本研究利用表面改質方法定義不同濕潤表面圖形設計於銅管外壁，主要目的為增大銅管冷凝熱傳效率與冷凝水收集速率，以提升冷凝器內部銅管整體冷凝熱傳性能。由於冷凝器內部銅管外壁為一彎曲表面，為此本研究自製曲面網版印刷平台，並應用網版印刷技術設計及製作不同濕潤表面圖形於銅管彎曲表面，主要目的為提升製作便利性與降低製作成本。本研究製作之銅管表面包括超親水銅管、超疏水銅管及三種梯度銅管表面。三種梯度銅管表面設計分為單楔形θ=8°、14°與雙楔形θ= 8° 並進行不同濕潤定銅管表面冷凝熱傳實驗及冷凝水收集速率實驗，並與未改質純銅管表面進行比較，研究結果發現在固定實驗條件之下，雙楔形8°之梯度銅管表面冷凝熱傳效率與冷凝水收集速率最佳。單楔形8°及單楔形14°冷凝熱傳係數高於未改質純銅管表面，但略差於超疏水銅管，本實驗結果顯示在表面過冷溫度ΔT < 12 °C時，雙楔形8°之梯度銅管表面冷凝熱傳係數高於純銅管，冷凝熱傳效率最高可提升28%，主要原因為楔形與楔形陣列之間最大液滴D max =1.479mm時就能被驅動，相較於其他性質銅管表面，液滴在雙楔形θ=8°表面上有較快驅動速度，可加速液滴從表面上滑落。

Condensation is a phase change phenomenon often found in nature, as well as used in the applications including thermal management, desalination, and power generation. For the past decades, researchers are able to create surfaces that allow droplets to be easily condensed and removed for enhanced heat transfer performance. Recent achievements in micro/nano fabrication techniques have enabled control of surface wettability. Condensation surface with proper design of wettability patterns can have higher droplet mobility which can promote droplet coalescence. Here, we provide a new surface modification method based on screen printing techniques to define superhydrophobic and superhydrophilic areas on copper tube curve surfaces for enhanced condensation heat transfer. In this study, screen printing platform is utilized to fabricate different wettability pattern surfaces on curve surface of copper tubes. The pattern designs including single wedge with angle 8° or 14°, and double wedges with angle 8° are tested in condensation heat transfer experiments and compare with superhydrophobic and superhydrophilic copper tubes, as well as unmodified copper tube. Experimental results show that condensation heat transfer efficiency and condensation water collection of the copper tubes with double wedge gradient surface of 8° are the best among all designs. Compared with unmodified copper tube, condensation heat transfer efficiency of double wedge gradient surface of 8° can improve 28 %. Experiments also show condensation droplets moving at a higher speed and faster water collection for the copper tube with double wedge gradient surface of 8°.

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