Showing papers on "Countercurrent exchange published in 1985"

A New Simplified Bioheat Equation for the Effect of Blood Flow on Local Average Tissue Temperature

Abstract: A new simplified three-dimensional bioheat equation is derived to describe the effect of blood flow on blood-tissue heat transfer. In two recent theoretical and experimental studies [1, 2] the authors have demonstrated that the so-called isotropic blood perfusion term in the existing bioheat equation is negligible because of the microvascular organization, and that the primary mechanism for blood-tissue energy exchange is incomplete countercurrent exchange in the thermally significant microvessels. The new theory to describe this basic mechanism shows that the vascularization of tissue causes it to behave as an anisotropic heat transfer medium. A remarkably simple expression is derived for the tensor conductivity of the tissue as a function of the local vascular geometry and flow velocity in the thermally significant countercurrent vessels. It is also shown that directed as opposed to isotropic blood perfusion between the countercurrent vessels can have a significant influence on heat transfer in regions where the countercurrent vessels are under 70-micron diameter. The new bioheat equation also describes this mechanism.

Calculation methods for multicomponent gas separation by permeation

Abstract: Calculation methods for the single-stage permeation of a multicomponent gas mixture are presented for five flow patterns: cocurrent flow, countercurrent flow, cross flow, perfect mixing, and one-side mixing. The derivations are cast in a form suitable for computer calculation. The calculation methods presented are appropriate for systems with any number of components. Calculation results are shown for the separations of a NH3, H2, and N2 gaseous mixture by means of a polyethylene membrane, and for a H2, CH4, CO, N2, and CO2 mixture through a microporous glass membrane.

Zero‐gravity distillation utilizing the heat pipe principle (micro‐distillation)

Abstract: Separation of ethanol-water and methanol-water mixtures has been accomplished experimentally using a horizontal zero-gravity distillation column. A countercurrent flow between liquid and vapor phases was established utilizing the principle of the heat pipe. The concentration profile along the column has been investigated with various product rates. A high degree of separation was achieved in a relatively short column lined with capillary wicks. The flexible column orientation can also be a tremendous advantage as compared to the necessarily vertical operation of the conventional distillation columns.

Foam Countercurrent Chromatography Based on Dual Counter-Current System

Abstract: A novel method of performing foam separation is described. The method utilizes a gas-liquid dual countercurrent flow through a helical column subjected to a particular type of synchronous planetary motion. Samples introduced at the middle portion of the column, in either batch or continuous mode, are separated according to the foam affinity. Any material having an affinity to the foam is quickly carried with the foaming stream and eluted through one end of the column whereas other materials are carried with the liquid stream in the opposite direction and eluted out through the other end of the column. Capability of this foam countercurrent chromatographic method is demonstrated on separations of rhodamine B and Evans blue with an anionic surfactant, SDS, as a collector of rhodamine B. Successful preliminary separation of protein samples, BSA and sheep hemoglobin, indicates that the present method may be effectively applied to separation and purification of various biological samples such as enzym...

An immobilized cell reactor with simultaneous product separation. II. Experimental reactor performance.

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.

Countercurrent heat transfer device for solid particle streams

Abstract: A rotary kiln is formed by a helical tube secured inside a cylindrical shell, and fitted with flow spoiler baffles between each turn of the helical tube. Inside the helical tube, one solid particle stream flows uphill in the manner of the classical Archimedes screw. Another stream of particles is tumbled by the flow spoiler baffles and flows under gravity downhill through the center of the helical tube, tumbling over the successive convolutions of the helical tube. This downhill flow occurs because the particles collide with the interflute spoiler baffles, tumble and fall off the helical flutes, thus causing the countercurrent flow. A wide range of surface-to-volume ratios of, and heat transfer through, the helical tube may be achieved by a proper design of the relative width of the tube. This helical tube in a drum device provides heat transfer for a varied number of process applications, such as oil shale or tar sands retorting. Oil vapor is generated in one stream responsive to the heat of combustion or gasification of the spent char in the counterflowing stream. Heat from the combustion and the sensible heat of the ash is transferred through the wall of the helical tube to the inflowing stream with no stream intermixing.

