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.

Modeling of Processes of Gas Cooling by Contact with a Liquid and Updating of Column Apparatuses

Abstract: The process of gas cooling with a liquid in a countercurrent packed column (scrubber), where the phases are in direct contact, is described. The system of differential equations for heat transfer in gas and liquid phases and moisture mass transfer is given. Equations for determining the fields of gas enthalpy distribution, liquid temperature, moisture content in the gas along the packed bed height are derived through transition to a cellular model. The adequacy of the proposed equations is validated in practice. The packed column is updated, which involved replacement of plates by packings produced by OOO IVTs Inzhekhim (EPC Chemical Engineering LLC), which enhanced the efficiency of pyrogas cooling with water in ethylene production.

Computer Simulation of Zirconium-Hafnium Separation by Countercurrent Extraction

Abstract: In carrying out research and development on an improved method for production of reactor-grade zirconium oxide, the Bureau of Mines has prepared a computer program capable of accurately predicting the stage-by-stage performance of a multistage countercurrent solvent extraction system for separation of zirconium from hafnium using a tertiary amine extractant. The results were used to plan laboratory experiments using a multistage countercurrent mixer-settler unit. The number of extractor stages, number of scrubber stages, feed solution concentrations, scrubber solution concentration, feed flow, scrubber flow, and organic-phase flow are the significant variables. The computer simulation indicates the effects of changes in the pertinent variables and makes it possible to locate the best combination of variables without a prohibitively large number of time-consuming experiments.

A Mechanistic Model for Countercurrent Steam-Water Flow

Abstract: A one-dimensional model has been developed to describe the flow behavior of a liquid film draining down a heated wall, in the presence of countercurrent vapor flow. The effects of nonequilibrium void generation at the walls and condensation of countercurrent vapor on the penetrating liquid film interface, as well as on the bypassed liquid, have been considered. The momentum exchange is described by a correlation, assumed to apply at the entrance region, where the amount of liquid film flow is limited by the net vapor upflow. Theoretical predictions were compared with over 600 test results, obtained in 1/15- and 2/15-scale models of a PWR downcomer, over a wide range of test parameters. The comparisons exhibit a fairly good agreement.

Effectiveness-NTU Relations for Heat Exchangers With Streams Having Significant Kinetic Energy Variation

Abstract: Effectiveness-NTU equations are derived for counter and parallel-flow heat exchangers with fluids having high velocities. In this case, the change in the kinetic energy occurring within the heat exchanger will significantly affect the temperature profiles. The effectiveness is found to depend on the usual non-dimensional variable that compare the heat exchanger conductance to the hot- and cold-side capacity rates and on four additional nondimensional quantities that reflect the magnitude and distribution of the kinetic energy on the hot and cold-sides of the heat exchanger The governing differential equations are derived, nondimensionalized, and solved analytically for the case of an exponentially distributed kinetic energy. Graphical solutions are presented and interpreted for several cases. The solutions are applied to a particular case involving high velocities within a counter-flow heat exchanger used to produce cryogenic temperatures.