雙件式氣隔型薄膜蒸餾系統於海水淡化之效率提升

Device Performance Improvement of Double-unit Air Gap Membrane Distillation Module for Seawater Desalination

陳禹安(Yu-An Chen)

指導教授 ： 何啟東

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2018年)

https://doi.org/10.6846/TKU.2018.00489

摘要

薄膜蒸餾技術運用於海水淡化，優點為有效利用低溫熱源、可操作於常壓下及設備精簡，因此能使成本低廉，故成為十分具有吸引力的開發技術。本研究之氣隔式薄膜蒸餾系統是利用多孔性疏水膜作為介質，利用薄膜兩側之流體溫度差異導致飽和蒸汽壓不同，驅動水蒸氣穿透薄膜及氣隔層，在金屬板上冷凝，達到分離之目的。研究之操作為3.5wt%鹽水之純化，操作變因為流體進口溫度、體積流率，而設計變數是以波浪型碳纖維板當作紊流促進因子，結合數學模型理論，探討系統溫度極化之改善。
本研究針對氣隔式薄膜蒸餾系統之效率改善主要有兩大方向：
(1)薄膜之熱流層側加裝波浪型碳纖維板作為新型紊流促進因子(eddy promoter)，使流體流動時產生擾流狀態，增加通道內部之熱對流效應，改善溫度極化現象，有效提升系統產能，並歸納出新型納賽數經驗公式。
(2)建立一維數學模型，探討系統之熱量傳送及質量傳送機制及數學解析程序，透過實驗結果分析驗證經驗公式之適用性，並分析在不同設計參數及操作條件下之溫度極化係數、透膜通量增益百分比及水力損耗增加百分比。
本研究之操作型態為雙件式氣隔型薄膜蒸餾系統，有效利用熱側之流體，降低操作成本，且研究結果顯示，加裝波浪型碳纖維板作為新型紊流促進因子能有效提升系統之透膜通量，其實驗值與理論值相對誤差總平均為5.39 %，而最高之單位面積增益量為16.81 %。

關鍵字

氣隔式薄膜蒸餾系統 ； 透膜通量 ； 碳纖維板 ； 溫度極化

並列摘要

The modeling equations for predicting distillate flux in a double-unit air gap membrane distillation (AGMD) module with inserting corrugated carbon-fiber open slots were developed theoretically and experimentally. The double-unit design gives a more compact module with an increase in pure water productivity for desalination applications. The operation of AGMD module with inserting carbon fiber spacers results in a higher permeate flux as compared to that of the module with an empty channel. The corrugated carbon-fiber open slots acting as an eddy promoter could not only strengthen the membrane stability for preventing from vibration but also enhance the distillate flux with lessening temperature polarization effect. The correlated expression of Nusselt number for inserting corrugated carbon-fiber open slots was formulated incorporating with experimental data, and thus, the prediction of the heat transfer coefficient for the AGMD module was obtained. The effects of volumetric flow rate and fluid inlet temperature on the permeate flux were also delineated with considering the power consumption increment due to inserting corrugated carbon-fiber open slots. The good agreement between the experimental results and theoretical predictions was accomplished.

並列關鍵字

Air gap membrane distillation ； Permeate flux ； Carbon-fiber spacers ； Temperature polarization

參考文獻

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