Axial Flow Rate Research Articles

Heat-transfer characteristics of fluid flow in an annulus with an inner rotating cylinder having a labyrinth structure

The heat transfer coefficient of fluid flow was experimentally investigated in an annulus with an inner rotating cylinder to estimate thermal fatigue of the inner and outer cylinders on the rotating machine. Following three points were found in the study. (1) Within the range of the experimental conditions, the heat transfer coefficient did not depend on the axial flow rate, rather it had a large dependence on the inner cylinder rotating speed. (2) The heat transfer coefficient at the top of the labyrinth was about three times as larger as that at the bottom. (3) An empirical correlation equation considering the gap between the inner and outer cylinders was proposed, which predicted the heat transfer coefficient on the rotating machine within ±30%.

Oscillatory flow of a viscous fluid through converging-diverging orthotropic tethered tubes

A theoretical investigation of the propagation of pressure waves through uniformly converging and diverging thin-walled orthotropic elastic tubes filled with a Newtonian fluid is made in this paper, by considering the flow to be laminar and unsteady. Axisymmetric solutions of the differential equations that govern the motion of the fluid and the solid elastic wall are obtained. The outer surface of the wall is taken to be free of tractions. By using the solutions, a complicated form of transcendental equation is derived, that serves as a dispersion equation and puts forth a relation between the frequency and the wave number. This equation is solved by employing both analytical and numerical techniques. Numerical values of the pressure gradient, mean axial velocity, radial velocity, flow rate, amplitude ratio, phase velocity, and wave length have been computed for different angles of taper for a particular situation. It is felt that the results presented in the paper will find adequate applications in the study of blood flow through certain arterial segments, particularly in investigating the propagation of small amplitude harmonic waves, generated due to the flow of blood when the wave length is large compared to the radius of the arterial segment.

FLUID DYNAMICS IN A TUBULAR MEMBRANE: THEORY AND EXPERIMENT

Abstract Measurements of trans-cartridge [axial] pressure drops for pure liquid flowing in a porous tube under all regimes of flow as a function of wall suction and axial flow rate are reported. At very low axial flow rates [ReF 1,000], low values of wall suction [ReW 0.25] have a minimal effect on the non-dimensional axial pressure drop. At very high axial flow rates [ReF20,000], however, all values of wall suction have a minimal effect on the axial pressure drop, Wall suction, on the other hand, has its maximum effect on the axial pressure drop at intermediate axial flow rates [1,000 ReF15,000]. It is in this range that most commercial membrane modules operate. Starting with the equations of continuity and Navier-Stokes we have developed two relatively simple approximate analytical solutions of this problem. The first approach assumes an average constant wall flux and includes the effect of the inertial terms while the second approach accounts for axial pressure-dependent flux but neglects the inert...

The reduction of thermal nitrogen oxides (NOx) emission using staged combustion in furnace

The experimental study described in this paper is to investigate the control of thermal nitrogen oxides emissions from a 2.28 MW gas-fired test furnace. Tests, including changing axial or radial air flow rate, adding cooling water, and adding staged air, were performed to characterize and optimize the fuel-rich burning zone and the fuel-lean burnout zone independently. Detailed measurements of O2, CO2, CO, NO and NOx were made at the fuel-rich burning zone and furnace exit. The influence of forming CO, NO and NOx was examined. Results indicated that adding staged air in the fuel-rich burning zone (75 cm from burner) will reduce the maximum NO and NOx emissions. Adding cooling water in a right position may further lower the NO and NOx emissions. In addition, the least formation of thermal nitrogen oxides in the first stage fuel-rich burning zone will occur at the stoichiometric ratio’s inverse value, (φ1)−1, 0.65 to 0.7.

GAS FLOW BEHAVIOUR IN SPRAY DRYER

ABSTRACT Gas flow behaviour in co-current spray dryer is investigated numerically using the k-ε model of turbulent flow.The calculated flow fields are compared with previous experimental results. The distributions of the time average velocity and the intensity of turbulence are in good agreement for both values. The main flow region in the dryer is almost coincident each other. The main (axial) flow rate increases remarkably by acompanying the recirculation flow in the axial direction of the dryer. which reaches a maximum value of about 1.7 times the inlet flow rate. The particle trajectories obtained in the calculated gas flow fields are influenced colisiderably by the recirculation flow.

Leakage effects in laminar duct flow: a numerical study

The influence of transverse leakage into a pressure-driven laminar flow in an infinitely long square duct is investigated. By a simple decomposition of the resulting three-dimensional pressure field, the leakage-induced secondary flow problem decouples from the primary flow problem. The numerical study reveals that two qualitatively different secondary flow patterns may occur, depending on the leakage flow rate. For a given streamwise pressure gradient it is observed that the axial mass flow rate may reduce by about 30 percent under certain leakage conditions, accompanied by a corresponding 50 percent increase in the Darcy-Weisbach friction factor.

