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Showing papers on "Countercurrent exchange published in 2003"


Journal ArticleDOI
TL;DR: In this paper, the absorption−oxidation of nitrogen oxides (NOx) induced by aqueous solutions of potassium hydrogen peroxymonosulfate or oxone has been studied in a bubble column reactor operated in semicontinuous and continuous countercurrent flow modes.
Abstract: The absorption−oxidation of nitrogen oxides (NOx) induced by aqueous solutions of potassium hydrogen peroxymonosulfate or oxone (2KHSO5·KHSO4·K2SO4) in the absence and presence of SO2 has been studied in a bubble column reactor operated in semicontinuous and continuous countercurrent flow modes The influence of different process variables, such as temperature (22−55 °C), gas stream flow rate (or residence time), concentration of oxone, solution pH, feed concentrations of NO and SO2, and the presence of O2 and CO2 in the feed stream on the absorption−oxidation of NO were evaluated in the semibatch flow mode The individual and simultaneous chemistry of NOx and SO2 removal by peroxomonosulfate (KHSO5) is discussed The effects of simultaneous mass transfer and chemical reactions in the liquid phase were also investigated with a bubble column reactor operated in the continuous countercurrent flow mode using the theory of absorption accompanied by fast pseudo-mth-order reaction The rate of reaction of NO wi

93 citations


Journal ArticleDOI
TL;DR: In this article, a CFD model of the two-phase countercurrent flow in the geometry of the plate-type structured packing Mellapak 250Y was built, tested and verified.
Abstract: A CFD model of the two-phase countercurrent flow in the geometry of the plate-type structured packing Mellapak 250Y was built, tested and verified The model was applied to determine the effect of liquid and gas flow rates and physicochemical properties of the flowing liquids on the interfacial area formed on structured packing The CFD model allowed us to determine the minimum liquid flow rate at which an unbroken liquid film was observed on the packing surface The simulations confirmed that with an increase of the wetting rate the surface of the packing covered with a liquid film increased until the surface was totally covered up, while further slight changes of an interfacial area were the result of wave formation The effect of gas load (F factor) on the film surface was in the range of a calculation error Results of the CFD simulation allow us to predict the stages of film formation during liquid flow, to follow local velocity oscillations, film thickness and velocity profiles of phases

82 citations



Journal ArticleDOI
TL;DR: The vasa acts as a countercurrent multiplier and generates the hypertonic fluid in the renal medulla and the loop of henle has been the focus of extensive investigation for the last 50 years.
Abstract: the loop of henle has been the focus of extensive investigation for the last 50 years since Hargitay and Kuhn ([1][1]) first proposed that it acts as a countercurrent multiplier and generates the hypertonic fluid in the renal medulla. Until recently, however, the equally important role of the vasa

46 citations


Journal ArticleDOI
TL;DR: In this article, maps of the multi-holdup regions in co-current and countercurrent flows are presented in terms of the controlling non-dimensional parameters, which clearly demonstrate the symmetrical relationship between upward and downward cocurrent inclined flows.

43 citations


Journal ArticleDOI
TL;DR: In this article, the effects of inclination on the characteristics of laminar countercurrent liquid-liquid flow are investigated both experimentally and theoretically, and the application of two-fluid and two-plate models is explored.

43 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the performance of cocurrent and countercurrent fluidized bed membrane reactors for steam reforming of methane and found that for short bed lengths at relatively low temperatures, the cocurrent configuration is superior to countercurrent configuration.
Abstract: The theme of this work is to investigate the performance of cocurrent and countercurrent fluidized bed membrane reactors for steam reforming of methane. A mathematical model is used to simulate the experimental data and to explore the potential application of high flux membranes to enhance the methane conversion in fluidized bed membrane reactors. It has been shown that complete conversion of methane is achieved by implementing high flux membranes. The influence of some key parameters on the reactors performance has been reported. It was found that in most cases of large bed lengths, the countercurrent configuration is superior to cocurrent configuration and more sensitive to the parameters changes. However, for short bed lengths at relatively low temperatures the cocurrent configuration is superior to countercurrent configuration.

