Showing papers on "Countercurrent exchange published in 2011"

Desalination with a Cascade of Cross-Flow Hollow Fiber Membrane Distillation Devices Integrated with a Heat Exchanger

Abstract: Cost-efficient desalination technology was developed successfully by integrating a countercurrent cascade of the novel cross-flow direct contact membrane distillation (DCMD) devices and solid polymeric hollow fiber-based heat exchange devices Simulations have been carried out for the whole DCMD cascade to project values of gained output ratio (GOR) as a function of the number of DCMD stages as well as other important factors in the cascade vis-a-vis the temperatures and flow rates of the incoming hot brine and cold distillate streams The simulation results were verified with experimental results from cascades consisting of two to eight stages The numerical simulator predicts a GOR of 12 when unequal flow rates of the incoming brine and distillate streams are used An artificial sea water was concentrated eight times successfully when a countercurrent cascade composed of four stages of the DCMD modules and a heat exchanger was used during the DCMD process © 2010 American Institute of Chemical Engineers AIChE J, 2011

Semianalytical solutions for cocurrent and countercurrent imbibition and dispersion of solutes in immiscible two‐phase flow

Abstract: [1] We derive a set of semianalytical solutions for the movement of solutes in immiscible two-phase flow. Our solutions are new in two ways: First, we fully account for the effects of capillary and viscous forces on the transport for arbitrary capillary-hydraulic properties. Second, we fully take hydrodynamic dispersion for the variable two-phase flow field into account. The understanding of immiscible two-phase flow and the simultaneous miscible displacement and mixing of components within a phase is important for many applications, including the location of nonaqueous phase liquids in the subsurface, the design of contaminant cleanup procedures, the sequestration of carbon dioxide, and enhanced oil-recovery techniques. For purely advective transport we combine a known exact solution for the description of immiscible two-phase flow with the method of characteristics for the advective transport equations to obtain solutions that describe cocurrent flow and countercurrent spontaneous imbibition and advective transport in one dimension. We show that for both cases the solute front can be located graphically by a modified Welge tangent. For the advective-dispersive solute transport, we derive approximate analytical solutions by the method of singular perturbation expansion. On the basis of this, we obtain analytical expressions for the growth of the dispersive zone for the case with and without the influence of capillary pressure. We show that for the case of spontaneous countercurrent imbibition the order of magnitude of the growth rate is far smaller than that for the viscous limit. We give some illustrative examples and compare the analytical expressions with numerical reference solutions.

Countercurrent tangential chromatography for large-scale protein purification.

Abstract: Recent advances in cell culture technology have created significant pressure on the downstream purification process, leading to a “downstream bottleneck” in the production of recombinant therapeutic proteins for the treatment of cancer, genetic disorders, and cardiovascular disease. Countercurrent tangential chromatography overcomes many of the limitations of conventional column chromatography by having the resin (in the form of a slurry) flow through a series of static mixers and hollow fiber membrane modules. The buffers used in the binding, washing, and elution steps flow countercurrent to the resin, enabling high-resolution separations while reducing the amount of buffer needed for protein purification. The results obtained in this study provide the first experimental demonstration of the feasibility of using countercurrent tangential chromatography for the separation of a model protein mixture containing bovine serum albumin and myoglobin using a commercially available anion exchange resin. Batch uptake/desorption experiments were used in combination with critical flux data for the hollow fiber filters to design the countercurrent tangential chromatography system. A two-stage batch separation yielded the purified target protein at >99% purity with 94% recovery. The results clearly demonstrate the potential of using countercurrent tangential chromatography for the large-scale purification of therapeutic proteins. Biotechnol. Bioeng. 2011; 108:582–591. © 2010 Wiley Periodicals, Inc.

Heat-transfer fluids and use thereof in countercurrent heat exchangers

Abstract: The invention relates to a ternary composition comprising difluoromethane, 1,3,3,3-tetrafluoropropene and a hydrocarbon-derived compound containing at least two fluorine atoms and having a boiling point of between -30 and -20°C, which is selected from 1,1-difluoroethane, 1,1,1,2-tetrafluoroethane and 2,3,3,3-tetrafluoropropene. This composition is particularly suitable for use as a heat-transfer fluid in the presence of countercurrent heat exchangers.