Membrane distillation in the textile wastewater treatment.

Membrane Distillation has been used to produce pure water and to concentrate various kind of solutions at saturation conditions or to separate alcohol-water solutions. Recently this process has been used in the wastewater treatment i.e. to produce pure water and to recovery chemicals from textile wastewater treatment. In this work the experimental analysis of dye solutions treatment has been carried out. Distillate flux and purity, concentration factor and temperature polarization coefficients (TPC) have been measured and their functionalities as function of temperatures and axial flow rate have been analysed. Finally, the energy efficiency (EE) of the experimental system has been evaluated and the potentiality of these applications has been estimated.

Protein overproduction in Escherichia coli: RNA stabilization, cell disruption and recovery with a cross-flow microfiltration membrane

After optimizing overproduction of a heterologous gene product (chloramphenicol acetyltransferase, CAT) using an RNA stabilization vector ∗ ∗ Patents pending. in Escherichia coli (Chan et al., 1988), a single step cell disruption and recovery method ∗ for obtaining a product stream essentially free of cell debris was developed. The behavior of an RNA stabilization plasmid (pKTN-CAT) containing stabilizing intron RNA was investigated in two different media both in batch and chemostat modes. CAT production of pKTN-CAT was consistently higher (3- to 7-fold) than that of the control lacking the stabilization sequences (pK-CAT). Highest CAT production was observed for cells grown in minimal medium in batch mode and induced for CAT expression early in growth. CAT production of cells grown in the chemostat mode exhibited an optimal dilution rate of about 0.1 h −1. Enhancement of protein production by pKTN-CAT as compared to pK-CAT tended to be higher when grown in rich medium rather than in minimal medium. Presence of the RNA stabilization plasmid did not significantly alter the growth rate of the cell. Using a combination of chemical treatment (1 mM EDTA) and shear stress resulting from cross-flow in a stainless steel microfiltration membrane ∗ , CAT was released into the medium through disruption of the E. coli cells. The permeate flux increased from 2000 to 9000 kg m −2 h −1 with increasing axial Reynolds number from 10,000 to 60,000 or increasing mean shear stress from 12 to 47 Pa. The turbidity of the permeate was approximately 4% that of the retentate over this range of axial flow rates, indicating excellent removal of cell debris. Also, the concentration of CAT in the permeate was equal to that in the retentate over this range of axial flow rates, indicating complete passage of protein through the membrane. Thus, using a combination of chemical treatment and fluid-induced shear stress in a cross-flow membrane module, we were able to disrupt and recover the heterologous protein in a stream low in debris.

Time-resolved velocities and turbulence in the oscillating flow of a pulse combustor tail pipe

The cyclic behavior of the oscillating velocity field in the tail pipe of a pulse combustor was studied using laser doppler velocimetry. In this flow, the oscillations result from an acoustic resonance and have amplitudes of up to 5 times the mean velocity. Oscillation frequencies were varied from 67 to 101 Hz. Streamwise velocity and turbulence-intensity boundary layer profiles were measured to within 130 μm of the wall, and transverse turbulence measurements were made to within 2 mm. The phase relationships of the velocity, turbulence intensity, and combustion chamber pressure oscillations are compared. Velocity oscillations near the wall are found to phase lead those in the center of the pipe, creating periodic flow reversals through the boundary layer. A comparison is made between this turbulent oscillating boundary layer and the laminar oscillating boundary layer for flow over a flat plate. The effects of axial position, pulsation frequency, pulsation amplitude, and mean flow rate on the velocity and turbulence profiles are discussed. Time-resolved wall shear stresses (directly calculated from the velocity measurements) are presented and compared with those of steady turbulent flow. Time-averaged velocity and turbulence profiles are also compared with those of conventional steady turbulent flows. The time-averaged velocity profile is found to be flatter than that of steady flow at the same mean Reynolds number, and both the streamwise and transverse turbulence intensities are found to be significantly higher than those of steady flow.

Axial and Circumferential Film Flow Rate Prediction in a Horizontal Annular Two-Phase Flow Using the FIDAS-3DT Code

Prediction of developing and transient characteristics of circumferential and axial film velocities in a horizontal annular two-phase flow is carried out with the FIDAS-3DT computer code developed in Japan that can provide three-field representation in subchannel flow using the full conservative equations and simple constitutive relations. The specifications are those from a reported air-water experiment in a 3.9m by 32mm diameter pipe. Steady, fully developed axial flow rates seem to be over-predicted compared to the experimental results. A corrective procedure is suggested which takes into account the radial variation in the axial velocity profile.

