Wide Range Of Flow Rates Research Articles

A collection of experimental data for aerosol monitoring cyclones

ABSTRACTCyclone behavior is complex and difficult to model. Recent years have seen the development of new and better predictive models for cyclone performance, which are providing new insights into how cyclone performance is affected by cyclone geometry. Experimental data are essential for verification of such models. In this article we present a dataset of more than 250 experimental determinations of cyclone penetration. The dataset includes cyclones with a wide range of sizes and geometries, tested at a wide range of flow rates. We illustrate some empirical, semi-empirical and mathematical approaches to modeling these cyclone data. For our data, we show that mathematical modeling approaches developed for large gas-cleaning cyclones can also be applied to small aerosol monitoring cyclones, to diverse cyclone geometries, and laminar flow operating conditions.Copyright © Crown copyright

Flow of yield stress and Carreau fluids through rough‐walled rock fractures: Prediction and experiments

AbstractMany natural phenomena in geophysics and hydrogeology involve the flow of non‐Newtonian fluids through natural rough‐walled fractures. Therefore, there is considerable interest in predicting the pressure drop generated by complex flow in these media under a given set of boundary conditions. However, this task is markedly more challenging than the Newtonian case given the coupling of geometrical and rheological parameters in the flow law. The main contribution of this paper is to propose a simple method to predict the flow of commonly used Carreau and yield stress fluids through fractures. To do so, an expression relating the “in situ” shear viscosity of the fluid to the bulk shear‐viscosity parameters is obtained. Then, this “in situ” viscosity is entered in the macroscopic laws to predict the flow rate‐pressure gradient relations. Experiments with yield stress and Carreau fluids in two replicas of natural fractures covering a wide range of injection flow rates are presented and compared to the predictions of the proposed method. Our results show that the use of a constant shift parameter to relate “in situ” and bulk shear viscosity is no longer valid in the presence of a yield stress or a plateau viscosity. Consequently, properly representing the dependence of the shift parameter on the flow rate is crucial to obtain accurate predictions. The proposed method predicts the pressure drop in a rough‐walled fracture at a given injection flow rate by only using the shear rheology of the fluid, the hydraulic aperture of the fracture, and the inertial coefficients as inputs.

Simulation of a Diesel Engine with Variable Geometry Turbocharger and Parametric Study of Variable Vane Position on Engine Performance

Modelling of a turbocharger is of interest to the engine designer as the work developed by the turbine can be used to drive a compressor coupled to it. This positively influences charge air density and engine power to weight ratio. Variable geometry turbocharger (VGT) additionally has a controllable nozzle ring which is normally electro-pneumatically actuated. This additional degree of freedom offers efficient matching of the effective turbine area for a wide range of engine mass flow rates. Closing of the nozzle ring (vanes tangential to rotor) result in more turbine work and deliver higher boost pressure but it also increases the back pressure on the engine induced by reduced turbine effective area. This adversely affects the net engine torque as the pumping work required increases. Hence, the optimum vane position for a given engine operating point is to be found through simulations or experimentation. A thermodynamic simulation model of a 2.2l 4 cylinder diesel engine was developed for investigation of different control strategies. Model features map based performance prediction of the VGT. Performance of the engine was simulated for steady state operation and validated with experimentation. The results of the parametric study of VGT’s vane position on the engine performance are discussed.

Numerical simulation and experimental study on a deoiling rotary hydrocyclone

In this study, the internal flow field and oil-water separation performance of a rotary hydrocyclone (RH) were investigated using computational fluid dynamics (CFD) simulations and experimental methods. In the numerical simulation, the turbulence was modeled by Reynolds stress model; the oil-water two-phase flow was modeled using the Algebraic Slip Mixture model; and the rotating walls were modeled by Multiple Reference Frame method. The numerical results were consistent with the experimental results. The influences of pipe wall rotation speed and inlet flow rate were also investigated. The results demonstrate that both rotation speed and flow rate have significant impacts on the velocity profile; increasing rotation speed or decreasing flow rate decrease the pressure drop and increase separation efficiency. The presence of oil core was predicted by the numerical calculations and observed in the experiment. In conclusion, the results indicate that the newly designed RH is a separator with high efficiency and wide flow rate range.

CFD analysis of a novel modular manifold with multi-stage channels for uniform air distribution in a fuel cell stack

Multiple fuel cells are generally connected in series or in parallel to supply a sufficient power output. Uniform distribution of hydrogen and air supplied to each individual fuel cell is a critical challenge, because the performance of a stack is limited by the single cell which receives the minimum amount of reactants. Various manifolds have been investigated in order to improve the flow distribution uniformity between individual fuel cells in a stack. However, a satisfactory uniformity is hard to obtain, and the existed manifolds are difficult to scale up. Therefore, a tree-type modular manifold is designed and optimized in the present study. Two different channel dimensions are compared regard to air flow distribution uniformity and overall pressure loss. The effects of channel length and air flow rate on the uniformity and pressure drop are studied by CFD simulation. The results show that an air flow uniformity around 0.99, which is the highest value reported in the literature, can be achieved in a wide range of air flow rate for a single fuel cell. The scale-up method by integrating several modular manifolds with a customized manifold to distribute air for larger fuel cell stacks is also explained.