41 citations


Journal ArticleDOI
TL;DR: In this paper, both the numerical and experimental analyses in the absorption process of a bubble mode absorber were performed, where gas was injected into the bottom of the absorber at a constant solution flow rate.
Abstract: An absorber is a major component in the absorption refrigeration systems, and its performance greatly affects the overall system performance. In this study, both the numerical and experimental analyses in the absorption process of a bubble mode absorber were performed. Gas was injected into the bottom of the absorber at a constant solution flow rate. The region of gas absorption was estimated by both numerical and experimental analyses. A higher gas flow rate increases the region of gas absorption. As the temperature and concentration of the input solution decrease, the region of gas absorption decreases. In addition, the absorption performance of the countercurrent flow was superior to that of cocurrent. Mathematical modeling equations were derived from the material balance for the gas and liquid phases based on neglecting the heat and mass transfer of water from liquid to gas phase. A comparison of the model simulation and experimental results shows similar values. This means that this numerical model can be applied for design of a bubble mode absorber.

35 citations


Journal ArticleDOI
TL;DR: In this article, closed form expressions for the effectiveness-NTU relations are derived for triple concentric-tube heat exchangers including both counter-flow and parallel-flow arrangements, and some representative data for both types of flow arrangements are presented in graphical form.

34 citations


Journal Article
TL;DR: In this paper, the authors studied countercurrent gas-liquid flow in narrow rectangular channels simulated by plain and perforated fins and observed different flow patterns dependent on flow rates in the channels.

27 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical solution of differential mass-balance equations for the corresponding true countercurrent process (TCC), using as a model system the reaction A⇌B+C with each species exhibiting linear adsorption behavior, was developed.
Abstract: Simulated Moving Bed reactors (SMBR) combine chemical reaction and adsorptive separation within one single continuous and countercurrent unit. This integration promises substantial improvements in process performance, especially when applied to equilibrium-limited reactions involving such heat-sensitive products as fine chemicals and pharmaceuticals. In this work, the interplay among the relevant process design parameters (dimensionless ratios of the fluid and solid flow rates, and the Damkohler numbers for each section of the unit) is investigated. For this, an analytical solution of differential mass-balance equations for the corresponding true countercurrent process (TCC), using as a model system the reaction A⇌B+C with each species exhibiting linear adsorption behavior, was developed. Based on this solution, criteria were derived for the optimum process design with respect to productivity and solvent consumption. Comparing these results with numerical simulations of an SMBR unit shows that the TCC model does not apply to SMBR units with a finite number of columns per section, that is, units of practical relevance, because the two units exhibit different residence time distributions and, hence, lead to different degrees of conversion.

Journal ArticleDOI
TL;DR: The chromatographic performance of 1.5 cm I.D. convoluted teflon tubing was studied at low rotary speeds ranging from 34 to 105 rpm in this article.
Abstract: The chromatographic performance of 1.5 cm I.D. convoluted teflon tubing was studied at low rotary speeds ranging from 34 to 105 rpm. Results were as follows: (i) many solvent systems showed excellent retention of the stationary phase even at a high flow rate of the mobile phase; (ii) a good mixing of the two phases gave efficient solute partitioning resulting in high peak resolution; (iii) increasing the sample size caused only minor peak broadening; and (iv) increase in peak width and resolution using longer columns is predictable. Our data show that it is feasible to scale up a slow rotary countercurrent chromatograph with 1.5 cm I.D. convoluted tubing for industrial use.

Journal ArticleDOI
TL;DR: When cellular materials are immersed in a solution of high concentration, the mass transfer is considered a multi-component transport process in which simultaneous and countercurrent flows occur in this article, where the authors consider the case of a single cell.
Abstract: When cellular materials are immersed in a solution of high concentration, the mass transfer is considered a multi-component transport process in which simultaneous and countercurrent flows occur in...

Journal ArticleDOI
TL;DR: The dynamic behavior of ozonation with pollutants in a countercurrent bubble column is studied for the model establishment and the dynamic axial dispersion model proposed is employed to predict the variation of the ozone, pollutant, and oxygen concentrations profiles.

