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，薄膜蒸餾因模組通道限制，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)於模組之進料側增加螺旋型檔板之設計來增加流速以及總通道長度，以求有效改善系統進料側離開系統後之殘於能量，並歸納出一經驗公式，描述此型式的螺旋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，套管型與螺旋通道型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7.61 %，而本研究設定螺旋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39.5%的增益。本研究以操作在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 the DCMD module winding a spiral wire within the annulus of the concentric circular tube was investigated theoretically and experimentally in aiming to increase the pure water productivity in saline water desalination. The hot sea water stream flowing through the annulus of a concentric circular tube, which a tight fitting spiral wire in a small annular spacing is inserted, could enhance the improvement of device performance. The purposes of this study are (1) to develop the heat-transfer coefficient correlation for the spiral wire channel; (2) to develop a one-dimensional mathematical model and propose a general numerical method for predicting pure water productivity of DCMD systems; (3) to study the effects of various operation parameters including the inlet fluid temperatures, volumetric flow rate spiral wire pitch on the pure water productivity improvement. The correlated equation of estimating heat-transfer coefficient for the wire helix by using spiral flow channel was obtained, and the results show that the agreement between the experimental results and the theoretical predictions are fairly good. The new design of DCMD module winding a spiral wire within the annulus of the concentric circular tube can effectively enhance the mass flux, among the operating conditions set in this study, up to 39.5% of the gain.
