迴路式熱管(LHP)為一種藉由相變化熱傳的兩相裝置，本研究的目標為藉由可視化的設計與穩態理論基礎，探討迴路式熱管在中溫範圍(200~500℃)的操作特性。實驗結果顯示一款新型可視化中溫迴路式熱管已成功被開發，藉由密封墊圈(Oring)與石英玻璃構成的可視化視窗，觀測毛細結構核心處(Wick core)延伸到補償室、蒸氣溝槽到蒸氣線入口(Vapor space)以及冷凝器內的兩相流流場變化，內部工作流體選用水，毛細結構使用自行燒結之玻璃毛細結構。在操作測試上此系統已成功啟動於40瓦，蒸發器表面溫度為82.7℃，最大操作瓦數為400瓦，其蒸發器表面溫度為506.7℃。此外本研究針對不同瓦數區間的觀察發現，熱洩漏佔比的大小會使得迴路產生不同的流場現象，如大量的蒸氣氣泡產生於毛細結構核心區或者冷凝器內液氣界面位置向後退縮的情形。而在不同傾角的熱傳表現上發現會受到毛細結構核心區的濕潤面積佔比與迴路的重力壓降影響而有所差異。

Loop heat pipe (LHP) is a two-phase device transfer heat by phase change. The goal of this thesis is to visualize experimentally the operation of LHP since the physical problems and the heat transfer behavior are complicated when the LHP operating in intermediate temperatures. The experimental design of visualization LHP consists of two parts. First, the optical transparent windows are installed on both sides of the evaporator and compensation chamber (CC), which are composed of quartz glass, O-ring, and flange. The volume of the liquid in the CC and liquid-vapor interface behaviors near the wick structure can be observed. Second, the transparent quartz tube is used to observe the two-phase flow in the condensation section. Water was selected as the working fluid. Glass powder was selected as the wick structure material. The experimental results show that the problem of intermediate temperature LHP was identified, it is found the heat leakage from the evaporator to the CC can lead to generate bubbles in the CC, therefore the back pressure inside CC is increased, the liquid-vapor interface moves backward in the condenser. Besides, the results from different tilt angles would be distinct due to the wetting area ratio of the wick core and the gravity pressure drop. In this study, the intermediate temperature is the evaporator maximum temperature can reach as high as 506.7°C if the input power of 400 watts is applied.

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