅增加系統總熱阻，還會使蒸發器表面溫度 分布不均，以致於影響其性能，因此直接研究與開發平板型迴路式熱管將可改善 加裝鞍部之缺點。 為了開發廣泛運用之電子熱傳，需要更輕薄之熱傳元件，一般迴路式熱管常 用金屬作為毛細結構材料，但常有燒結溫度高以及金屬氧化的問題，因此，本文 欲尋找製程較便宜以及可重複使用之材料，由文獻得知，有部分學者研究高分子 作為毛細結構材料，其中較被學者使用的則是鐵氟龍材料，又由文獻得知平板型 迴路式熱管與圓管迴路式熱管相較之下，有較嚴重的熱洩漏 (heat leak) 問題，這 也是造成平板型迴路式熱管系統總熱阻較高的主要原因，高分子材料之熱傳導係 數極低，亦可解決平板嚴重熱洩漏問題。因此本文欲採用鐵氟龍材料取代鎳毛細 結構材料並搭配自再潤濕流體(Self-rewetting fluid)使其延緩乾涸現象的發生，提升 臨界熱通量，且探討採用鐵氟龍材料取代鎳毛細結構之可能性以及自再潤濕流體對 於鎳以及鐵氟龍兩種截然不同之毛細結構熱傳性能之影響。 實驗證實，本文所建立之平板迴路式熱管熱測試系統比較各文獻後，在熱傳 方面是一個有相當水準的系統，在此平板系統上之實驗具有相當的準確性。在使 用自再潤濕流體方面，以鎳作為毛細結構材料，自再潤濕流體可有效降低整體操 作溫度，電子熱傳之溫度限制之下(85度C )，利用自再潤濕流體可有效將以水為工 質之散熱瓦數由50W 提升至100W，熱阻亦由1.56K/W 降低至1.07K/W，此外， 亦可延緩乾涸現象發生，使得最大熱負載由250W 提升至325W，熱阻由0.67K/W 降低至0.42K/W，另一方面，利用鐵氟龍取代金屬毛細結構材料，則無預期之結 果，最大熱負載由325W 降低至75W，但熱阻由0.42K/W 提升至1.41K/W，其運 iv 作時由於鐵氟龍本身的疏水性質，導致工質補充不易，但發現鐵氟龍毛細結構經 過一次燒結程序後，即擁有與雙孔毛細結構雷同的雙孔徑分布曲線，推測其工質 選定得當將會在進行熱傳測試時毛細結構可有效地大小孔分工，進而提升熱傳性 能。Loop heap pipe (LHP) is a type of passive two-phase heat transfer device;compared with a traditional heat pipe, LHP possesses the following advantages: long heat transfer distance, low thermal resistance, and high heat transfer capacity. For a heat source with a flat surface, a saddle must be added to a normal cylindrical LHP’s wick, but doing so not only increases the total thermal resistance of the system but also renders the evaporator’s surface temperature non-uniform, effecting the overall performance of the LHP. To eliminate such problems caused by the addition of a saddle, this study investigates the use of LHP with a flat-plate evaporator. In order to target cooling of electronic products that often require small and lightweight heat transfer devices, most LHPs use metal as the wick’s material; however, metal wicks oxidize easily and also require high sintering temperature in the manufacturing process. Thus, this study looks for a different wick material that can allow for more cost-effective and more easily manufactured wicks; from literatures,high polymer materials have been studied for this purpose,and among them polytetrafluoroethene (PTFE) have shown greater potential. Previous studies on flat-plate LHPs have also found that, compared to cylindrical LHPs, flat-plate LHPs encounter more serious heat leakage problems, causing the total thermal resistance values to be higher than those of cylindrical LHPs; PTFE, with a very low thermal conductivity value, is a great choice for wick material to solve this problem. Therefore,this study chooses PTFE as wick material to effectively, with the use of self-rewetting fluid as working fluid, delay the occurrence of drying-out and increasing the critical heat load. This study then investigates the feasibility of replacing the conventional nickel with PTFE as choice for wick material. In addition, the effect of self-rewetting fluid on the heat transfer performances of two LHPs—one with a nickel wick and one with a PTFE wick—are compared and studied.Experimental results show that,compared