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    Title: 平板型多效直接接觸式薄膜蒸餾系統之理論與實驗研究
    Other Titles: Theoretical and experimental studies of the multi-effect direct contact membrane distillation with fins attached in flow channels
    Authors: 蔡鎮皓;Tsai, Cheng-Hao
    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: 薄膜蒸餾;透膜通量;擾流增益因子;溫度極化;Membrane distillation;trans-membrane flux increment;eddy promoter;temperature polarization
    Date: 2013
    Issue Date: 2014-01-23 14:28:24 (UTC+8)
    Abstract: 薄膜蒸餾海水淡化用來製造純水提供民生及工業使用,因其優點特色為具有裝置簡潔、低成本、可模組化、高介面面積等,為近來廣受重視的一種技術。然而,薄膜蒸餾因主流區與薄膜表面溫度存在所謂的溫度極化現象,對於系統產能有相當顯著的影響,此現象越明顯則產能相對低落。
    本研究針對薄膜蒸餾之主要設備進行效率改善的研究,目的為:(1)將系統改善為多效式操作以增加薄膜接觸面積進而增加產量;(2)於薄膜兩側增加碳纖維板之設計來增加流速以及擾流增益因子(Eddy promoter),以求有效改善系統內部的溫度極化現象進而提升系統產能,並歸納出一經驗公式,描述此型式的擾流增益進因子對於通道內部熱對流效應的影響;(3)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,平板型多效直接接觸式薄膜蒸餾系統之理論值與實驗值的相對誤差總平均為7.11 %,而本研究設定新型擾流增益因子能夠有效的提升系統透膜通量,最高可達到單位面積的21 %的增益。本研究以操作在多通道與低體積流率之設備為主,除了有效利用通道內熱側流體以降低操作成本外,經由改善後的設計可提升設備效能並得到增加透膜通量總產量的效果。
    A new design of direct contact membrane distillation (DCMD) using the multi-effect DCMD device for enhancement of heat transfer was proposed for increasing the pure water productivity in saline water desalination. It can be performed at middle temperature operation (about 45 °C to 60 °C) of hot inlet stream associated with a constant temperature of cold stream inlet. The double-flow device of DCMD is the basic and reference designs for constructing the multi-effect DCMD device. The existence of temperature gradient in a DCMD means that the membrane surface temperatures always contrast with bulk temperatures which called temperature polarization, may cause a considerable heat loss. Attempts to reduce the effect of temperature polarization were made implementing turbulence promoters to improve the flow characteristic. Experimental study has demonstrated its feasibility, and a considerable performance enhancement was obtained for the experimental system. The purposes of this study are (1) to develop the multi-effect DCMD in order to increase pure water productivity; (2) to develop the heat transfer correlation for the carbon fiber on both side of the membrane in both channels (3) to develop a one-dimensional mathematical model, propose a general numerical method for solving this model to predict pure water productivity and study the effect of temperature distributions and polarization on the pure water productivity improvement of the membrane distillation systems. The correlation is expressed as eddy promoter and can be used for predicting the heat transfer coefficient for attaching fins in flow channels. The results show that the agreement of the theoretical predictions with the experimental results is fairly good. The new design of eddy promoter can effectively enhance the mass flux, among the operating conditions set in this study, up to 21% of the gain.
    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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