迴流效應於非對稱質量通量之二行程平板式 層狀逆流型質量交換器效率改善之研究

Performance Improvement on Double-Pass Parallel-Plate Laminar Counterflow Mass Exchangers with External Recycle and Asymmetric Wall Fluxes

李博鈞(Po-Chun Lee)

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(2008年)

https://doi.org/10.6846/TKU.2008.00707

摘要

為了求解非固定質量通量下伴隨迴流裝置之平板型質量交換器的共軛格拉茲問題，本研究使用分離變數法(separation of variables)及重疊理論(superposition method)，並在求解過程中利用正交展開法(orthogonal expansion technique)，得其壁上濃度、平均濃度分佈及平均謝塢數(Sherwood number)。此外於不同迴流裝置下，亦探討改變操作參數時對質傳效率的影響，並與單行程系統及中間加裝不可滲透薄膜之系統作比較。
結果顯示，預混效應、滯留時間及孔隙度皆是影響質傳效率的重要因素，此外質量通量與薄膜位置的相互關係亦會對系統有顯著的影響。當質傳格拉茲數較大時，不僅可使壁上濃度分佈均勻而有利於材料的選擇，也可使質傳效率有明顯的改善。最後在本文中，迴流系統因薄膜位置與迴流比的變化所增加的能源消耗也將與單行程系統相比，藉此得出二行程平板式質量交換器之最佳操作與設計。

關鍵字

共軛格拉茲問題 ； 迴流 ； 平板型質量交換器 ； 質傳改善率 ； 非對稱壁通量

並列摘要

A new device of double-pass mass exchanger under asymmetric wall fluxes is to divide a parallel-plate channel by inserting a permeable barrier into two subchannels. The recycle effect was introduced to the double-pass mass exchangers under asymmetric wall fluxes to improve the mass transfer efficiency. The theoretical formulation of such conjugated Graetz problems were developed by making mass balance and the analytical solutions were obtained by using the superposition method of an asymptotic solution and a homogeneous solution. The theoretical predictions of the double pass mass exchanger with external recycle were compared with those in single-pass devices and double-pass devices with an impermeable sheet inserted under the same working dimensions. The considerable mass-transfer efficiency improvement is obtainable for large mass-transfer Graetz number. The influences of the permeable-barrier location and recycle ratio on the mass transfer efficiency enhancement and the power consumption increment are also discussed in this study.

並列關鍵字

conjugated Graetz problem ； external recycle ； parallel-plate mass exchanger ； performance improvement ； asymmetric wall fluxes

參考文獻

35. C.D. Ho, H.M. Yeh, J.W. Tu, An analytical study of parallel-plate mass exchangers with permeable barriers inserted for multi-pass operations, Journal of the Chinese Institute of Chemical Engineers 35 (5) (2004) 285-297.

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