本文前段所研究單元為，單行程與雙行程交流系統在薄膜透析中加入外回流裝置的影響，其中雙行程中為透餘相取雙通道並分為A-B與B-A兩種。在回流操作的影響下，試著增加流體速度克服因為回流時而與入口進料混合而降低了質傳驅動力(濃度的不同)，並考慮能得到多少的改善現象。後段的薄膜萃取中，同樣是在較大的進料體積流率或較高的進料濃度下可得到改善的現象，這些都可在理論中完整驗證出來。在薄膜萃取雙行程部份為透餘相與透析相皆為雙通道與透析系統中雙行程部分只有透餘相雙通道有所區別。在單行程與雙行程兩種系統比較上，單行程回流質傳已可達到改善現象，而在同樣條件下的雙行程系統中，雙行程模式可更提供流體速度的增加，使雙行程系統能比單行程系統更提高了質傳效果。結論為在此兩種理論研究結果可證明提高濃度、提高兩相體積流率皆能有效地提高質傳效率。 The effect of external recycle on membrane dialysis with single pass in both phases or with double pass in the retentate phase, operated under cross flow was investigated. Considerable improvement is obtainable by using recycle operation to create the describable effect of increasing the fluid velocity, which overcomes the undesirable effect of decreasing the mass-transfer driving force (concentration difference) due to the remixing at the inlet. Theoretical predictions were also carried out for membrane extraction with double pass in both phase. The performance is further improved for higher input volume flow rate, or high inlet concentration. In contrast to a single-pass module, improvement in mass transfer is achievable for some double-pass membrane extraction providing the increase of fluid velocity.
