Countercurrent exchange

About: Countercurrent exchange is a research topic. Over the lifetime, 2255 publications have been published within this topic receiving 28687 citations. The topic is also known as: Countercurrent exchange.

Condensed steam source heat pump driven multi-effect horizontal pipe falling film distillation column

Abstract: The invention provides a condensed steam source heat pump driven multi-effect horizontal pipe falling film distillation column. A condensed steam source heat pump, heat pipe heat exchange, a horizontal pipe falling film and multi-effect distillation are integrated in a system, and the distillation column is a transboundary product of the heat pump industry, the heat exchange industry and the distillation industry. Last-effect secondary steam condensation latent heat is directly recycled through the condensed steam source heat pump, and it is achieved that a condenser independently provides a heat source needed by first-effect distillation. By means of open-type multi-level heat pipe overlaying, the distillation process of countercurrent flow heat exchange, the horizontal pipe falling film and single-column multiple effects is achieved, and the secondary steam condensation latent heat is utilized effect by effect. Integrated design of the condenser, a multi-effect horizontal pipe falling film distillation column and an evaporator is achieved. The multi-effect horizontal pipe falling film distillation process driven by the condensed steam source heat pump is achieved.

Flux enhancement in crossflow membrane filtration: fouling and it's minimization by flow reversal

Abstract: Fouling problems are perhaps the single most important reason for relatively slow acceptance of ultrafiltration in many areas of chemical and biological processing. To overcome the losses in permeate flux associated with concentration polarization and fouling in cross flow membrane filtration, we investigated the concept of flow reversal as a method to enhance membrane flux in ultrafiltration. Conceptually, flow reversal prevents the formation of stable hydrodynamic and concentration boundary layers at or near the membrane surface. Further more, periodic reversal of the flow direction of the feed stream at the membrane surface results in prevention and mitigation of membrane fouling. Consequently, these advantages are expected to enhance membrane flux significantly. A crossflow membrane filtration unit was designed and built to test the concept of periodic flow reversal for flux enhancement. The essential elements of the system include a crossflow hollow fiber membrane module integrated with a two-way valve to direct the feed flow directions. The two-way valve is controlled by a controller-timer for periodic reversal of flow of feed stream. Another important feature of the system is that with changing feed flow direction, the permeate flow direction is also changed to maintain countercurrent feed and permeate flows for enhanced massmore » transfer driving force (concentration difference). Bovine serum albumin (BSA) is a well-studied model solute in membrane filtration known for its fouling and concentration polarization capabilities. Laboratory-scale tests on a hollow-fiber ultrafiltration membrane module using BSA solution as feed show that under flow reversal conditions, the permeate flux is significantly enhanced when compared with the conventional unidirectional flow. The flux enhancement is dramatic (by an order of magnitude) with increased feed concentration and operating transmembrane pressure.« less