圖型化親疏水表面於強制對流冷凝熱傳增益研究

Enhancement of condensation heat transfer using patterned surfaces in force convection flow

黃昱陽(Yu-Yang Huang)

指導教授 ： 劉耀先

國立交通大學/工學院/機械工程系所/碩士(2018年)

摘要

本研究主要探討親疏水表面對於垂直平板冷凝熱傳的影響，設計不同親疏水圖型化表面於風速0.5-4m/s，環境相對濕度40%、60%、85%下進行測試，本研究測試(1)垂直親水排水道兩側為對稱之親疏水混合排水道，兩側排水道互相平行且傾斜60°之親疏水結構、(2)垂直親水排水道兩側為對稱之排水道，兩側排水道為親水漸縮、疏水漸擴結構、(3)將(2)結構尺寸縮小、(4)將(3)兩側排水道改為親水漸擴、疏水漸縮、(5)星型親水結構、(6)改良星型結構。其親水結構為純銅，接觸角為73°，疏水結構為乙基九氟丁基醚，接觸角為117°。將上述之結構與純疏水及純親水表面做比較，探討其結構對熱對流係數的影響，同時並以高速攝影機記錄其冷凝現象，分析親疏水結構上的液滴移動機制。結果顯示，在親疏水混合的表面，其熱傳表現均優於單一表面，主要原因為表面張力梯度促使液滴移動，使液滴快速滑落，增加其再冷凝頻率，藉由潛熱帶走更多熱量。在本次實驗中，小尺寸親水漸縮結構(3)以及增加親水排水道之改良型星形結構(6)與純親水表面相比提升到了30%。因此在親疏水混合表面之冷凝熱傳中，小尺寸之親疏水結構以及親水排水道的設計為一改善熱傳表現之關鍵因素。

關鍵字

親水 ； 疏水 ； 冷凝熱傳 ； 表面張力

並列摘要

An experiment is performed to study the condensation heat transfer on vertical copper plate in force convection flow. Current study proposes several hydrophobic/hydrophilic hybrid patterns. The inlet condition has three different relative humidity levels, 85%, 60% and 40%. The inlet velocity is changed from 0.5 to 4m/s. The research designs include: (1) symmetrical parallel drainage channels between the main drainage channel. The angle of parallel channel is 60°; (2) symmetrical drainage channels between the main drainage channel. However, the symmetrical drainage channels is convergent in hydrophilic zone and divergent in hydrophobic zone; (3) reduced channel size from (2) pattern; (4)modify the symmetrical drainage channels in (3) with divergent hydrophilic and convergent hydrophobic zones; (5) the star-shaped hydrophilic pattern; (6)Modified star-shaped pattern. The hydrophilic surface is copper with a contact angle of 73°. The hydrophobic zone is coated by ethyl nonafluorobutyl ether with a contact angle of 117°. The results are compared with the hydrophilic and hydrophobic surfaces, and the effect of hybrid pattern on the condensation heat transfer coefficient is investigated. The condensation phenomena is recorded by the high speed camera. The result shows that the hybrid surface is better than the hydrophilic and hydrophobic surface. The surface tension moves the droplets and promotes condensation. Compared to the typical hydrophilic surface, the increase of heat transfer coefficient of the small size pattern (3) and the modified star-shaped pattern(6), is 30% which is highest in all of the pattern. Therefore, the small size of hybrid pattern and hydrophilic drainage channel is beneficial for condensation heat transfer.

並列關鍵字

hydrophilic ； hydrophobic ； condensation heat transfer ； surface tension

參考文獻

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