氣隔式薄膜蒸餾於純水產量提升理論與實驗之研究

氣隔式薄膜蒸餾(air gap membrane distillation)原理乃是利用薄膜兩側的飽和蒸汽壓差為驅動力促使水蒸氣通過薄膜及其氣隔層後，在冷凝板上冷凝，進而達到分離的效果，然而，當薄膜蒸餾發生所謂的溫度極化現象時，其對於系統產能會有相當顯著的影響，此現象越明顯則產能相對低落。本研究針對氣隔式薄膜蒸餾之主要設備進行效率改善的研究，目的為：(1)設計新型紊流促進因子(Eddy promoter)，以有效的改善系統內部之溫度極化現象進而提升系統產能，並歸納出一新型納賽數經驗公式，描述紊流促進因子對於通道內部熱對流效應的影響；(2)藉由一維數學模型針對薄膜蒸餾設備的熱量與質量傳送機制進行研究，配合實驗分析以驗證經驗公式與數學模型的正確性，並探討在不同之設計參數及操作條件對於薄膜蒸餾系統之流體溫度分佈、溫度極化現象、純水透膜通量增加百分率與水力損耗提升百分率的影響。研究結果顯示，平板型氣隔式薄膜蒸餾系統之理論值與實驗值的相對誤差總平均為8.84 %，而新型紊流促進因子能夠有效的提升系統透膜通量，在本研究設定的操作條件之中，最高可達到約10%的增益。

關鍵字

紊流促進因子；薄膜蒸餾；溫度極化；提升透膜通量

並列摘要

The air gap membrane distillation (AGMD) device is a membrane distillation (MD) operation for which air gap between the membrane and the condensation surface in contact with the cold stream. The existence of temperature gradient in a AGMD system means that the membrane surface temperatures always contact with bulk temperatures. Attempts to reduce the effect of temperature polarization were made implementing eddy promoters to improve the flow characteristic. A new design of the parallel-plate AGMD device using roughened-surface flow channel for heat transfer enhancement was proposed to increase the pure water productivity in saline water desalination. The purposes of this study are (1) to develop the heat-transfer coefficient correlation for the roughened-surface channel; (2) to develop a one-dimensional mathematical model and propose a general numerical method for predicting pure water productivity of membrane distillation systems; (3) to study the effect of temperature polarization on the pure water productivity improvement. The correlated equation of estimating heat-transfer coefficient for the eddy promoter by using roughened-surface flow channel was obtained, and the results show that the agreement between the experimental results and the theoretical predictions are fairly good.

並列關鍵字

Eddy promoter ； membrane distillation ； temperature polarization ； trans-membrane flux increment

參考文獻

2.Kalogirou S.A., 2005, Seawater desalination using renewable energy sources, Prog. Energy Combstion Sci., 31, 242-281.

3.Meindersma G.W., Guijt C.M., de Haan A.B., 2006, Desalination and water recycling by air gap membrane distillation, Desalination, 187, 291–301.

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氣隔式薄膜蒸餾於純水產量提升理論與實驗之研究

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