Multiple shell pass countercurrent-growth tube heat exchanger

Abstract: The invention discloses a multiple shell pass countercurrent-growth tube heat exchanger which is characterized by comprising a shell (5), a channel box (2) and tube plates (3) and (8), wherein the tube plates are arranged on the two ends of the shell; the channel box (2) is connected with the outer side of the tube plate (3), a dummy plate is arranged in the channel box (2), and the other side of the shell is provided with an end cover (11); a heat exchange tube (6) is arranged in the shell and penetrates through the tube plates (3) and (8) to be communicated with the channel box and the end cover; and the shell is provided with a longitudinal countercurrent-growth guide plate (7) and a lateral growth disturbance guide plate (12) The heat exchanger of the invention is provided with the longitudinal countercurrent-growth guide plate and the lateral growth disturbance guide plate in the shell to realize that fluid in the shell pass in the tube heat exchanger and fluid in the tube form countercurrent and quick flowing heat exchange along the axial direction, thus reducing the heat transfer temperature difference between the fluids and improving the heat exchange efficiency

Heat Supply and Hydrogen Yield in an Ethanol Microreformer

Abstract: A simulation study of a microreactor for steam reforming of ethanol (ESR) over a washcoated Pd catalyst is reported in the present manuscript. Both co- and countercurrent configurations are considered for the streams of reactants and flue gas through microchannels of a square section. Two contiguous channels, assumed as representative of the whole reactor behavior, are simulated using a 1D pseudohomogeneous model. The microreactor performance is analyzed for different heat-supply strategies and channel sizes. The results demonstrate that the ESR in the microreactor is strongly controlled by the heat supply. The hydrogen yield has a marked dependence on the total amount of heat transferred from the flue gas to the reformate and the axial distribution of the heat flow. The cocurrent-flow configuration proved to yield the higher performance. While smaller channels work better for cocurrent operation, an optimum compromise value is found for the channel size in countercurrent flow.

Longitudinal Solid-Liquid Countercurrent Contact Method, Method of Washing Solid Particles, Method of Manufacturing Poly(Arylene Sulfide) and Apparatus

Abstract: A longitudinal solid-liquid countercurrent contact method and apparatus are provided in which an aqueous slurry containing solid particles is supplied from an upper part and is caused to pass through a plurality of contact-processing chambers connected in a vertical direction while being caused to proceed downward, a contacting liquid is supplied from a lower part and is caused to pass through the plurality of contact-processing chambers connected in the vertical direction while being caused to proceed upward, and the aqueous slurry and the contacting liquid are caused to be continuously subjected to countercurrent contact, wherein the viscosity of a liquid phase in at least one of the contact-processing chambers is controlled, and especially the viscosity η 1 of a liquid phase in a contact-processing chamber positioned at an uppermost part is controlled to fall within a range of 0.9≦η 1 /η 0 ≦2.0 with respect to the reference viscosity η 0 as the viscosity of a predetermined reference composition of a liquid phase at a predetermined temperature.

Experimental investigation of the impact of flow velocity on grout propagation during chemical grouting into a fracture with flowing water

Abstract: Presented a series of scaled model tests to investigate the influence of water flow velocity on grout propagation and sealing-off effect of chemical grouting into a fracture with flowing waterThe results indicate that the grout penetration lengths in countercurrent direction and perpendicular direction to water flow,the stabilized volume,and the water sealing-off rate decrease with increasing water flow rateThe velocity of water flow has more influence on the penetration length in the countercurrent direction than in the perpendicular directionA theoretical model was used to calculate the penetration lengths in both upstream and downstream side with varying water flow rateThe calculations show that the velocity of water flow has a more significant influence on grout propagation in the upstream side than in other directions,iethe penetration length in the upstream side decreases more obviously with increasing water flow rateTherefore,the influence of groundwater flow velocity should be taken into consideration in grouting in order to reach satisfactory effectThe spacing between grouting boreholes should be reduced with increasing groundwater flow rate

On the theory of countercurrent flow in a rotating viscous heat-conducting gas

Abstract: The countercurrent flow in a gas centrifuge is simulated. Mechanical and thermal methods for its excitation are discussed; thermal restructuring, the thermal control of the velocity field, and a shift in the inversion point are analyzed; and the formation of overtone flows in the rarefaction zone is studied.