Effects of viscosity ratio, interfacial tension and flow rate on hysteric relative permeability of CO2/brine systems

It is essential to understand the relative permeability of CO2 and brine when characterizing the flow of CO2 as it is injected into an aquifer. The relative permeability of CO2 and brine has a significant impact on CO2 migration and saturation distribution. This paper presents the results of experimental investigations into the effects of the viscosity ratio and interfacial tension (IFT) on steady-state relative permeability. A series of unsteady-state experiments were conducted with a wide range of flow rates. These enabled us to determine the low end-points of the relative permeability and high residual brine saturation of the two-phase CO2/brine system.The results clearly show that the steady-state relative permeability depends on the viscosity ratio and IFT of the CO2/brine system. Due to the low CO2 viscosity and flow rate, the residual saturation of brine is greater than 50%. The low end-point of the relative permeability of CO2 is associated with small viscous forces. In the CO2/brine system, these forces are normally smaller than the capillary force. The small viscous forces are caused by the injected CO2 having a much lower viscosity than brine. The viscous force increases with increasing flow rate, resulting in more efficient CO2 displacement.

Design, simulation, and characterization of a radial opposed migration ion and aerosol classifier (ROMIAC)

We present the design, simulation, and characterization of the radial opposed migration ion and aerosol classifier (ROMIAC), a compact differential electrical mobility classifier. We evaluate the performance of the ROMIAC using a combination of finite element modeling and experimental validation of two nearly identical instruments using tetra-alkyl ammonium halide mass standards and sodium chloride particles. Mobility and efficiency calibrations were performed over a wide range of particle diameters and flow rates to characterize ROMIAC performance under the range of anticipated operating conditions. The ROMIAC performs as designed, though performance deviates from that predicted using simplistic models of the instrument. The underlying causes of this non-ideal behavior are found through finite element simulations that predict the performance of the ROMIAC with greater accuracy than the simplistic models. It is concluded that analytical performance models based on idealized geometries, flows, and fields should not be relied on to make accurate a priori predictions about instrumental behavior if the actual geometry or fields deviate from the ideal assumptions. However, if such deviations are accurately captured, finite element simulations have the potential to predict instrumental performance. The present prototype of the ROMIAC maintains its resolution over nearly three orders of magnitude in particle mobility, obtaining sub-20 nm particle size distributions in a compact package with relatively low flow rate operation requirements.

Magneto-Hydrodynamic Fractionation (MHF) for continuous and sheathless sorting of high-concentration paramagnetic microparticles.

Sorting cells, microorganisms and particles from a solution is of paramount importance in many biological applications. An ideal sorting device should work at high throughput, involve simple design, avoid energy consumption, operate without a diluting sheath flow and perform separation with high purity. However, currently available sorting methods such as pinched flow fractionation, hydrodynamic filtration, magnetophoresis and deterministic lateral displacement meet only a few of the above-mentioned characteristics. In this paper, we report a hybrid technique combining magnetic focusing of particles in a thin microchannel and their hydrodynamic fractionation at a downstream expansion region, to devise a sheathless and high-throughput Magneto-Hydrodynamic Fractionation (MHF) method. First, sheathless magnetic focusing of 11μm microparticles against the wall of the thin microchannel was investigated over a wide range of flow rates (0.5-5mL h-1). Then, a mixture of 5μm and 11μm paramagnetic particles was injected into the device at a flow rate of 5mL h-1 to demonstrate their sorting. Both of these magnetic particles were aligned along the wall of the channel and hence focused in the device, however their centers were lying on different streamlines due to their different sizes. Therefore, they were separated into distinct streamlines upon entering into the expansion region. Using this device, we achieved a high throughput sorting of more than 104 particles per second with an approximate on-chip fractionation purity of 98%. This technique has a great potential for separation of more than two magnetic particles for application in immunomagnetic affinity-based sorting of multiple biological substances.

Deformation of an elastic capsule in a microfluidic T-junction: settling shape and moduli determination

Microdevices involving a stagnation-point flow, such as cross- and T-junctions, are useful for particle manipulation and characterization. In contrast to the wide use of cross-junctions, T-junctions have received limited attention as a medium for capsule deformation and characterization. In the present study, we investigate computationally the settling shape of an elastic capsule in a T-junction microchannel for a wide range of flow rates. Our work reveals that the capsules show a rich deformation behavior including (inverse) swallow-cap, sit-on and whitewater kayak shapes. We also propose a new methodology for the simultaneous and accurate determination of the shear and area-dilatation moduli of the membrane of artificial capsules via a single experimental technique by utilizing the dependence of the settling capsule’s dimensions on the capillary number and the membrane hardness identified in our investigation. Our moduli methodology utilizes high flow rates (i.e., large capsule deformations) where the effects of the membrane hardness become prominent and thus capsules with different area-dilatation modulus can be identified. Our procedure has the additional advantage of not being influenced by the fluids’ viscosity ratio or the membrane viscosity.

