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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.


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Journal ArticleDOI
TL;DR: In this paper, the hydraulic capacity of a countercurrent column with gauze packing was examined at pressures between 8 and 30 MPa and temperatures between 313 and 373 K. A distinctive change in the flooding mechanisms from liquid layer flooding to bubble column flooding was observed at Φ = L/G(ρG/ρL)0.5 = 0.4.
Abstract: The hydraulic capacity of a countercurrent column with gauze packing was examined at pressures between 8 and 30 MPa and temperatures between 313 and 373 K. The systems used were water + carbon dioxide, aqueous surfactant solution + carbon dioxide, and “Toco”, a substance whose physical properties are roughly similar to those of α-Tocopherol + carbon dioxide. A distinctive change in the flooding mechanisms from “liquid layer flooding” to “bubble column flooding” was observed at Φ = L/G(ρG/ρL)0.5 = 0.4. The different liquids, water and “Toco”, showed the same flooding behavior, indicating that the influence of the density on the flooding behavior prevails over the influence of any other physical property of the liquid. The foamability of the surfactant solution decreased significantly with increasing pressureits influence on the flooding behavior could not be proved. The liquid holdup ranged between 2% and 6%. The dry pressure drop adhered to the Ergun equation.

30 citations

Journal ArticleDOI
TL;DR: It was found that a good reaction could be obtained in the liquid continuous mode, but little separation, while in the gas continuous mode there was little reaction but good separation, and the ICRS to the ethanol‐from‐whey‐lactose fermentation system has been investigated.
Abstract: The simultaneous separation of volatile fermentation products from product-inhibited fermentations can greatly increase the productivity of a bioreactor by reducing the product concentration in the bioreactor, as well as concentrating the product in an output stream free of cells, substrate, or other feed impurities. The Immobilized Cell Reactor-Separator (ICRS) consists of two column reactors: a cocurrent gas-liquid "enricher" followed by a countercurrent "stripper" The columns are four-phase tubular reactors consisting of (1) an inert gas phase, (2) the liquid fermentation broth, (3) the solid column internal packing, and (4) the immobilized biological catalyst or cells. The application of the ICRS to the ethanol-from-whey-lactose fermentation system has been investigated. Operation in the liquid continuous or bubble flow regime allows a high liquid holdup in the reactor and consequent long and controllable liquid residence time but results in a high gas phase pressure drop over the length of the reactor and low gas flow rates. Operation in the gas continuous regime gives high gas flow rates and low pressure drop but also results in short liquid residence time and incomplete column wetting at low liquid loading rates using conventional gas-liquid column packings. Using cells absorbed to conventional ceramic column packing (0.25-in. Intalox saddles), it was found that a good reaction could be obtained in the liquid continuous mode, but little separation, while in the gas continuous mode there was little reaction but good separation. Using cells sorbed to an absorbant matrix allowed operation in the gas continuous regime with a liquid holdup of up to 30% of the total reactor volume. Good reaction rates and product separation were obtained using this matrix. High reaction rates were obtained due to high density cell loading in the reactor. A dry cell density of up to 92 g/L reactor was obtained in the enricher. The enricher ethanol productivity ranged from 50 to 160 g/L h while the stripper productivity varied from 0 to 32 g/L h at different feed rates and concentrations. A separation efficiency of as high as 98% was obtained from the system.

30 citations

Journal ArticleDOI
TL;DR: The micropuncture evidence relating to the location and the mechanism for concentration and dilution of the urine is reviewed and it is demonstrated that in the presence of antidiuretic hormone, the tubular urine is first concentrated in the descending limb of the loop of Henle and then diluted in the ascending limb ofthe loop.
Abstract: The micropuncture evidence relating to the location and the mechanism for concentration and dilution of the urine is reviewed. As required by the countercurrent hypothesis for urine concentration, these data demonstrate that in the presence of antidiuretic hormone, the tubular urine is first concentrated in the descending limb of the loop of Henle and then diluted in the ascending limb of the loop before its final concentration in the collecting ducts. The loop of Henle is believed to function as a countercurrent multiplier system, and the vasa recta as countercurrent diffusion exchangers. Additional data are required during water diuresis before the course of events in this condition is established.

30 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of various parameters on the maximum heat flux of a vertical closed-loop pulsating heat pipe (CLPHP) and the inside phenomena that cause maximum heat flow to occur were investigated.
Abstract: The objective of this study is to experimentally investigate the effect of various parameters on the maximum heat flux of a vertical closed-loop pulsating heat pipe (CLPHP) and the inside phenomena that cause maximum heat flux to occur. A correlation to predict the maximum heat flux using the obtained results was also established. Quantitative and qualitative experiments were conducted and analyzed. A copper CLPHP and a transparent high-temperature glass capillary tube CLPHP were used in the quantitative and qualitative experiments. From the study, it was found that when the internal diameter and number of meandering turns increased, the maximum heat flux increased. However, when the evaporator section length increased, the maximum heat flux decreased. The maximum heat flux of a CLPHP occurs due to the dry-out of liquid film at the evaporator section. This occurs after a two-phase working fluid circulation changes flow pattern from countercurrent slug flow to co-current annular flow, because the vapor vel...

30 citations

Proceedings ArticleDOI
01 Jan 2002
TL;DR: In this paper, analytical solutions for the initial stage of 1D countercurrent flow of water and oil in porous media are presented for rod-like, cylindrical and spherical cores, for which water is the wetting liquid.
Abstract: Analytical solutions for the initial stage of 1D countercurrent flow of water and oil in porous media are presented. Expressions are obtained for the time dependence of the water saturation profile and the oil recovered during spontaneous countercurrent imbibition in rod-like, cylindrical, and spherical cores, for which water is the wetting liquid. Some of the analytical solutions are found to be in good agreement with existing numerical solutions and available experimental data for oil recovery from cores with strong water wettability.

30 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202358
2022115
202127
202041
201947
201849