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Showing papers on "Countercurrent exchange published in 1983"


Journal ArticleDOI
TL;DR: In this paper, a calculation method for predicting the gas separation performance of a permeator with asymmetric membrane is presented, which takes into account the permeate pressure drop and is applicable to both hollow-fiber and spiral-wound modules.
Abstract: The permeation behavior of the high-flux asymmetric membrane differs from that of the conventional symmetric membrane. A calculation method for predicting the gas separation performance of a permeator with asymmetric membrane is presented. The model takes into account the permeate pressure drop and is applicable to both hollow-fiber and spiral-wound modules. The effect of permeate-feed flow pattern on module performance is analyzed. It is shown that for the high-flux asymmetric membrane, the countercurrent flow pattern is not necessarily always the preferred operating mode. The mathematical model is verified by large-scale field pilot-plant experiments for helium recovery from natural gas using large hollow-fiber modules (220 m2/unit).

129 citations


Journal ArticleDOI
TL;DR: In this paper, an envelope theory for onset of flooding in inclined stratified flow is developed, which agrees better than the experimental data than other theories. And some basic flow parameters, such as mean film thickness and interfacial friction factor in the roll-wave regime (near-flooding) have been measured.
Abstract: Flooding of stratified countercurrent steam-water flow in nearly-horizontal and in inclined flat-plate geometries is investigated. An envelope theory for onset of flooding in inclined stratified flow is developed, which agrees better than the experimental data than other theories. In addition, some basic flow parameters, such as mean film thickness and interfacial friction factor in the roll-wave regime (near-flooding) have been measured. Empirical correlations for these parameters were sought, which are essential in the flooding analysis.

88 citations


Journal ArticleDOI
TL;DR: The temperature decrease of the arterial blood passing the rete is rather constant over a wide range in body weight, but larger than previously reported body-to-brain temperature differences.
Abstract: A morphometric analysis has been made of the rete ophthalmicum which is a functional arteriovenous heat exchange system in the heads of birds. The morphological data were obtained from histological sections of the rete from 40 species of birds covering a weight range of 20,000-fold. The maximal number of retial arteries, the length, the diameter of the arteries, the total arterial cross-sectional area, and the maximal exchange area have been expressed in terms of allometric equations. Other parameters important for the countercurrent heat exchange effect have been estimated or calculated. By use of simple physical laws for ideal heat exchangers, it is shown that the temperature decrease of the arterial blood passing the rete is rather constant over a wide range in body weight, but larger than previously reported body-to-brain temperature differences. The results are consistent with the heat exchange function of the rete and provide support for the idea that the rete, besides serving as a cooling system for the brain, also may be important in reducing heat loss from the eye.

66 citations


Journal ArticleDOI
TL;DR: In this article, an analysis of the flow field of a rotating compressible fluid in a cylinder with internal sources or sinks of mass, momentum, or energy is presented using an expansion in eigenfunctions of the corresponding homogeneous equation.
Abstract: An analysis is presented that describes a model of the flow field of a rotating compressible fluid in a cylinder with internal sources or sinks of mass, momentum or energy, A solution of the mathematical model is obtained using an expansion in eigenfunctions of the corresponding homogeneous equation. The internal sources or sinks produce countercurrent flows analogous to flows generated by boundary conditions in the classical analysis of the problem. The application of this model to the flow driven by a feed stream or a scoop is discussed. Some sample calculations are presented that illustrate the countercurrent flow produced by sources of mass, the three components of momentum, energy and a mass source/sink combination. Calculations simulating feed introduction and a tails-removal scoop have been performed and the fluid-dynamics solutions have been used to calculate the optimum separative performance of the example centrifuge.

47 citations


Journal ArticleDOI
TL;DR: In this article, the authors compared the performance of countercurrent and cocurrent flotation circuits and found that countercurrent circuits were superior to cocurrent circuits in all respects, including feedback loops and sump delays.

40 citations


Journal ArticleDOI
TL;DR: A differential equation model of the renal countercurrent system has been developed and physiological data from nephron segments were incorporated together with recently suggested urea recycling from renal pelvis to inner medulla and, particularly, an exponential reduction in the number of collecting tubules towards the renal papilla.
Abstract: A differential equation model of the renal countercurrent system has been developed and physiological data from nephron segments were incorporated together with recently suggested urea recycling from renal pelvis to inner medulla and, particularly, an exponential reduction in the number of collecting tubules towards the renal papilla. The role of these features for the countercurrent concentrating mechanism has been studied by simulation runs. The computations, using the multiple shooting method, provide predictions about concentration profiles for salt and urea in tubes (nephron segments) and in the central core along the entire medullary countercurrent system. The results indicate that this model, without active salt or urea transport in the inner medulla, yields concentration gradients along the medullary axis compatible with those measured in the tissue.