Analysis of a rotating annular reactor in the vortex flow regime

A theoretical analysis of a vortex flow reactor is presented. Consecutive (first order) reactions taking place on the inner rotating surface are considered. The concentration profiles of the various species, conversions and yields are obtained along the reactor for low axial flow rates, corresponding to high residence times. The induced vortical flow, obtained due to an imposed rotation imparted on an axial annular flow, is utilized to improve the conversion and yield of diffusion controlled (fast) reactions. Comparison of the performance of the vortex flow reactor with that operated without rotation, utilizing only laminar axial flow, indicates enhanced conversions and yields due to the axially convected vortices through the reaction chamber. The extent of the augmented mass transfer has been explored by the corresponding mass transfer coefficients correlated with rotation.

Cross‐flow membrane microfiltration of a bacteriol fermentation broth

Although cross-flow membrane filtration is a very attractive option for harvesting cells and recovering enzymes from cell homogenates, the process is not without its problems. Foremost of these is the deposit of dissolved and suspended solutes onto the membrane surface during operation. The formation of these dense and sometimes compressive sublayers (often called cakes) offers additional resistance to axial and permeate flows and often affects the retention characteristics of the process. In view of the complex nature of the sublayer formation process and its sensitivity to cross-flow velocity, this investigation was undertaken to determine the main factors responsible for the decline in performance during the harvesting of B. polymyxa broth by membrane microfiltration. System parameters varied include axial flow rate, concentration of cells, proteins and other components in the feed, membrane materials (ceramic, polypropylene, and stainless steel), and cleaning methods. To help explain the observed results, a new mass transport model-the solids flux model-based on the assumptions that back migration of particles from the sublayer or membrane surface is negligible and that particles that reach the solid-solution interface attach (stick) completely, is tested. Using a variety of diagnostic methods, magnesium ammonium phosphate precipitate is formed during steam sterilization of the medium and is implicated as the major foulant in this study.

Pressure Flow of Non-Newtonian Fluids between Eccentric Double Cylinders with the Inner Cylinder Rotating

The authors experimentally observed the pressure flow of non-Newtonian fluids between eccentric double cylinders with the inner cylinder rotating. Experiments were carried out to measure the pressure gradient, the angle of the secondary flow region and the pressure distribution on the outer cylinder using aqueous solutions of hydroxy ethyl cellulose (HEC:). Results are summarized as follows:1) Axial flow rate was enhanced by the rotation of inner cylinder. Denote the axial flow rate Qs; and Qr; respectively with the inner cylinder stationary and rotating. Then the larger was the difference between Qs; and Qr; the larger was the effect of eccentricity.2) The angle of the secondary flow region increased with decreasing number of inner cylinder rotation and increasing axial pressure gradient.3) Distribution of pressure on outer cylinder was affected by the axial flow rate, radius ratio and eccentricity.4) Experimental results agreed well with numerical predictions. Thus the reliability of the numerical method used in the previous paper was confirmed.

A Method of Determination of Some Rheological Characteristics of Viscoelastic System

The study concerns the unsteady flow of viscoelastic fluids in rigid cylindrical tubes, where one of the ends is either open or submerged in a viscoelastic sink. This shows the possibilities offered by analysis of axial speed or flow rate measurements and by pressure gradient measurements. In both cases, the model serves as a “rheometer” and allows the properties of the fluid to be determined automatically; in the second case, knowledge of the behavior of the fluid and use of axial speed analysis enables rheological modeling of the sink to be effected. This possibility allows “remote” investigations of complex mechanical systems to be done, and leads to numerous applications in various areas.

Design and application of a borehole flowmeter

Abstract A borehole flowmeter has been developed to measure low flow rates in NX (76 mm) boreholes. The instrument can be used to determine the standing water level and permeability of a test section of the borehole. The borehole flowmeter is a short, lightweight wireline packer which is inflated pneumatically and contains a turbine flowmeter transmitter unit. The useful flow range of the standard instrument is approximately 0.7 cm 3 /s to 70 cm 3 /s. The unit was originally designed to measure small axial flow rates in an array of boreholes which was thought to intersect a series of perched aquifers. Experimentation showed that an increased rate of flow could be induced through the unit by piping water into the top of the borehole, the flow rate being proportional to the excess head of water above the unit. Using this principle, a form of in situ falling head permeability test was devised. The corrected head of water at a zero flow rate was found to correspond to the standing water level in a borehole, and the linear relationship between applied head and flow rate was used to calculate the permeability of the section of borehole below the unit. The results are compared with those of packer tests carried out in the same test sections. The method has several advantages over packer testing in many conditions. The wireline equipment is light and can be operated by one man. The permeability test results are repeatable and are completed on average within one hour, though a satisfactory relationship between flow and head is usually established within ten minutes in a moderately permeable formation.

