Manufacturing and Investigation of the Effect of Sintered Nickel Wick Structures Produced by Debinding Process for Loop Heat Pipes

本文旨在研究小型化迴路式熱管之熱傳增強效應。首先進行毛細結構的乾涸限探討，其結果顯示：理想的熱傳能力存在於毛細壓力與滲透度間，受到有效毛細半徑與孔隙度的影響。唯有當有效毛細半徑小且滲透度高時，才能突顯其熱傳能力的增加。此外，孔隙度對有效毛細半徑與滲透度有相當大的影響。根據上述的結果，選定以增加開放性孔洞為主要探討的對象後，進行實驗研究。 在實驗過程中，利用脫脂加壓燒結法來控制有效毛細半徑，以獲得較高的毛細力，又因脫脂後所產生的開放性空孔數，使得滲透度增加，基於上述兩者優點來提升熱傳量。本實驗採用聚丙烯、石蠟、硬脂酸作為犧牲層，依據黏結劑的特性，將黏結劑加熱熔解並與鎳粉均勻混合，使黏結劑附著於鎳粉。藉由化學溶劑與加熱的方法能將黏結劑從毛細結構胚體中移除，進而形成較多的開放性孔洞 。 完成脫脂毛細結構後，將脫脂毛細結構應用於迴路式熱管，並測量其熱傳性能的表現。當有效孔徑約為4μm，孔隙度75%與滲透度為3×10^-12m^2的脫脂毛細結構置入迴路式熱管時，在容許溫度90℃與熱沉溫度40℃下，其最高熱傳量可達150W，熱阻為0.27℃/W。實驗結果顯示：脫脂毛細結構比起鬆粉毛細結構的熱傳性能約可增加40%。This study reports the investigation of the heat transport capacity enhancement in miniature loop heat pipe (mini-LHP).First, the theoretical analysis about dry-out limits of wick structures has been performed. According as the result of the theoretical analysis is to show that, optimum values of heat transport capability occur due to the influence of the effective capillary radius of curvature and porosity on both capillary pressure and permeability values. Besides, porosity is the most important function of the effective capillary radius of curvature and permeability values. According to the above-mentioned result, open pores have been chosen to discuss principally in the study. In the experiment, sintered nickel wick structures produced by debinding and pressuring process have been used in order to control the effective capillary radius of curvature and obtain higher capillary pressure. On the other hand, because of open pores produced by debinding process the permeability values can be increased. The maximum heat transport capability will improve on the basis of the foregoing two advantages. The binder system composed of polypropylene, paraffin wax, and stearic acid has been chosen to be the sacrificial layer in the study. Based on the properties of the binders, the binders are heated and uniformly mixed with nickel powders. The binders adhered to nickel powders. The binder system can be removed in order to form more open pores by chemical and heating ways. After debindering stages of the wick structure, the wick structures will be applied to LHP and measured the performances of heat transport capability. Wick structure produced by debinding process with the porosity about 75%, the mean pore size lies in 4μm and the permeability of 3×10^-12m^2is installed into a LHP system. The maximum heat transport capability of present LHP system approaches 150W, and the thermal resistance is 0.27℃/W when the performance test is conducted under the operating temperature of 90℃ and the heat sink temperature of 40℃. The testing results show that, debinding wick structures are better in heat transport capability than only loose powder sintering wick structures because this method can increase 40% in heat transport capability.中文摘要i 英文摘要 ii 目錄 iii 圖目錄 v 表目錄 vii 符號說明 viii 第一章 緒論 1 1.1前言 1 1.2文獻回顧 5 1.3研究目的 7 第二章 實驗原理及理論分析 8 2.1迴路式熱管操作原理 8 2.1.1毛細限制 10 2.1.2啟動限制 10 2.1.3液體過冷度限制 11 2.2壓降理論分析 12 2.2.1液－汽介面之毛細壓差 12 2.2.2蒸發器溝槽內蒸汽流動壓降 13 2.2.3汽體段流動壓降 13 2.2.4流經毛細結構之壓降 14 2.2.5液體段及冷凝段流動壓降 16 2.2.6重力壓降 16 2.3補償室體積與工質注入量 18 2.3.1補償室體積 18 2.3.2注入量 19 2.4毛細結構的乾涸限 20 第三章 實驗設備與方法 23 3.1實驗設備 23 3.1.1實驗材料 23 3.1.2製造設備 25 3.1.3測試設備 26 3.2實驗步驟 28 3.2.1脫脂毛細結構製作步驟 28 3.2.2迴路式熱管之安裝步驟 30 3.2.2性能測試步驟 31 3.3誤差分析 32 3.4實驗參數 36 第四章 結果與討論 37 4.1毛細結構的功能 37 4.2毛細結構的主要參數 37 4.2.1有效毛細半徑 37 4.2.2孔隙度 41 4.2.3滲透度 41 4.3毛細結構的理論分析 42 4.4脫脂毛細結構 45 4.4.1原料 47 4.4.1.1鎳粉 47 4.4.1.2黏結劑的選擇 47 4.4.2混合 48 4.4.2.1混合的模式 48 4.4.2.2混合種類的選擇 50 4.4.3設計與成型 53 4.4.4脫脂 54 4.4.5燒結 55 4.5性能測試 58 4.5.1毛細結構的性能測試 58 4.5.2毛細結構參數間的影響 61 4.5.3毛細結構的SEM觀察 64 4.5.4熱傳性能量測結果 71 第五章結論 79 5.1結論 79 5.2建議 80 參考文獻 81 附錄 8