37 citations


Journal ArticleDOI
TL;DR: In this article, the location of the top of the atmosphere boundary of a cylindrical rotor of a high-speed countercurrent gas centrifuge with UF/sub 6/ for the enrichment of uranium was investigated.
Abstract: A vacuum exists in the central region of the cylindrical rotor of a high-speed countercurrent gas centrifuge when operated with UF/sub 6/ for the enrichment of uranium. Since solutions of the Navier-Stokes equation are used to determine the isotopic distribution in the rotor, the location of the vacuum core boundary has a direct effect on the predicted separative work of the gas centrifuge. Because criteria for terminating the continuum region based on the Knudsen number are somewhat arbitrary, an approximate model developed by Onsager, which yields an analytical solution, has been used to evaluate the location of the boundary of the vacuum core more correctly. The results show that the location of this ''top of the atmosphere,'' in density scale heights, changes with the peripheral speed of the centrifuge. Using this location in the calculation of separation performance parameters of the gas centrifuge reduces, at the higher peripheral speeds, the contribution of axial diffusion to the effective stage length of a theoretical stage in the centrifuge. The correction due to imposing the top of the atmosphere limitation on axial diffusion becomes significant at high speeds and low countercurrent circulation rates.

35 citations


Patent
20 Jan 1983
TL;DR: A liquid-liquid contacting apparatus is described in this paper, which is useful in extracting mercaptans from a hydrocarbon stream such as cracked gasoline by nonturbulent countercurrent contacting of the hydrocar stream with an aqueous caustic solution.
Abstract: A liquid-liquid contacting apparatus is disclosed. The apparatus is useful in extracting mercaptans from a hydrocarbon stream such as cracked gasoline by nonturbulent countercurrent contacting of the hydrocarbon stream with an aqueous caustic solution. The denser liquid phase flows downward from an upper phase separation zone through a connecting cylindrical contacting zone into a lower phase separation zone. Liquid withdrawal and addition means communicate with each separation zone. A mass of fibrous contacting strands is suspended in the contacting zone. The contacting strands are preferentially wetted by either of the two liquid phases to provide a large surface area which enhances extraction capacity.

33 citations


Journal ArticleDOI
TL;DR: In this paper, a criterion for flooding in the countercurrent flow of two fluids in horizontal tubes and channels is developed, which exhibits a dependence upon the density ratio of the fluids beyond that present in the criterion of Wallis (1969).

25 citations


Patent
30 Sep 1983
TL;DR: In this article, the authors combine a simulated countercurrent flow system with a stationary magnetically stabilized fluidized bed to achieve continuous adsorption-desorption to separate components of a feedstream.
Abstract: The sorption process involves combining a simulated countercurrent flow system with a stationary magnetically stabilized fluidized bed to achieve continuous adsorption-desorption to separate components of a feedstream.

22 citations


Journal ArticleDOI
TL;DR: In this paper, the dependence of the separation efficiency on the outflow of the enriched solution and on the convection through the membrane has been verified, and the experimental results confirm the relationship between separation efficiency and the difference in ionic equivalent conductance.
Abstract: Countercurrent electrolysis in a porous membrane has been used to separate cations in systems LiCl-NaCl-H2O, LiCl-CaCl2-H2O, LiCl-BaCl2-H2O, LiCl-KCl-H2O, and LiCl-NaCl-KCl-H2O. The experimental results confirm the relationship between the separation efficiency and the difference in ionic equivalent conductance. Furthermore, the dependence of the separation efficiency on the outflow of the enriched solution and on the convection through the membrane has been verified.

Journal ArticleDOI
TL;DR: In this article, the authors developed numerical algorithms for the simultaneous solution of the mass transfer and hydrodynamic equations for swarms of liquid drops in a countercurrent flow liquid extraction column.

