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    題名: 非對稱管壁熱通量之迴流型二行程平板式熱交換器的熱傳之研究
    其他題名: The recycle effect on double-pass parallel-plate heat exchangers with asymmetric wall fluxes
    作者: 陳衛樽;Chen, Wei-zun
    貢獻者: 淡江大學化學工程與材料工程學系碩士班
    何啟東;Ho, Chii-dong
    關鍵詞: 共軛格拉茲問題;迴流;正交性質;平板熱交換器;非對稱熱通量;Conjugated Graetz problem;External Recycle;Orthogonal expansion techniques;Parallel-plate heat exchangers;Asymmetric wall fluxes
    日期: 2008
    上傳時間: 2010-01-11 05:46:09 (UTC+8)
    摘要: 本研究是設計於兩平行板間加裝一可忽略熱阻之隔板並加入迴流裝置,使之於板壁為非對稱熱量通量下,具迴流之二行程平板型熱交換器。此系統以分離變數法(separation of variables)及重疊理論(superposition method),且利用正交展開法(orthogonal expansion technique) ,求得板壁於非對稱熱流通量下,兩平板間流體的溫度分佈與平均納塞數 (Nusselt number)。此外,同時亦探討迴流效應對平板式質量交換器之熱傳效率的影響,並將其熱量傳送效率之改善與單行程系統及二行程隔板絕熱層作比較。
    熱傳效率主要是受到兩種競爭效應的影響:預混效應以及滯留時間,由結果顯示本研究主要探討不同參數即隔板位置、熱量通量變化、迴流比之大小及格拉茲數對二行程熱交換器之影響;此外加入迴流系統對壁上溫度之均勻度提升,隔板位置與格拉茲數之改變皆為影響流體於通道內滯留時間,這些操作參數皆為造成熱傳效率改變,並與單行程及隔板位置絕熱層作比較,藉此得出非對稱二行程熱交換器之最佳操作設計。
    The new device of parallel-plate heat exchangers with external recycle under asymmetric wall fluxes has been developed theoretically. This system belongs to the conjugated Graetz problem and the analytical solution has been obtained by using the superposition method. The theoretical predictions of heat-transfer efficiency enhancement in double-pass parallel-plate heat exchangers were represented graphically and compared with those in single-pass devices (without an impermeable plate inserted and without recycle) and double-pass devices with an insulated sheet inserted. The theoretical results show that the heat transfer efficiency of parallel-plate heat exchangers under asymmetric wall fluxes increases with increasing the Graetz numbers. The influences of the impermeable location, heat flux ratio and recycle ratio on the heat-transfer efficiency enhancement are also discussed in this study. The power consumption increment caused by the double-pass design and external recycle has also been delineated.
    顯示於類別:[化學工程與材料工程學系暨研究所] 學位論文

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