本研究以實驗觀察迴路式熱虹吸熱管之垂直冷凝器的冷凝現象，主要的實驗參數為冷凝器的構造與表面親疏水性，包括：表面做親水處理之銅管、表面做疏水處理之銅管，以及表面做親水處理之溝槽管。三種冷凝管之冷凝效率依序為疏水銅管、溝槽銅管，與親水銅管，疏水銅管之冷凝熱阻可低於親水銅管達2-5倍之多；溝槽銅管之冷凝熱阻約為親水銅管的一半。疏水銅管之冷凝屬滴式凝結，凝結水以間歇方式流下，當增長最快的上段液滴達臨界尺寸後即迅速落下，路徑中掃清下方的液滴；親水溝槽管與平滑銅管皆為膜式凝結，其中親水銅管內冷凝液膜受水的表面張力影響，在流下的過程中會聚集於管圓周的某區域，使壁溫沿圓周呈現非均勻分佈。親水溝槽管中的溝槽提供毛細力，使液膜厚度沿圓周呈現均勻分佈，其上段中之冷凝水因可聚集於溝槽中，故溝槽管的上段熱阻為三者中的最小，但溝槽壁形成較大摩擦流阻而減緩冷凝水流下的速度，故溝槽管下段中的液膜增厚幅度為三者中最大。此外，親水銅管與親水溝槽銅管下方迴路中冷凝水位均有明顯震盪，平均冷凝水位主要受蒸汽摩擦壓降影響。

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