Patent
16 May 1983
TL;DR: A process and apparatus for production of liquid and gaseous fuels from solid organic carbonaceous materials by reacting free falling solids in a countercurrent gas stream is described in this article.
Abstract: A process and apparatus for production of liquid and gaseous fuels from solid organic carbonaceous materials by reacting free falling solids in a countercurrent gas stream The process is conducted with a lean solids phase which provides good process control and uniform flow of solids even in the presence of condensation and refluxing of liquids on the solid particles Rapid heatup rates provide high carbon conversions Oil shales of the eocene period are particularly well suited for the process of this invention A reactor particularly suited for conducting reactions between free falling solids and countercurrent flowing gas streams is disclosed together with preferred methods for introduction of solid feeds to the top of the reactor

Journal ArticleDOI
TL;DR: In this paper, the influence of the aerator, the aeration rate and the loop and the recirculation rate of liquid through the loop on the performance of tower reactors is investigated.
Abstract: Equipment effects in culturing single-cell organisms in tower reactors. The influence of the aerator, the aeration rate and the loop and the recirculation rate of liquid through the loop on the performance of tower reactors are investigated. Also the effect of different internals, upward and/or downward as well as countercurrent flow of gas and liquid and the influence of the medium are considered. The performance of equipment can be varied over a wide range by means of these construction and operational parameters. This allows adaptation of these reactors to a particular production process. Difficulties arise when the reactor volume attains very high values. In such cases, fast and uniform distribution of energy, substrate, and oxygen added to the system and the removal of the heat, gas bubbles, and CO2 from the medium cause considerable difficulties. Further investigations will be necessary to develop quantitative relationships for scale-up purposes.

01 Mar 1983
TL;DR: In this article, a finite difference method is presented for the numerical simulation of the axisymmetric countercurrent flows in gas centrifuge and a time-marching technique is used to relax an arbitrary initial condition to the desired steady-state solution.
Abstract: A finite difference method is presented for the numerical simulation of the axisymmetric countercurrent flows in gas centrifuge. A time-marching technique is used to relax an arbitrary initial condition to the desired steady-state solution. All boundary layers may be resolved, and nonlinear effects may be included. Numerical examples are presented. It is concluded that this technique is capable of accurately predicting the performance of a wide variety of machines under all operating conditions of interest.

Journal ArticleDOI
TL;DR: In this paper, it is verified that the existing formulation for the calculation of the elementary separation factor holds independent of whether there is such an anomaly in the isotope distribution for the less mobile cation.
Abstract: Abstract In countercurrent electromigration of molten binary mixtures with a common anion in which each cation is composed of two isotopes, the less mobile cation is enriched toward the anode, and, at the same time, the isotopes of this cation become distributed in a complicated way. Thus, the zone next to the anode where the heavy isotope is enriched is immediately followed by a region where a slight enrichment of the light isotope occurs, while for the more mobile cation the heavy isotope is enriched in both these regions. This phenomenon has been observed in experiments with the systems (Li-K)NO3 and (Li-K)Cl and it has also been reproduced by analyzing the flow equations for the constituent components numerically with a computer. It is verified that the existing formulation for the calculation of the elementary separation factor holds independent of whether there is such an anomaly in the isotope distribution for the less mobile cation.

Journal ArticleDOI
TL;DR: Analyse, a l'aide d'un modele de simulation sur ordinateur, des performances of un echangeur de chaleur a ecoulement a contrecourant a contact direct direct entre l'air and des goutelettes d'eau de dimensions uniformes as mentioned in this paper.
Abstract: Analyse, a l'aide d'un modele de simulation sur ordinateur, des performances d'un echangeur de chaleur a ecoulement a contrecourant a contact direct direct entre l'air et des goutelettes d'eau de dimensions uniformes

Patent
01 Jul 1983
TL;DR: In this article, the authors describe a cyclone-like device for the exchange of heat or material between a fluid and a finely-divided material in suspension in this fluid, which is intended for industrial processes of heat treatment (heating, calcining, cooling).
Abstract: The invention relates to a device making it possible to carry out a methodical exchange of heat or of matter between a fluid and a finely-divided material in suspension in this fluid. It consists of an axisymmetric fluid casing 2 at a maximum distance from the axis; at one end of the axis, an annular material inlet 5 and a circular fluid outlet 3 which are coaxial, the first being outside the second; at the other end of the axis, a material outlet. Suitable operating characteristics enable a radial countercurrent circulation of the fluid (centripetal movement) and of the material (centrifugal movement) to be obtained in the exchanger. The separation of the fluid and of the material after exchange may be improved by a disc 7 for separating overflow from underflow. The pressure drop of the fluid in the cyclone may be reduced by a turbine driven by the fluid at its exit from the exchanger 8. The temperature profile in the exchanger may be controlled by the supply or abstraction of heat and/or of material inside the exchanger 9. The device according to the invention is particularly intended for the industrial processes of heat treatment (heating, calcining, cooling) and of dissolving or crystallising.