Countercurrent process with froth control for treating heavy hydrocarbons

Abstract: A countercurrent technique is disclosed for contacting liquid and gas reactants in a fixed porous catalyst bed. The reactants are maintained as a multiphase mixture in the catalyst bed. Upwardly flowing dispersed gas is disengaged from liquid feedstock above the catalyst bed, while controlling froth level.

Solar energy heating system

Abstract: A solar energy system for heating water. The system comprises a solar collector, a heat exchanger, and hot water storage tank along with necessary interconnecting conduits, circulating pump and controls. The system is characterized by a double-walled fluid heating conduit within the solar collector and by a triple-walled heat exchanger housing enclosing three concentric liquid passageways. Liquid heated by the solar collector is circulated through the outermost and innermost heat exchanger passages while water to be heated is circulated in countercurrent flow through an intermediate passageway sandwiched between the other passageways.

Gas refrigeration method and apparatus

Abstract: A method of liquefying a permanent gas stream, includes the steps of reducing the temperature of the permanent gas stream at elevated pressure to below its critical pressure and performing at least two working fluid cycles to provide at least part of the refrigeration necessary to reduce the temperature of the permanent gas to below its critical temperature. Each working fluid cycle comprises work-expanding the cooled working fluid in countercurrent heat exchange with the permanent gas stream and with the working fluid being cooled, refrigeration thereby being provided for the permanent gas stream. In at least one working fluid cycle, work-expanded working fluid is brought into countercurrent heat exchange relationship with the permanent gas stream at a temperature below the critical temperature of the permanent gas and in the or each such cycle on completion of the work expansion the working fluid is at a pressure of at least 10 atmospheres.

Method for cooling normally gaseous material

Abstract: Normally gaseous feed materials, having a pressure significantly above ambient pressure, are cooled by passing the gaseous feed through an indirect heat exchange means, such as a plate-fin heat exchanger, passing a normally gaseous refrigerant, having a pressure substantially above ambient pressure, through the heat exchange means as a first stream in a concurrent direction with the feed stream, reducing the pressure of at least one second stream of refrigerant, preferably a plurality of second streams, as it exits the heat exchange means and passing the second stream of refrigerant, which has thus been reduced in pressure, through the heat exchange means in a countercurrent direction to the feed stream. This method can be employed for each cooling cycle of a method for cooling a natural gas stream to remove components therefrom and/or liquify the same.

Method for continuous countercurrent foam separation

Abstract: A method of performing foam separation utilizes a gas-liquid dual countercurrent flow through a helical column subjected to a particular type of synchronous planetary motion. Samples introduced at the middle portion of the column, either continuously or batch wise, are separated according to the foam affinity. Any material having an affinity to the foam is quickly carried with the foaming stream and eluted through one end of the column, whereas other materials are carried with the liquid stream in the opposite direction and eluted out through the other end of the column.

Cell separation with counter-current chromatography and thin-layer countercurrent distribution in aqueous two-phase system

Abstract: When mixed in aqueous solution at low concentrations the neutral polymers dextran and poly(ethylene glycol) (PEG) form a two-phase system consisting of a PEG-rich phase floating on a dextran-rich phase. These polymer phase systems have previously been shown to selectively partition cells and other particles between the phases and their interface on the basis of various surface properties of the particles. In combination with automated countercurrent techniques, partitioning in polymer phase systems gives rapid and sensitive fractionation of particle mixtures. This article contrasts separations obtained with mixtures of erythrocytes in polymer phase systems, using a nonsynchronous coil planet centrifuge (NSCPC - a version of Ito's countercurrent chromatograph) and in three different thin-layer countercurrent distribution (CCD) instruments. The result from CCD are shown to be in accord with simple theory and thus provide assistance in interpreting the theoretically complex results from the NSCPC. F...

