關於平板薄膜透析操作之質傳問題在理論上可以類比於平板式熱交換器的熱傳方式。本文主要探討回流裝置的加入對於平板式薄膜透析系統的改善情形，薄膜透析的外回流效益是在並流的單行程雙相及雙行程的透餘相模式中研究下運作。藉由回流操作產生因流速增加所得到的可期效益中大量的效能增進是可以做到的。由於進料的再混合，回流操作克服了減少質量傳送驅動力(濃度差)會產生的負面效益。回流可以增加薄膜透析的效能，特別是對於具有大進料體積流率的流體，或者是高濃度的進料溶液。再者，雙行程操作比單行程更有效益，因為流速的增加會使質量傳送係數增加。 The effect of external recycle on the membrane dialysis with single pass in both phases on double pass in retentate phase, under parallel flow was investigated. Considerable improvement in performance is obtainable by using recycle operation to create the desirable effect of increasing the fluid velocity, which overcomes the undesirable effect of decreasing the concentration difference for mass-transfer due to the remixing at inlet. The recycle can enhance the performance of membrane dialysis, especially for higher volume flow rate or higher concentration of inlet solution. Further moer, double pass operation is more effective than the single pass because of the increase in fluid velocity, resulting in increasing the mass-transfer coefficient.