Journal ArticleDOI
TL;DR: In this article, a self-consistent system of macroscopic equations, including Leverett's equation for capillary pressure, is presented for determining experimentally relative permeability and capillary pressures as a function of saturation.
Abstract: When determining experimentally relative permeability and capillary pressure as a function of saturation, a self-consistent system of macroscopic equations, that includes Leverett's equation for capillary pressure, is required. In this technical note, such a system of equations, together with the conditions under which the equations apply, is formulated. With the aid of this system of equations, it is shown that, at the inlet boundary of a vertically oriented porous medium, static conditions pertain, and that potentials, because of the definition of potential, are equal in magnitude to pressures. Consequently, Leverett's equation is valid at the inlet boundary of the porous medium, provided cocurrent flow, or gravity-driven, countercurrent flow is taking place, and provided the porous medium is homogeneous. Moreover, it is demonstrated that Leverett's equation is valid for flow along the length of a vertically oriented porous medium, provided cocurrent flow, or gravity-driven, countercurrent flow is taking place, and provided the porous medium is homogeneous and there are no hydrodynamic effects. However, Leverett's equation is invalid for horizontal, steady-state, forced, countercurrent flow. When such flow is taking place, it is the sum of the pressures, and not the difference in pressures, which is related to capillary pressure.

Patent
20 Jun 2003
TL;DR: In this paper, a countercurrent membrane exchanger (CCME) is provided for equilibrating a carrier fluid with the sample of blood or other liquid, the output of which is coupled to a tubular direct insertion membrane probe (t-DIMP) type of membrane inlet mass spectrometer.
Abstract: A method and apparatus for the analysis of blood or other liquids by mass spectrometry to determine the partial pressures of gases and other volatile substances dissolved in the blood or other liquid in a manner independent of the solubility of the gases in the blood or other liquid. A countercurrent membrane exchanger (CCME) is provided for equilibrating a carrier fluid with the sample of blood or other liquid, the output of which is coupled to a tubular direct insertion membrane probe (t-DIMP) type of membrane inlet mass spectrometer. The CCME preferably has complementary spiral grooves on opposing metal plates for the water carrier and sample liquids so as to induce secondary flows which greatly reduce the resistance to equilibration between the liquid sample and water carrier phases. The t-DIMP is characterized by the use of Teflon™ sleeves specifically to reduce noise introduced at the connection between the silicone membrane in the t-DIMP and the steel tubing for the water carrier, by the use of radiation shields to prevent heating of the silicone membrane and water carrier to allow lower carrier flow rates, and by the heating of the section between the ion source and the vacuum pumps specifically to improve linearity of the t-DIMP.

Journal Article
TL;DR: This work brings to the fore characterizations and dynamical properties of countercurrent liquid-liquid double-pipe heat exchangers, which are compartmental and cooperative irreducible, and each of these characterizations define particular dynamical Properties of the system solutions.
Abstract: Countercurrent liquid-liquid double-pipe heat exchangers prove to be a special type of positive systems: namely, they are compartmental and cooperative irreducible. Each of these characterizations define particular dynamical properties of the system solutions. This work brings to the fore such characterizations and dynamical properties.

Journal ArticleDOI
TL;DR: In this article, the effectiveness of counter and parallel-flow heat exchanger with high velocities was investigated and the NNTU equations were derived for the case of an exponentially distributed kinetic energy.
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.