to those of previous studies mentioned in literatures, the heat transfer performance testing system established in this study is reliable. Concerning the effect of using self-rewetting fluid instead of water as working fluid, for flat-plate LHP with nickel wick, the use of self-rewetting fluid effectively decreases the overall operating temperature of the system. Under 85°C, which is the typical target temperature for electronic devices, using self-rewetting fluid instead of water can increase the LHP’s highest heat load from 50W to 100W and decrease the lowest thermal resistance from 1.56K/W to 1.07K/W; since the occurrence of dry-out is also delayed as a result, the critical heat load is increased from 250W to 325W.Concerning the effect of using PTFE instead of nickel as wick material, under the vii aforementioned conditions, the performance of LHP with PTFE wick is actually worse than LHP with nickel wick; the critical heat load decreases from 325W to 75W, while the thermal resistance has no significant improvement, increasing from 0.42K/W to 1.41K/W. Since PTFE is hydrophobic by nature, it is concluded that, with water as working fluid, it is difficult for the working fluid to travel through the wick; however,the pore size distributions of manufactured PTFE wicks are very similar to those of biporous nickel wicks. Thus it is highly probable that, with the proper choice of working fluid, the biporous nature of PTFE wick can come into effect, showing great potential for high and even enhanced heat transfer performance of flat-plate LHPs with PTFE wicks.摘要 ..... iii Abstract ..... v 目錄 ..... ix 圖目錄 ..... xiii 符號說明 .....xvi 第一章緒論 .....1 1.1 前言 ..... 1 1.2 文獻回顧.....10 1.2.1 迴路式熱管文獻回顧.....10 1.2.2 高分子文獻回顧.....11 1.2.3 自再潤濕流體之研究文獻回顧.....13 1.3 研究目的.....13 第二章實驗原理與理論分析.....15 2.1 迴路式熱管的基本原理.....15 2.2 迴路式熱管的操作限制.....17 2.2.1 毛細限制.....17 2.2.2 啟動限制.....18 2.2.3 液體過冷限制.....19 2.3 工質填充量與補償室尺寸.....20 2.3.1 工質填充量.....20 2.3.2 補償室尺寸.....20 2.4 迴路式熱管的熱阻分析.....21 2.4.1 蒸發器熱阻.....21 2.4.2 蒸氣段熱阻.....22 2.4.3 冷凝器熱阻.....23 第三章平板型迴路式熱管之設計.....25 3.1 工質的選擇.....25 3.2 系統材質的選擇 .....29 3.3 傳輸管路與冷凝器.....30 3.4 補償室之設計.....30 3.5 毛細結構之設計.....31 3.5.1 毛細結構材料選擇.....32 3.5.2 毛細結構溝槽設計.....33 3.5.3 針對經由毛細結構熱洩漏的解決方法.....34 3.6 蒸發器之設計.....35 3.6.1 加熱方向.....35 3.6.2 散熱作用面積.....36 3.6.3 平面板形狀 .....37 第四章實驗設備與方法.....39 4.1 實驗材料與製造設備.....39 4.1.1 實驗材料.....39 4.1.2 製造設備..... 40 4.2 製造方法.....42 4.2.1 毛細結構製作.....42 4.3 平板迴路式熱管實驗設備與測試步驟.....43 4.3.1 毛細結構的參數量測.....43 4.3.2 熱傳測試步驟及評估.....47 4.4 誤差分析 .....51 4.5 平板迴路式熱管系統參數.....51 第五章結果與討論.....53 5.1 平板迴路式熱管系統平台.....53 5.2 應用自再潤濕流體於鎳毛細結構之平板迴路式熱管.....56 5.3 應用自再潤濕流體於PTFE 毛細結構之平板迴路式熱管.....58 第六章結論.....63 6.1 結論.....63 6.2 建議.....64 參考文獻.....65 附錄.....67 附錄Ａ 量測不準度分析..... 67 附錄Ｂ 熱電偶校正曲線..... 72 附錄C 實驗測試數據.....7610450473 bytesapplication/pdf論文公開時間：2017/08/08論文使用權限：同意有償授權(權利金給回饋學校)迴路式熱管平板蒸發器鐵氟龍自再潤濕流體thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/263159/1/ntu-103-R01522402-1.pdf