Condensation effects in reactor transients

Abstract: Some recent results pertinent to condensation as it affects the course of light water reactor transients are reviewed. These include interfacial shear stress, local condensation heat transfer coefficients, and stability of stratified countercurrent steam/water flow. Cold-leg and combined cold- and hot-leg oscillations are also discussed. Some avenues for further research are pointed out.

Flexible tube countercurrent heat exchanger

Abstract: The countercurrent heat exchanger described here functions as a fluid heater or cooler for maintaining or modulating temperature in a liquid flowing through a glassware and plastic tube system.

Evaluation of countercurrent gas/liquid flow in parallel channels with restricted ends

Abstract: Countercurrent gas/liquid flow is examined in parallel channels interconnecting with upper and lower plenums at the upper and lower entries of a reactor core, respectively The factors controlling the countercurrent flow behavior in a single channel and multiple channels are evaluated and a method to predict flow patterns in multiple channels is developed Experiments in five parallel channels are conducted and show close agreement between predicted and experimental results

Storage water heater system

Abstract: A condensing storage water heater system comprises an inverted burner at the upper end of a water tank or cylinder connected to a vertical flueway passing through the center of the vessel. A finned heat exchanger is arranged coaxially in the flueway and the primary circuit water flowing through the heat exchanger and the products of combustion pass through the heat exchanger system in countercurrent flow. The burner and/or primary circuit flow are controlled using at least one temperature measuring device located in the storage tank so that condensation will be achieved by the heat exchanger arranged in the flueway.

Liquid phase dispersion in a packed column with countercurrent two-phase flow

Abstract: The axial dispersion in the liquid phase through a packed column was studied with air-water flowing counter-currently in a 10.16 cm inside diameter column packed with Percelain Raschig rings. The dispersion coefficient or Peclet number and mean residence time were calculated by comparing the moments of the responses measured at two points along the column. Effects of gas flow rate (0-0.37 kg/m2 sec), liquid flow rate (2.1-18.5 kg/m2 sec) and packing size (1.27,0.95,0.64 cm R.R.)on the liquid phase Peclet number and hold-up were investigated and compared with previous results.

Experimental Modeling of Steam-Water Countercurrent Flow Limit for Perforated Plates

Abstract: An experiment on steam-water countercurrent flow limit (CCFL) was performed using perforated plates with variations of hole size, hole edge chamfer and plate thickness. The results show that coefficients in existing countercurrent flow correlations depend on those geometry variations. Based on the observations of the flow through a plate, a simple model for the estimation of countercurrent flow was derived. The model contains a parameter which is only dependent on plate geometry. The model was applied to experiment results from several plate geometries and closely predicted not only the CCFL for experiments performed during this work but also for other experiments performed with a larger size perforated plate.

Device for the exchange of heat energy between air flows for recovery of ventilation heat

Abstract: Approximately 80% of the energy requirement for the heating of residential buildings arises from transmission and approximately 20% from ventilation. The invention envisages recovering a part of the ventilation heat. To this end, the joints on external windows and external doors are extensively sealed and the cold outside air flowing in is conducted, via a heat exchanger according to Figure 1, past the warm room air flowing out. During this, the outside air flowing in is heated. The heat-energy saving amounts to approximately 50% of the ventilation heat or approximately 10% of the overall heating energy. According to the embodiment of the invention, it can be built into window wings, window frames, wall or door elements. It can be designed as a co-current, countercurrent or crosscurrent heat exchanger. The flow drive can take place by wind pressure, lift or mechanically.

