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.

A two-phase computational fluid dynamics model for ozone tank design and troubleshooting in water treatment

Abstract: A computational fluid dynamics (CFD) tool was employed to design and study ozone contactors The emphasis was to achieve the desired flow distribution The Eulerian-Eulerian multiphase model was used with the standard k-ϵ turbulent model The water surface was slip wall boundary and was specified as a sink to remove ozone bubbles For a single-column contactor with side entry, the flow pattern was found to be crucially dependent on both the direction and magnitude of the entry velocity from the inlet pipe It was difficult to achieve uniform gas concentration over the contactor volume In a multicompartment contactor, the countercurrent flow resulted in a mixed flow condition and the mixing increased with a higher gas rate For the cocurrent flow, water was accelerated by the gas and the plug flow pattern was achieved The flow distribution in each compartment can be significantly different even though the overall residence time distribution curves are similar

Countercurrent regeneration process

Abstract: A method of regenerating an ion exchanger which is used to treat a solution introduced to the ion exchanger in a downward charging direction. The ion exchanger comprises a non-constrained bed of ion exchange material in the form of ion exchange granules and has a concentration profile through the ion exchange material after the solution has been introduced to the ion exchanger in the charging direction. The method in one embodiment comprises passing a regenerating solution upwardly through the non-constrained bed of ion exchange material in an intermittent pulsed flow comprising a pulse or up flow of regenerating solution, a subsequent non-flow pause time, followed by a down flow pulse in a direction opposite to the up flow. The duration and velocity of the pulse or up flow of regenerating solution is sufficient to hydrodynamically lift the ion exchange granules a controlled distance through all of the ion exchange granules without causing significant mixing of ion exchange granules between different layers of the ion exchange material. The duration of the subsequent non-flow pause time being of short duration to allow for some perceptible settling of the ion exchange granules, with the down flow pulse being sufficient to reduce the sedimentation time of the ion exchange granules to a fraction of the normal settling time for the granules in the absence of the down flow pulse.

Isoparaffin-n-paraffin separation process

Abstract: NORMAL PARAFFINS ARE SEPARATED FROM ADMIXTURE WITH NON-NORMAL PARAFFINS IN THE VAPOR PHASE AT SUPER-ATMOSPHERIC PRESSURE USING A FIXED ADSORPTION BED CONTAINING A 5-A. ZEOLITIC MOLECULAR SIEVE ADSORBENT. HIGH PURITY NORMALS ARE OBTAINED IF THE ADSORPTION STROKE IS CONTINUED UNTIL THE STOICHIOMETRIC POINT OF THE NORMALS MASS TRANSFER ZONE HAS TRAVERSED TO BETWEEN 85 AND 97 PERCENT OF THE BED LENGTH AND THEREAFTER TWO COUNTERCURRENT PURGE STAGES USING A NON-SORBABLE PERMANENT GAS ARE EMPLOYED, THE FIRST BEING ONLY SUFFICIENT TO FLUSH THE VAPORS FROM THE BED VOID SPACE.

Mechanism and Effects of Predominant Parameters Regarding Limitation of Falling Water in Vertical Countercurrent Two-Phase Flow

Abstract: In this study, an investigation was carried out to clarify the mechanism of countercurrent flow limitation (CCFL) or flooding, that is, limitations in the falling water mass flux in countercurrent two-phase flow in vertical channels, and to identify the effects of predominant parameters regarding CCFL, adopting the criterion that the CCFL condition be given by an envelope of momentum equation applied for the entire length of the channel with respect to any void fraction. As a result, it was found that the analytical model proposed could adequately predict all existing experimental results investigated in this study. In the channel configuration, circular, rectangular, and annular or planar channels, channel dimensions of diameter, gap size, width or circumference, and length, interfacial and wall friction, water injection mode, and inlet water subcooling were dominant parameters. Therefore, both the mechanism and the quantitative effects of CCFL have been identified.

Research test dialyzer system

Abstract: A test unit and a method for testing membranes, membrane support systems and solution diffusivities for parallel and countercurrent flow of liquids, temperature effect on liquids, pressure effect on liquids with respect to a positive pressure and to a negative pressure, for two and three liquid systems, and for use under sterile and nonsterile conditions.