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.

Heat exchanger structure for reducing accumulation of liquid and freezing

Abstract: The invention relates to a method for reducing accumulation of liquid and freezing in a plate type countercurrent heat exchanger (100) comprising a stack of heat transfer plates (102). There is also provided a plate type countercurrent heat exchanger (100) comprising a stack of heat transfer plates (102) forming a primary flow channels for a first flow (116) of heat exchange gas and a secondary flow channels for a second flow (118) of heat exchange gas. The stack of heat transfer plates comprise a channelling section (138) in which the primary flow channels and the secondary flow channels are located. The channelling section (138) of the heat transfer plates (102) comprises formations which form ridges and grooves the direction of which is at an angle with respect to the direction of flows (116, 118) of the heat exchange gases in the primary flow channels and the secondary flow channels. In some embodiments the direction of ridges and grooves is perpendicular to the direction of flows. In some embodiments the distance between two adjacent plates in the stack is substantially constant at the channelling section (138). The structure of the heat exchanger plates according to the present invention reduces the risk of liquid building up inside the heat exchanger and hence reduces the risk of forming ice on the surfaces of the heat exchanger plates. Therefore, flowing of gases (e.g. air) inside the heat exchanger is also improved.

Numerical model for the investigation of countercurrent chromatography.

Abstract: A numerical model is developed to describe the separation process of countercurrent chromatography (CCC) in this work. The theory of countercurrent extraction table (TCCET) is first proposed to calculate concentration distributions of chemical components in the CCC, which is essential for a numerical model to describe the dynamic equilibrium of mass transfer. According to the theory of countercurrent extraction, the concentration in chromatography obeys binomial distribution, while the outflow from the n-th stage is a negative binomial distribution. As a result of the central limit theorem, they will obey normal distribution for sufficiently large n. Row-stage ratio (R(RS)) is then defined to determine the K value or retention time because it has a linear relationship to K value and retention time. The stage for a certain K value can be subsequently obtained with a very simple form, n(k)=1/(2piq(k)X(2)(k, max)), which can be calculated from the peak height obtained from experiments. Finally, the actual stage for a separation chromatogram can be acquired with using this simple expression. The agreement between theoretic and experimental results is quite satisfactory in the normal-phase and reversed-phase elution mode.

Experimental Study of the Flooding and Appearance of a Bubble Bed on Top of a Countercurrent Packed-Bed Column

Abstract: This paper presents an experimental study of the countercurrent packed-bed column in the course of flooding and above the flooding point when the column operates as a packed bed and a bubble bed in...

Countercurrent liquid-solids contact process

Abstract: A METHOD IS PROVIDED FOR THE CONTINUOUS COUNTERCURRENT CONTACT OF A SOLID SUCH AS AN LON-EXCHANGE RESIN, WITH A LIQUID WHEREIN THE LIQUID IS CONTACTED STEPWISE WITH AN INCREASINGLY FRESH RESIN THEREBY INSURING MAXIMUM IONEXCHANGE EFFICIENCY. D R A W I N G

Influence of fluid properties on the hydrodynamics and operability of a countercurrent supercritical packed column

Abstract: The hydrodynamic operability and the influence of fluid properties on hydrodynamics under supercritical conditions were investigated in a 38 mm diameter column packed with ¼” Dixon rings. The column was operated using 100 cSt and 200 cSt Poly[dimethylsiloxane] (PDMS), with supercritical CO2 at 14 MPa and 333 K, 328 K and 323 K respectively. The pressure drop, liquid hold-up, mass flow and mass fractions were measured. The column operability limits were determined for both systems over a range of liquid and supercritical fluid flow rates using the measured data. Three distinct types of inoperability were identified, namely liquid layer flooding, bubble column flooding and excessive entrainment. It was found that liquid hold-up and pressure drop are not reliable indicators of operability in supercritical systems. Further, no observable loading operating regime was found, with the column only operating in the pre-loading or inoperable (flooded/entrained) regimes. The influence of the density and dynamic viscosity on hydrodynamics was found to be complex, yet significant. Small changes in temperature caused substantial changes in fluid properties, having a significant impact on column operability. Column operability range reduced with an increase in liquid viscosity and SF density. Finally, the data are compared to available models.