Vapor-liquid heat and/or mass exchange device

Abstract: The invention is directed toward a vapor-liquid heat and/or mass exchange device that can be used in an integrated heat and/or mass transfer system. To achieve high heat and mass transfer rates, optimal temperature profiles, size reduction and performance increases, appropriately sized flow passages with microscale features, and countercurrent flow configurations between working fluid solution, vapor stream, and/or the coupling fluid in one or more functional sections of the desorber are implemented. In one exemplary embodiment of the present invention, a desorber section utilizes a heating fluid flowing in a generally upward direction and a concentrated solution flowing in a generally downward direction with gravity countercurrent to the rising desorbed vapor stream. To further increase the efficiency of the system, various types of column configurations can be used. Additionally, the surfaces of the microchannels can be altered to better transfer heat.

Continuous Separation of an H2SO4/CuSO4 Mixture by Diffusion Dialysis

Abstract: The separation of a mixture of sulfuric acid and copper sulfate is experimentally investigated in a two-compartment countercurrent dialyzer at steady state using an anion-exchange membrane. The dialysis process is characterized by the recovery yield of acid, the rejection coefficient of salt, and the permeability coefficient of the membrane. The simultaneous transport of sulfuric acid and copper sulfate is quantified by four phenomenological coefficients, which are dependent on the acid and salt concentrations in the feed. They are determined by a procedure consisting of (i) the numerical integration of the basic differential equations describing the concentration profiles of both components on both sides of the membrane and (ii) the optimizing method.

Dynamic Large-Eddy Simulation of Droplet Effects on a Reacting Plume in Countercurrent Configuration

Abstract: The effects of evaporating droplets on a reacting plume have been investigated using large-eddy simulation (LES) with dynamic subgrid flow models. A countercurrent configuration, in which droplets are discharged downward toward a rising buoyant reacting plume, is used to mimic an idealized small-scale, water-based fire suppression system. Parametric studies have been conducted by varying the initial Stokes number (St 0) or nondimensional droplet size, volumetric flow rate of the spray nozzle or equivalent mass loading ratio (MLR 0), and initial droplet speed ( ), independently. The interactions between the two phases are studied in both instantaneous and statistical means. The thermal and dynamic effects of droplets on the reacting plume are scrutinized using the transport equations for the filtered (reduced) internal energy and filtered kinetic energy of the gas phase. New insights on the droplet effects have been gained by rearranging the droplet source terms in the transport equations into physically m...

TRANSPORT AND EXCHANGE OF RESPIRATORY GASES IN THE BLOOD | Root Effect: Molecular Basis, Evolution of the Root Effect and Rete Systems

Abstract: The Root effect describes the property of hemoglobins (Hbs) of some fishes such that in the presence of acid, it is impossible for the Hb molecule to be completely saturated with oxygen, even at extremely high oxygen partial pressures. The Root effect, together with a vascular countercurrent system called rete mirabile, is essential for diffusive oxygen supply to poorly vascularized fish retinas. In several fish groups the Root effect has been co-opted for oxygen secretion into the swimbladder. Structure–function analyses show that the Root effect is not an exaggerated Bohr effect of mammalian Hb but based on a different molecular mechanism. Root-effect Hb evolved before a choroid rete mirabile in the eye or a swimbladder rete mirabile and may originally have facilitated blood oxygen transport at moderate pH values, just like Bohr-effect Hb of mammals.