Patent
08 Aug 2003
TL;DR: In this article, the authors apply a cross flow-type multilayer countercurrent method by properly arranging plate fins inside of a layered body, where the plates are arranged in the direction orthogonal to the high-temperature fluid layer through heat transfer partition.
Abstract: PROBLEM TO BE SOLVED: To apply a cross flow-type multilayer countercurrent method by properly arranging plate fins inside of a layered body SOLUTION: High-temperature fluid plate fins 2 inclined at 45° and clearances 6 are arranged as a high-temperature fluid layer 1, low-temperature fluid plate fins 5 inclined at 45° and clearances 6 are arranged as a low-temperature fluid layer 4, and stacked in the direction orthogonal to the high-temperature fluid layer 1 through heat transfer partition, plates 3 Futher the high-temperature fluid plate fins 2 and the clearances 6 may be diagonally arranged as the high- temperature fluid layer 1, and the low-temperature fluid plate fins 5 and the clearance 6 may be diagonally arranged as the low-temperature fluid layer 4 and stacked through the heat transfer partition plates 3 When the high- temperature air to the high-temperature fluid layer 1, and the low-temperature air to the low-temperature fluid layer 4 are simultaneously sent, the temperatures of the high-temperature air and the low-temperature air are completely reversed by the countercurrent of the fluids inside of the high- temperature fluid plate fins 2 and the low-temperature fluid plate fins COPYRIGHT: (C)2003,JPO

Journal ArticleDOI
TL;DR: In this article, a mechanistic model and a simplified model are developed for describing the oil-water countercurrent flow in deviated and multilateral wells. But the model is not suitable for the case of water circulation.
Abstract: Water circulation and oil–water countercurrent flow in a deviated or multilateral well has been investigated in the present paper. Flow patterns for the countercurrent flow have been identified. Two practical criteria for determining the occurrence of countercurrent flow in deviated wells are introduced. Five categories of flow patterns for the countercurrent flow in pipes or wells are identified. Transitions among different flow patterns are proposed. Both a mechanistic model and a simplified model are developed for describing the oil–water countercurrent flow in deviated and multilateral wells. Solution procedure for using the newly-developed models is discussed.

Journal ArticleDOI
TL;DR: In this paper, two practical criteria based on the transport mechanisms of a liquid layer and a liquid droplet have been developed for determining the occurrence of oil-water countercurrent flow in deviated or multilateral wells.
Abstract: Water circulation and oil–water countercurrent flow in a deviated well has been investigated in the present article. Flow patterns for the countercurrent flow have been identified. Two practical criteria based on the transport mechanisms of a liquid layer and a liquid droplet have been developed for determining the occurrence of oil–water countercurrent flow in deviated or multilateral wells. The criteria can also be applied to determine the liquid loading-up conditions of gas wells. Well deviation, well size, and oil density are the three major factors that affect the occurrence of oil–water countercurrent flow. The smaller the wellbore size, the larger the well deviation, or the denser the oil phase, the lower the minimum oil flow rate is required to avoid the occurrence of oil–water countercurrent flow or water circulation. Excellent agreement has been achieved between the model prediction and the field and laboratory observations. A modified equation has also been proposed for determining the...

Journal ArticleDOI
TL;DR: In this paper, a new technique for the continuous and selective heating of the solid phase in a flowing dispersion was proposed, implemented in a heater-valve-pulsed apparatus unit.
Abstract: A new technique is suggested for the continuous and selective heating of the solid phase in a flowing dispersion. This technique is implemented in a heater–valve-pulsed apparatus unit. Mathematical models are developed for the cocurrent and countercurrent designs of the heater. Analytical solutions are obtained for the model equations, and parameters governing the continuous selective heating of the solid phase are determined. A design algorithm is suggested for the unit.

Journal ArticleDOI
TL;DR: In this article, the gravity separation of particles from the laminar flow of a liquid in a flat channel is studied, taking into account the particle size distribution, the flow velocity field, and also the conditions for equilibrium of single particles and their structural formations (a layer of particles or noncoalescing drops) on the channel walls.
Abstract: The mechanism of gravity separation of particles from the laminar flow of a liquid in a flat channel is studied. This mechanism takes into consideration the particle size distribution, the flow velocity field, and also the conditions for equilibrium of single particles and their structural formations (a layer of particles or noncoalescing drops) on the channel walls.

