本研究目的為在銅管外壁設計不同混合潤濕性圖形表面改質，利用親疏水區域之特性，使冷凝液滴形成並驅動結合成大液滴離開熱交換冷凝器表面，增強銅管冷凝熱傳效率，以提升冷凝熱交換器內部銅管整體冷凝熱傳性能。表面改質乃利用網印製程，此方法不僅可降低成本也可以節省微影蝕刻的時間。本研究製作之五種銅管混合潤濕性圖形：條狀圖形、疏水圓點、親水圓點、三角陣列及魚骨圖形，梯度表面的親水區設計主要寬度皆為0.5 mm，變化疏水區的寬度並進行不同銅管表面冷凝熱傳實驗及觀察表面液滴滯留現象。與未經改質的純銅管與全疏水銅管作熱傳性能比較，結果發現在固定實驗條件之下，疏水區寬度WDWC為0.862 mm， 親水區寬度WFWC為0.5 mm的條狀圖形，在ΔTsub = 5K介於ΔTsub = 15 K時熱傳效果與其他圖形相比較佳，在過冷溫度 ΔTsub = 15 K時可達4.8 kW，效率比純銅管提高了71% 。且較無液滴滯留現象。其他圖案的液滴滯留現象都較為嚴重，在ΔTsub = 5K介於ΔTsub = 15 K時都無較佳表現，圓點圖形及三角陣列圖形需在ΔTsub > 30K才可達到4 kW的熱傳量。在液滴滯留現象方面，條狀圖形的表面較無液滴滯留，具良好的機制驅動液滴並互相結合及快速帶離表面。疏水圓點圖形因小圓點形成的液滴易與親水區的水膜相連接，排水困難。三角陣列圖形的親水楔型能有效驅動液滴，但在楔型與楔型之間產生大量液滴滯留。魚骨圖形則較不易產生液滴滯留的現象。整體來說，本研究製作之條狀圖形表面改質熱傳性能最好，可應用於熱交換冷凝器上。

In order to enhance condensation heat transfer efficiency of a copper tube with fast droplet movement. This research use screen printed surface modification to fabricate different wettability patterns on copper tube. Applying the screen printing technique not only reduce the fabricate cost but also have highly convenient in manufacture. Surface modification can define the area for hydrophobic or hydrophilic. Hydrophobic areas (dropwise condensation areas) can form droplets with high contact angle, then hydrophilic areas (filmwise condensation area) attract the droplets forming a water film, thus it can move the droplet quickly and speed up the condensation. This research designs different copper tube with different patterns, including unmodified pure copper tube, superhydrophobic, strip pattern, hydrophobic dot pattern, hydrophilic dot pattern, triangle array pattern and fishbone pattern. Compared these patterns condensation heat transfer efficiency, all the wettability patterns heat transfer efficiency are better than unmodified pure copper tube, but the strip pattern with hydrophobic width WDWC 0.862mm and hydrophilic width WFWC 0.5mm have the greatest heat flux. At ΔTsub = 16 K, strip pattern heat flux can reach 4.8 kW. Other patterns cannot reach such higher heat flux.
Strip pattern have clearly hydrophobic and hydrophilic area, it won’t let liquid films stuck on the surface. But other patterns, like hydrophobic dot pattern, hydrophilic dot pattern and triangle array pattern easily accumulate droplets on the hydrophilic area, it will decrease the heat transfer efficiency due to the surface cannot form new droplets quickly. In summary, strip pattern have great mechanism to increase the heat flux, it can also applied on the condenser.

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