Probability Density Function Modeling of Multi-Phase Flow in Porous Media with Density-Driven Gravity Currents

Abstract: A probability density function (PDF) based approach is employed to model multi-phase flow with interfacial mass transfer (dissolution) in porous media The joint flow statistics is represented by a mass density function (MDF), which is transported in the physical and probability spaces via Fokker–Planck equation This MDF-equation requires Lagrangian evolutions of the random flow variables; these evolutions are stochastic processes honoring the micro-scale flow physics To demonstrate the concept, we consider an example of immiscible two-phase flow with the non-equilibrium dissolution of single component from one phase into the other-a model for solubility trapping during CO2 storage in brine aquifer Since CO2-rich brine is denser than pure brine, density-driven countercurrent flow is set up in the brine phase The stochastic models mimicking the physics of countercurrent flow lead to a modeled MDF-equation, which is solved using our recently developed stochastic particle method for multi-phase flow (Tyagi et al J Comput Phys 227:6696–6714, 2008) In addition, we derive Eulerian equations for stochastic moments (mean, variance, etc) and show that unlike the MDF-equation the system of moment equations is not closed In classical Darcy formulation, for example, the mean concentration equation is closed by neglecting variance However, with several one- and two-dimensional simulations, it is demonstrated that the PDF and Darcy modeling approaches give significantly different results While the PDF-approach properly accounts for the long correlation length scales and the concentration variance in density-driven countercurrent flow, the same phenomenon cannot be captured accurately with a standard Darcy model

Effects of Liquid Properties on CCFL in a Scaled-Down Model of a PWR Hot Leg

Abstract: This paper describes the effects of liquid properties on countercurrent flow limitation (CCFL) in a PWR hot leg. CCFL experiments were conducted in a 1/15 scaled-down model of the hot leg using air/water and air/glycerol-water solutions as working fluids. The experimental results revealed that an increase in the liquid viscosity did not change the zero liquid penetration point but did increase the slope of the CCFL curves on the Wallis diagram, which indicated that the increase in liquid viscosity from that of water did not affect the interfacial drag force but did influence the wall friction force. Numerical simulations of the experiments were carried out using a two-fluid model implemented in the CFD software FLUENT 6.3.26, and it was confirmed that the two-fluid model simulations properly evaluated the effects of liquid viscosity on the CCFL characteristics in the hot leg. Numerical simulations were also carried out to compare a low viscosity liquid to water. The predicted CCFL characteristics for low viscosity liquid showed no significant difference from those for water, which indicated that the decrease in liquid viscosity from that of water affected neither the interfacial force nor the wall friction force.

Theoretical Analysis on Film Thickness of Intertube Falling-Film Flow With a Countercurrent Gas Flow

Abstract: In falling–film type of heat exchangers, gas/vapor usually exists, and its effect on falling-film mode transitions and heat transfer could not be neglected. It could impact the film thickness, which is an important parameter to determine the thin-film heat transfer performance, or even destroy falling-film modes and significantly deteriorate the heat transfer. However, there have been very few studies of countercurrent gas flow effects on the film thickness. In this paper, the falling-film film thickness with and without liquid-gas interfacial shear stress due to the countercurrent gas flow was studied. A two-phase empirical correlation is used to solve the momentum equation. Calculation results were compared with available experimental data in literatures for validation. Reasonable agreement was achieved. Thus, the two-phase correlation for predicting shear stress of a thin film flow inside a vertical rectangular channel has been extended to a new type of flow. Effects of film Reynolds number, gas velocity, and gas-channel equivalent hydraulic diameter on the film thickness were studied. It is shown that the countercurrent gas flow thickened the falling film. The increased film thickness can shift the mode transitional Reynolds number and reduce the heat transfer coefficient, corroborating the conjecture in our earlier work.Copyright © 2011 by ASME

Gas-liquid countercurrent hydrogenation method for desulfurization, denitrification and aromatic hydrocarbon of diesel

Abstract: The invention discloses a gas-liquid countercurrent hydrogenation method for desulfurization, denitrification and aromatic hydrocarbon of diesel. Under the condition of dydrotrating diesel fractions, hydrogen and raw material diesel countercurrent pass through catalyst bed layers, wherein a reactor is divided into at least two reaction regions, and each reaction region comprises at least one hydrogenation catalyst bed layer; and the diameters of the reaction regions of the reactor are successively increased from the lower reaction region to the upper reaction region, the boundary diameter change part of at least one reaction region is provided with an effusion region, the bottom or the side of the effusion region is provided with an effusion outlet pipeline to lead the liquid of the effusion region into the lower reaction region of the reactor to be used as cooling material flow. The gas-liquid countercurrent hydrogenation method can maintain the relatively stable gas speed, prevent the flooding of the reaction regions, and enhance the operational flexibility of the reactor. Meanwhile, the gas-liquid countercurrent hydrogenation can effectively control reaction temperature, which is favorable for the arene removing reaction of the diesel fractions.