Patent
07 Apr 1983
TL;DR: In this paper, the authors proposed a method for processing a material into a granular product, which involves atomising the suspension, feeding a heat transfer medium (4) in a helical stream into a zone which is situated below the atomising zone, drying the suspension with the aid of the heat transferred medium in cocurrent and in countercurrent motion downwards up to a temperature at which the required product properties are achieved, and ducting off the heat-treated material from the heat treatment zone.
Abstract: The invention involves the technology of processing a material into a granular product. The invention involves atomising the suspension (1), feeding a heat transfer medium (4) in a helical stream into a zone which is situated below the atomising zone, drying the suspension (1) with the aid of the heat transfer medium (4) in cocurrent and in countercurrent thereto while at the same time separating the fine fractions (5) of the dried material by the cocurrent stream of the heat transfer medium (4), ducting off the spent heat transfer medium (4), the heat treatment of the grains formed during drying in countercurrent to the specified heat transfer medium (4) during their helical motion downwards up to a temperature at which the required product properties are achieved, and ducting off the heat-treated material from the heat treatment zone. The device for implementing this process comprises a chamber (3) which is designed so as to have a cross-section which varies with height, means (2) for atomising the suspension (1), which are arranged in the upper part of chamber's (3) which has the largest dimensions, means (13,27) for feeding in the heat transfer medium (4), which are arranged helically in the lower part of the chamber (3), the pitch and the diameter of the helix turns being designed to a variable with the chamber height and increasing in size in the direction towards the means (2) for atomising the suspension (11). The invention can be used in the heat treatment of mineral suspensions, for example of chalk and cement raw material muds or ore concentrates and for processing wastes in various branches of production.

Journal ArticleDOI
TL;DR: Analysis of the countercurrent process provides some insights into the importance of tracer exchange between capillaries in vascular beds not arranged in orderly countercurrent networks.
Abstract: A model for passive countercurrent capillary exchange is presented, and solutions for transient responses are obtained. The model is applied to an analysis of hydrogen gas exchange in the renal medulla. Estimates of medullary flow per gram tissue are in reasonable agreement with estimates obtained with vascular tracers and similar to the values for whole kidney. Semilog plots of tissue washout curves appear nearly linear but will overestimate flow if the countercurrent process is inefficient and will underestimate flow if the countercurrent exchange is efficient. Analysis of the countercurrent process also provides some insights into the importance of tracer exchange between capillaries in vascular beds not arranged in orderly countercurrent networks. Capillaries in other vascular beds that are close enough together to permit considerable exchange of inert gas tracers may simulate countercurrent effects if some of the adjacent capillaries are in countercurrent or staggered cocurrent arrangements.


Patent
20 Jul 1983
TL;DR: In this paper, the deodorization and deacidification of cocoa butter and cocoa butter substitutes is performed according to the principle of continuous countercurrent falling film motive steam distillation in an externally imposed temperature field in at least two different zones, in which different flow and flow conditions prevail for the liquid film or the vapors.
Abstract: The deodorization and / or deacidification of cocoa butter and cocoa butter substitutes takes place according to the principle of continuous countercurrent falling film motive steam distillation in an externally imposed temperature field in at least two different zones, in which different flow and flow conditions prevail for the liquid film or the vapors In the initial zone 10, which immediately follows the liquid task and ensures at least two separation stages, the vapors flow through trickling channels with a hydraulic diameter of 120 to 150 mm. In the final zone 22, which ensures six to eight theoretical separation stages, the vapors flow through trickle channels with a hydraulic diameter of less than 120 mm, preferably less than 80 mm. The liquid is applied to the head of the initial zone at a temperature between 150 and 200 ° C., possibly after degassing, dewatering and degumming; the temperature of the deacidified and / or deodorized product is max. 10 ° K above the inlet temperature in the initial zone, for which purpose the inlet temperature of the heating medium conducted in countercurrent or cross / countercurrent to the flowing liquid film in no case exceeds the film removal temperature by more than 10 ° K and is kept below 205 ° C; the working pressure is below 2.0 mbar in the head of the starting zone and max. in the bottom of the closing zone. Kept 1.6 mbar above that of the initial zone; the formation of a significant liquid level is avoided in the liquid collectors of the zones working one behind the other; and the carrier steam is supplied in an amount of 2 to 10 kg of steam per 100 kg of liquid charged. If required, a flash container 46 can be connected between the high-temperature heat exchanger 9 and the falling film column 10, in which the raw cocoa butter brought to the working temperature is subjected to a flash treatment at practically the working pressure prevailing in the falling film column 10.

