多層U形微流道內排水效率與氣泡傳輸與添加界面活性劑之研究

Abstract

為了解決燃料電池蜿蜒流道積水的問題，本實驗設計四層蜿蜒流道，並加上細分支，研究各種流體在流道中的穩定性、濕潤性以及排出率進行分析。並設計入口處，分析十字聚焦結構，與T形結構的不同，發現十字聚焦結構，能有效地產生週期穩定，大小相同的氣泡；也分析了濕潤性與非濕潤性對於排水的影響，發現濕潤性能夠有效排水，並且把空氣留住，不會從分支流出，可以達到排水集氣的效果。並用capillary number(Ca)來判斷流道的濕潤性，實驗也發現一般的自然界純物質，例如：純水、純甘油、純酒精都能完全的結合，但對於只要添加界面活性劑氣泡就完全無法結合，所以添加界面活性劑就有排水效率的極限。最後用Ca和排出量作圖，Ca越大排出量會越多。 最後，由實驗結果顯示，設計四層分支流道，可以排出90%以上的流體，並且把氣體留在流道中，可以解決氫氧燃料電池積水的問題，並在流道中添加界面活性劑可以降低表面張力，提升流道的濕潤性，以利於低流速也可達到濕潤的效果，藉由此流道排水，可以提升燃料電池的效率。

In order to solve the problem that water remains in multi-serpentine channel, the present study performs a multi-serpentine channel with drainage branches, and various fluids were applied to investigate effects that different fluid properties bring. With applications of T-junction and flow focusing geometry, bubbles were produced to analyze the stability, wettability and size of bubbles. We used Ca-We diagram to categorize bubble generation regimes. The diagram shows that the transition of boundary between wetting and non-wetting bubbles occurs at about Ca=0.006. In the results of the research, the drainage rate was increased as the Ca increased. Finally, the experimental results show the channel could drain more than 90% of fluid. Furthermore, the gas could be maintained in the flow channel, thus the problems of hydrogen fuel cells could be solved. Adding surfactant in the fluids could reduce the surface tension, and would enhance the wettability. Thus wetting could be achieved in low flow rates condition, and the efficiency of fuel cell would be improved.