An Analysis of the Circumferentially Grooved Journal Bearing with Consideration of Lubricant Film Reformation

An analysis of a central, circumferentially grooved journal bearing has been undertaken. As well as considering the rupture of the lubricant, detailed attention has been paid to film reformation. A computer program has been developed which automatically locates the cavitation region without manual intervention and the numerical analysis technique developed to do this is fully described. Results for the steady state and dynamic performance characteristics of the bearing are presented and predictions compared with other published work where possible. The effect of not considering the reformation of the lubricant film is examined and it is concluded that satisfactory predictions of performance can be obtained for all parameters except the axial flowrate.

Virus Concentration from Water Using High-Rate Tangential-Flow Hollow Fiber Ultrafiltration

The efficacy of tangential flow hollow fiber Ultrafiltration (TFHFU) as a means of concentrating poliovirus 2 (Sabin) from large volumes of tap water was studied. Initially, hydrodynamic studies using 50-1 tap water feed solutions were conducted to evaluate transmembrane flux as a function of axial flow rates (or Reynold's numbers, Re). With increasing Reynold's number, flux-decline rates were reduced. As a result, experimental duration was shortened from 110 min at Re=300 to 30 min at Re=1728. In all cases, radial flow was assisted by a vacuum force applied to the outside of the hollow fibers. Virus recovery capability was evaluated using 20-, 50-, and 100-1 feed samples seeded with poliovirus 2 from 604 to 0.5 pfu/ml. All virus experiments were conducted at Re=1728 and a vacuum force of 3.27 × 104 Pa. The mean duration of the 20-, 50-, and 100-1 experiments was 13, 42, and 79 minutes, respectively. The overall average virus recovery from all experiments was 69.1 ± 24.6%. In operating the tangential-flow hollow fiber ultrafiltration module in its normal recycle-mode with low turbidity waters (<10 NTU), the expected steady flux-decline resulting from membrane fouling was not observed. Instead, the transmembrane permeation flux was maintained at a relatively constant value especially near the end of the experiments when the solute concentration in the feed increased the fastest. Increased feed water temperature resulting from the addition of pumping energy during recycle is responsible for this unexpected advantage. Final temperatures never exceeded a point at which virus inactivation would occur. For high turbidity feed waters (75 to 85 NTU), obtained by the addition of kaolin clay, virus recoveries varied from 30 to 49%, Final turbidities at the termination of a 50-1 run were from 950 to >1000 NTU. In spite of the high turbidity, the mean experiment duration for dehydrating 50 liters of turbid feed water was 39 minutes; approximately the same as for the low-turbidity tap water runs.

Circumferential wall temperature variations in horizontal boiler tubes

The design of horizontal boiler-tube arrays, for both fluidized bed combustors and conventional power plants, is today constrained by the uncertainty in the circumferential wall temperature profile prevailing in the tubes. High circumferential anisothermality at elevated temperatures can lead to high thermal stress and threaten both the load carrying and operating life of steam-generating boiler tubes. A critical review of the available results and a detailed analysis of two-phase flow regimes in boiler tubes appear to indicate that a reduced circumferential temperature difference is associated with transition from intermittent to annular flow, rather than the termination of stratified flow. The two-phase flow regime analysis is, furthermore, shown to successfully predict the axial variation and flow rate dependence of circumferential anisothermality.

An unsteady-state analysis of the hemofiltration processes

Postdilutional hemofiltration might be an interesting alternative to the more classical hemodialysis. Concentration polarization phenomena play, however, a significant role in this process. The possibility of increasing ultrafiltration fluxes by inverting axial flow rate on the pressurized membrane face has been theoretically investigated in this paper. A new analytical procedure has been applied which offers the possibility of calculating concentration profiles in the system investigated. This analysis shows that the axial now inversion might be advantageous in systems where the axial flow is a limiting condition, and the axial velocity is a less limiting factor.

HEAT TRANSFER IN A VERTICAL, LIQUID‐FULL SCRAPED‐SURFACE HEAT EXCHANGER. APPLICATION OF THE PENETRATION THEORY AND WILSON PLOTS MODELS

ABSTRACTHeat transfer characteristics of a scraped‐surface heat exchanger (Contherm Model 6 × 2) were evaluated at ultra high temperatures using water and soybean water extracts as model systems. The resistance equation was used to calculate internal (scraped‐side) heat transfer coefficients (hi) from the overall heat transfer coefficient, the wall coefficient and the external (steam‐side) coefficient (calculated from the Nusselt Theory using an iteration procedure). The Penetration Theory of Harriot (1958) predicted hi values quite well at low axial mass flow rates, where laminar flow conditions prevail. However, turbulent axial flow resulted in experimental higreater than predicted by the theory. A correction factor based on Prandtl number suggested by Trommelen et al. (1971) did not improve the prediction. The Wilson Plots method was useful for explicitly accounting for axial and rotational velocity effects, both of which significantly affected heat transfer, especially at high values of either variable.