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    Title: 直接接觸式薄膜蒸餾於中空纖維模組之模擬與實驗分析
    Other Titles: Modeling and experimental analysis of direct contact membrane distillation in hollow-fiber modules
    Authors: 楊子瑾;Yang, Tzu-Jing
    Contributors: 淡江大學化學工程與材料工程學系碩士班
    何啟東;Ho, Chii-dong
    Keywords: 直接接觸式薄膜蒸餾;中空纖維模組;解析解;Direct contact membrane distillation;Hollow fiber membrane module;Analytical solution
    Date: 2011
    Issue Date: 2011-12-28 18:49:30 (UTC+8)
    Abstract: 薄膜蒸餾(membrane distillation, MD)為近來廣受重視的一種技術,其特色為具有裝置簡潔、低成本、可模組化、高介面面積等多方面之優勢,直接接觸式薄膜蒸餾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,進而達到分離的效果。
    本研究主要是針對屬於共軛格拉茲問題的薄膜蒸餾系統進行理論分析,利用分離變數法將系統之偏微分方程式化簡為常微分方程式以求解其特徵函數,再使用正交展開法求得出入口之展開係數,配合邊界條件,即可求得系統中之二維溫度分佈式,並針對平板型、套管型與中空纖維型三種不同類型之薄膜蒸餾系統作解析,求出在不同操作之條件下,冷熱兩相之溫度分佈,探討不同操作參數對於純水產率的影響,此外,研究中也推導出系統冷熱兩相之平均溫度分佈、平均納塞數等數學表示式。
    以本論文所推導之理論為基礎,對直接接觸式薄膜蒸餾作討論,發現不論是何種類型之薄膜蒸餾,增加冷熱水流速及提高熱側進口溫度皆可使純水透膜通量增加,在各種溫度下之透膜通量變化也都符合理論預測。此外,由平板式及中空纖維型薄膜蒸餾實驗所得之結果更可以確定本論文所提出的數學模型之正確性。本研究中無須經過費時的實驗即可求出整個薄膜蒸餾系統的平均納塞數,且可得到系統之二維溫度分佈式。
    Membrane distillation is a feasible technology for desalination by utilizing the vapor pressure difference across a hydrophobic membrane via temperature driving force. Potential advantages of membrane distillation over traditional evaporation processes including (1) it is easy to scale-up, (2) possibility of using modules in series, (3) modularity, (4) high level of interface area and low investment, etc.
    The analytical solutions for such conjugated Graetz problems in direct contact membrane distillation systems (DCMD) were obtained by using the separated variable method with an orthogonal expansion technique extended in power series. The effects of operation parameters in three membrane distillation systems, include flat-plate module, circular-tube module and hollow fiber module
    are investigated theoretically, this theoretical predictions were represented graphically with the Graetz number (volumetric flow rate), flow pattern and hot feed inlet temperature as parameters, besides, the temperature profiles and average Nusselt numbers has been examined and reported.
    The analytical results reveal that the initial saline temperature effect in the hot feed stream on the pure water productivity is more significant than hot and cold feed stream flow rate variations. However, a higher flow rate of hot or cold feed stream still has positive effects on producing better pure water productivity in the case when the inlet saline temperature is specified. The experiments in hollow fiber module were carried out in this study to confirm the accuracy of the theoretical results, and the mathematical model derived in the present study can also be applied to other membrane distillation process to estimate the pure water productivity.
    Appears in Collections:[化學工程與材料工程學系暨研究所] 學位論文

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