Patent
24 Jun 2003
TL;DR: In this paper, a process and apparatus for low-temperature fractionation of air in a distillation column system for nitrogen-oxygen separation is described. But the authors do not consider the effects of mixing a mixture of krypton and xenon.
Abstract: A process and apparatus for low-temperature fractionation of air in a distillation column system for nitrogen-oxygen separation (5, 6) introduces into first feed air stream (4) into a distillation column system for nitrogen-oxygen separation. An oxygen-rich fraction (22) from the distillation column system for nitrogen-oxygen separation is pressurized (23) in liquid form and is added (25) to a mixing column (26). A heat transfer medium stream is introduced into the lower region of the mixing column (26) and is brought into countercurrent contact with the oxygen-rich fraction (22, 25). Gaseous top product (260) from the upper region of the mixing column (26) is introduced into an additional column (27). A liquid (38, 39, 40, 41) from the lower or middle region of the mixing column is introduced into the distillation column system. A krypton- and xenon-containing oxygen stream (44, 46, 47, 48) from the distillation column system is introduced into a krypton-xenon enriching column (36) from which a krypton- and xenon-enriched fraction (51) is obtained. A krypton- and xenon-depleted top fraction (28) is obtained from the upper region of the additional column (27).

Journal ArticleDOI
TL;DR: In this article, a falling liquid film interacts, through the free interface, with the gas phase, and the result of these vortices is an increase of transfers compared to the smooth wall.


Patent
05 Feb 2003
TL;DR: In this paper, a vertically mounted reduced pressure evaporation falling-film heat exchange equipment, its falling film heat exchange tube is downward connected with falling film liquor circulating container, and its upper portion is equipped with reduced pressure evaporating and temp-reducing flow-guide system which is communicated with atmosphere and can be used for making negative pressure countercurrent eva-tion, temp reducing and heat exchange.
Abstract: The present invention relates to a heat exchange equiopment, in particular, it is a vertically-mounted reduced pressure evaporation falling-film heat exchange equipment, its falling-film heat exchange tube is downward connected with falling-film liquor circulating container, and its upper portion is equipped with reduced pressure evaporating and temp.-reducing flow-guide system which is communicated with atmosphere and can be used for making negative pressure countercurrent evaporation, temp.-reducing and heat exchange, and its periphery is equipped with closed circulating cooling system to supply heat.

Patent
19 Feb 2003
TL;DR: In this article, a process for cleaning water includes mixing the flocculant with the water to be treated in water inlet pump, and reaction between air bubbles and floc in countercurrent copolymerizing reactor, flowing the water downward and the air upward, discharging the resultant water from bottom of reactor and discharging dregs from top of reactor.
Abstract: A process for cleaning water includes mixing the flocculant with the water to be treated in water inlet pump, flocculating and reaction between air bubbles and floc in countercurrent copolymerizing reactor, flowing the water downward and the air upward, discharging the resultant water from bottom of reactor, and discharging dregs from top of reactor.

Patent
11 Apr 2003
TL;DR: In this article, a process for upgrading a liquid petroleum or chemical stream wherein said feedstream flows countercurrent to the flow of a treat gas, such as a hydrogen-containing gas, in at least one reaction zone is described.
Abstract: A process for upgrading a liquid petroleum or chemical stream wherein said feedstream flows countercurrent to the flow of a treat gas, such as a hydrogen-containing gas, in at least one reaction zone. The feedstream treated so that it is substantially free of particulate matter and foulant precursors.

Patent
Arends Gesine1, Peter Riegger1
28 Mar 2003
TL;DR: In this article, the authors describe a system in which the heating flow passes entirely countercurrent to the hydrocarbons through both the first and second reformers (2, 3) during start-up, and the heating unit is central with respect to the reformers and heaters.
Abstract: In one phase of operation, the heating flow (6) passes through the second reformer (3) countercurrent to the hydrocarbon-containing flow (4). In one phase of operation, the heating flow passes entirely countercurrent to the hydrocarbons (4) through both the first and second reformers (2, 3). The heating flow (6) is passed through a second heater (9), to heat both reformers (2, 3) during start-up. In a variant, the heater is located between the reformers. Inlet and/or outlet (12, 11) of the first and/or second heater include controlled dosing equipment for the heating flow (6). The reformers and heaters are coaxial. The heating unit (5) is central with respect to the reformers and heaters (8, 9). The corresponding installation and vehicle including it, are also claimed.