The Characteristics of Vortex Spray Countercurrent Mass Exchange Device (VSCMED)

Abstract: The article contains the results of the efficiency research of vortex dispersing countercurrent mass exchange device performance. There are recommendations given on the basis of analysis of liquid jet and liquid drops movement to assess the mass exchange surface. Processes and Equipment of Chemical and Petroleum Refineries Department of Sumy State University has carried out a great research to design new constructions of vortex mass exchanged devices with countercurrent flow of gas and drop flows.

Synchronous heat exchange gas absorption tower and nitric oxide absorption and concentration process

Abstract: The invention discloses a synchronous heat exchange gas absorption tower, which is a bubble-cap tower. The bottom of the tower is provided with a liquid outlet and a gas inlet; the top of the tower is provided with a tail gas outlet and an absorption liquid outlet; 1 to 3 layers of heat exchange coils are arranged between bubble caps of each layer of tower tray; inlets and outlets of the heat exchange coils are directly communicated with the outside of the tower; and a heat transfer medium flows in the heat exchange coils. The invention also discloses a nitric oxide absorption and concentration process by employing the synchronous heat exchange gas absorption tower. The process comprises the following steps of: mixing a NOX-containing waste gas and air according to the concentration and class of the waste gas in a certain ratio, introducing the mixed gas from the bottom of the absorption tower, introducing water or dilute nitric acid serving as an absorber from the top of the tower, performing countercurrent or crosscurrent contact reaction of the mixed gas and the absorber on each stage of filler or tower plate, timely bringing away reaction heat by using cooling water in the heat exchange coils on each stage of filler and tower plate, ensuring that the NOX concentration in the exhaust tail gas on the top of the absorption tower is 150ppm and the rate is 1kg/h, and obtaining nitric acid with the concentration of 35 to 58 percent at the bottom of the absorption tower.

Smooth heat exchanger of sewage or surface water source heat pump and system thereof

Abstract: The invention relates to a smooth heat exchanger of sewage or a surface water source heat pump and a system thereof, in particular to a heat exchanger for extracting heat or cold from the sewage or surface water by using a heat pump technology and a system thereof, belonging to the technical field of energies. The invention aims to solve the key problems of suspended matter blocking, and complex technical process, great floor area and the like which are caused by trying to realize blocking prevention in the prior art. The heat exchanger is composed of a large-diameter pipe, a pipe sheet, a shell, inner and outer partitions, closing plates, sewage or surface water inlet and outlet, clear water inlet and outlet and the like. The system is composed of the heat exchanger, a heat pump set, a water pump, connecting pipelines and the like. The sewage or the surface water can smoothly flow in the large-diameter pipe, the clear water and the sewage form countercurrent flow in the shell, and the heat pump set extracts heat from the clear water. The invention is suitable for a sewage or surface water source heat pump indirect system, and the front end does not need a filter screen or an anti-blocking device, thereby realizing continuous heat exchange and heat extraction without blocking. The invention has the advantages of simplified system and technical process, high heat exchange efficiency and small floor area.

Double-row pipeline heat exchanger

Abstract: The utility model provides a double-row pipeline heat exchanger, which comprises an external-row fin with an external-row condensation pipe and an internal-row fin with an internal-row condensation pipe The external-row fin and the internal-row have different lengths On the basis of ensuring a certain heat radiating area, the consumption of the manufacturing material is reduced so as to reduce the manufacturing cost of unit heat exchanging quantity As the amended scheme of the technical scheme, the length of the internal-row fin is the half of the length of the external-row fin The technical scheme is further improved as follows: the external-row fin is in an L shape, capable of effectively utilizing space and increasing the heat exchange efficiency in the limit space A countercurrent flow heat exchange technology is adopted; a transverse crossing technology is used for the inlet and the outlet of each flow way so as to realize the separation of the inlet and the outlet and avoid repeated heating to the greatest extent; moreover, the heat exchange efficiency is increased by the optimized design on the structure; in particular, the manufacturing cost is reduced under the premise of a certain heat exchange efficiency