Patent
16 Apr 1983
TL;DR: In this article, the authors proposed a method to prevent the contact of countercurrent preventing material with a transparent plate and a heat collecting plate for keeping the efficiency of heat collection at a high level by a method in which plural spacers are fixed to proper places on the back of a transparent substrate provided in the upper opening portion of a box, and the countercurrent protecting material is fixed the lower side of the spacers.
Abstract: PURPOSE:To prevent the contact of c countercurrent preventing material with a transparent plate and a heat collecting plate for keeping the efficiency of heat collection at a high level by a method in which plural spacers are fixed to proper places on the back of a transparent plate provided in the upper opening portion of a box, and the countercurrent preventing material is fixed the lower side of the spacers. CONSTITUTION:In a solar heat collector 1, heat insulators 2 are provided to the internal side walls and bottom of a box, an aluminum foil 3 is laid above the heat insulator 2, a heat collector 6 is fixed to the upper part of the bottom aluminum foil 3, and a transparent plate 7 is provided at the upper opening portion of the box. In this case, a countercurrent preventing film 9 is provided between the transparent plate 7 and the heat collector 6, when one or plural spacers 8 of a heat-resistant and transparent synthetic resin, etc., having U- shaped cross section, are fixed with an adhesive to the back of the transparent plate 7. Then, the countercurrent preventing film 9 is fixed with screws to the lower sides of the spacers 8 fixed to the transparent plate 7.


Journal ArticleDOI
TL;DR: In this article, a steady-state analytical has been developed to predict channel pressure drop as a function of inlet vapor flow rate and applied heat flux during conditions of countercurrent two-phase flow.
Abstract: A steady-state analytical has been developed to predict channel pressure drop as a function of inlet vapor flow rate and applied heat flux during conditions of countercurrent two-phase flow. The interfacial constitutive relations utilized are flow surface dependent and allow for the existence of either smooth or way liquid films. A computer code was developed to solve the analytical model. Predictions of ..delta..p versus vapor flow rate were found to agree favorably with experimental data from adiabatic, air/water systems. In addition, the model was used to predict countercurrent flow conditions in heated channels characteristic of a BWR/4 nuclear reactor fuel assembly.

Patent
Andrija Fuderer1
08 Feb 1983
TL;DR: In this paper, a partial countercurrent pressure reduction prior to the conventional countercurrent release is used to release void volume gas from the main adsorber bed to an auxiliary bed, which can simultaneously release gas at its outlet end.
Abstract: The bed utilisation and the product yield, especially in pressure swing adsorption processes designed for high pressure applications, are improved in that the cocurrent pressure reduction is ended at a relatively high intermediate pressure level. Additional void volume gas is liberated from each main adsorber bed by partial countercurrent pressure reduction prior to the conventional countercurrent release. This additional gas is passed to an auxiliary bed, which can simultaneously release gas at its outlet end, as a result of which the auxiliary bed is depressurised by the intermediate pressure level in the cocurrent flow. The gas released in this manner is passed to the outlet end of one or more auxiliary beds and/or one or more main beds for pressure equalisation and/or flushing purposes. The auxiliary bed belongs to an adsorber bed auxiliary group, which includes fewer and smaller beds than the main bed system. The auxiliary beds are not subjected to a higher pressure than the intermediate pressure level.

Journal ArticleDOI
TL;DR: In this article, the authors present the numerical simulation of the countercurrent wave of an exothermal reaction and the dependences of its characteristics on the "input" parameters of the system.
Abstract: The article presents the numerical simulation of the countercurrent wave of an exothermal reaction: the dependences of its characteristics on the “input” parameters of the system.

Patent
26 Apr 1983
TL;DR: In this paper, a gas-fired water heater is described, consisting of a fan, a pre-mixing device, a gas burner, a heat exchanger, and an exhaust gas heat exchange.
Abstract: A gas-fired water heater is described, consisting of a fan (1), a pre-mixing device (2), a gas burner (3), a heat exchanger (4) and an exhaust gas heat exchanger (5). The gas-fired burner (3) works as an over-stoichiometric mixing burner and has a cooled burner plate (9), on the rear side, with a plurality of mixture passage openings (10). The heat exchanger (4) extends through two adjacent chambers (6,7) through which exhaust gas flows in opposite directions. The condensation heat exchanger (5) works in countercurrent and consists of star-shaped profiles through which heating water flows centrally and which are arranged vertically. The exhaust gas heat exchanger (5) and the pre-mixing device (2) run parallel to each other.