Analysis of mass transfer in parallel-flow dialyzer with internal recycle for improved performance

• Mass transfer for dialysis can be improved by applying the reflux effect.
• Theoretical analysis of mass transfer in the dialyzer is analogous to heat transfer in heat exchangers.
• Mass transfer resistance is reduced with the increase of fluid velocity by recycling.
• Considerable improvement in mass transfer is achieved, especially for large flow rate and high reflux ratio.

The internal reflux effect on dialysis through the retentate phase of a parallel-flow rectangular module is investigated. Theoretical analysis of mass transfer in the membrane devices with or without recycling is analogous to heat transfer in heat exchangers. In contrast to a device without reflux, considerable mass transfer is achievable if parallel-flow dialyzers are operated with reflux, which provides an increase in fluid velocity, resulting in a reduction in mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration operated under high reflux ratio.