Stability of steam-water countercurrent stratified flow

Abstract: Two flow instabilities which limit the normal condensation processes in countercurrent stratified steam-water flow have been identified experimentally: flooding and condensation-induced waterhammer. In order to initiate condensation-induced waterhammer in nearly horizontal or moderately-inclined steam/subcooled-water flow, two conditions, the appearance of a wavy interface and complete condensation of the incoming steam, are necessary. Analyses of these conditions are performed on a basis of flow stability and heat transfer considerations. Flooding data for several inclinations and channel heights are collected. Effects of condensation, inclination angle and channel height on the flooding characteristics are discussed. An envelope theory for the onset of flooding in inclined stratified flow is developed, which agrees well with the experimental data. Some empirical information on basic flow parameters, such as mean film thickness and interfacial friction factor required for this theory are measured. The previous viewpoints on flooding appear not to conflict with the present experimental data in nearly horizontal flow but the flooding phenomena in nearly vertical flow appear to be more complicated than those described by these viewpoints because of liquid droplet entrainment.

Slugging of countercurrent gas-liquid flow in a horizontal channel.

Abstract: Slugging of countercurrent stratified air-water flow has been investigated in horizontal and in nearly horizontal channels. The tests were performed in the rectangular channels, 35 mm wide and 3 m long. Three channel depths, 25, 35, and 60 mm, were employed. The onset of slugging in the channel inclined to keep a constant liquid level in the channel was compared with that in the horizontal one. Independent of the channel depth and the channel slope. All the data correlated with the relation between the gas velocities relative to the interfacial wave celerity and local gas channel depth. Comparing with cocurrent flow, the relative gas velocities at slug formation were high. It is presumed to be caused by the difference in the shapes of interfacial waves. The deflection of liquid level in horizontal countercurrent stratified slow was also examined by means of the principle of minimum entropy production.

High efficiency column crystallizer

Abstract: An improved countercurrent solid-liquid contacting apparatus, and more particularly an improved counter-current crystallizer column is disclosed. The present invention embraces the discover that column efficiency and product purity can be substantially enhanced by reducing axial liquid back-mixing by using stationary solid beds and transport means at spaced intervals along the column length.

Flat plate heat exchanger

Abstract: IMPROVED FLAT PLATE HEAT EXCHANGER This disclosure relates to an improved parallel plate heat exchanger characterized by a laminated sandwich of flat plates and flow-directing baffles so designed and arranged as to divide an incoming flow of two fluids into a plurality of discrete portions and simultaneously pass all the portions of one fluid in countercurrent heat exchange relation to the portions of the second fluid as they migrate between inlets and outlets at opposite ends thereof. The disclosure also encompasses the construction wherein the baffles cooperate with integrally-formed dimples in the plates to maintain the latter in spaced relation and produce the fluid flow paths therebetween.

Packing element for mass and heat transfer columns

Abstract: The invention relates to a mounting element for material or heat exchanging columns in gas and / or liquid flows, especially in a countercurrent process, such as those used for distillation, distillation and absorption towers. Here Components for these purposes are to be created, which are further enhanced at low pressure losses, the efficiency and which also permit an inexpensive production. For this purpose, the lamellae are interspersed with slots, which slots are preferably arranged parallel to each other, optionally added, and and the form tabs to each other without contact. These slots act as capillaries and distort the impinging drops, thus increasing, inter alia, the surface wetting.

Hydrolysis of lignocellulosic material

Abstract: A continuous hydrolysis process for the hydrolysis of wood or other lignocellulose material into sugars and other products has an overall countercurrent flow of liquids and solids but an integral co-current flow of the liquids and solids as part of the process. As shown in Figure 2, woodchip or other feedstock is formed into a slurry which is acidified, pressurised and heated before being hydrolysed in reactors J. Three heat exchangers L1, L2 and L3 form a closed circuit in which exchanger L2 recovers heat from the slurry, L1 returns heat to the slurry and L3 makes up lost heat. The slurry is cooled before pressure reduction by pressure reducing means N and separation of the solids and liquid. The cooling prevents flashing to steam of part of the liquid in the slurry so that the process is single phase where generation of steam is avoided. After separation the solids can proceed to further processing or to discharge as lignin as indicated by arrow B. The liquid can proceed to further processing or discharge as indicated by arrow D.