Hybrid Flow Battery/Mediator Supercapacitor Using Iron Cyanide Redox Materials

Flow batteries have very high specific energy but low specific power and slow response while mediator supercapacitors give high specific power and fast response but relatively low specific energy. A hybrid flow-battery/supercapacitor is fabricated and operated under different conditions in order to provide both high specific energy and power. The porous electrodes of the consisted of catalysts for redox reactions (Ni, Pt, Ru, etc.), mediators (NaI/I2, VOSO4, K4Fe(CN)6, etc.), and polymer electrolytes as binders. An ion exchange membrane was used as the separator. An array of complex iron cyanide compound were synthesized and used as the redox materials in slurry reservoirs. This investigation focuses on the effects of flow rate, temperature, pressure, and mediator concentration on the performance of the energy storage device. Cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) measurements were conducted under a wide range of flow rate and mediator concentration. The redox potential of the slurry was monitored using an electrochemical redox sensor. The electrochemical kinetics of the mediators and redox materials were evaluated using linear polarization methods. The results indicate that at a given scan rate for CV or current for GCD, both flow rate and mediator concentration greatly impact the charge/discharge behaviour, the total energy, and efficiency. There is a critical flow rate at which a capacitor-like behaviour transits to battery-like behaviour. A simple numerical model is created to analyse the experimental data and provide an explanation of the observations.

Hydrocyclone equivalent settling area factor at higher concentrations and developing a performance chart

Abstract The equivalent settling area factor allows for comparison amongst different centrifuge separators. For hydrocyclones, the so far developed factor does not consider the effect of concentration of solid particles c in the feed stream, because particle interactions at high concentrations cause hindered settling and reduce hydrocyclone performance. The focus of this paper is a modification of this factor to allow prediction of the influence of higher particle concentration in the feed stream. In particular, the equivalent area factor is modified at high particle concentration by applying different forms of hindered settling concentration functions and using data obtained from experiment or from existing empirical correlations. This results in a set of modified models that are evaluated using statistical techniques. Through statistical analysis, the function f ( c ) = c 0.0488 exp ( - 9.445 c ) is selected to modify the equivalent settling area for hydrocyclones. A performance chart is developed for hydrocyclones by undertaking the modified equivalent area model that can be used in hydrocyclone design applications. The developed performance chart is validated and is shown to be capable of predicting the hydrocyclone performance over a wide range of hydrocyclone flow rates and separation cut sizes. This chart is compared with a performance chart available in the literature and the chart in the literature is shown to over-predict the hydrocyclone performance.

Highly integrated polymeric microliquid flow controller for droplet microfluidics

Microfluidic applications demand accurate control and measurement of small fluid flows and volumes, and the majority of approaches found in the literature involve materials and fabrication methods not suitable for a monolithic integration of different microcomponents needed to make a complex Lab-on-a-Chip (LoC) system. The present work leads to a design and manufacturing approach for problem-free monolithic integration of components on thermoplastics, allowing the production of excellent quality devices either as stand-alone components or combined in a complex structures. In particular, a polymeric liquid flow controlling system (LFCS) at microscale is presented, which is composed of a pneumatic microvalve and an on-chip microflow sensor. It enables flow regulation between 30 and 230 μl/min with excellent reproducibility and accuracy (error lower than 5%). The device is made of a single Cyclic Olefin Polymer (COP) piece, where the channels and cavities are hot-embossed, sealed with a single COP membrane by solvent bonding and metalized, after sealing, to render a fully functional microfluidic control system that features on-chip flow sensing. In contrast with commercially available flow control systems, the device can be used for high-quality flow modulation in disposable LoC devices, since the microfluidic chip is low cost and replaceable from the external electronic and pneumatic actuators box. Functionality of the LFCS is tested by connecting it to a microfluidic droplet generator, rendering highly stable flow rates and allowing generation of monodisperse droplets over a wide range of flow rates. The results indicate the successful performance of the LFCS with significant improvements over existing LFCS devices, facing the possibility of using the system for biological applications such as generating distinct perfusion modes in cell culture, novel digital microfluidics. Moreover, the integration capabilities and the reproducible fabrication method enable straightforward transition from prototype to product in a way that is lean, cost-effective and with reduced risk.

Design, construction, and optimization of a novel, modular, and scalable incubation chamber for continuous viral inactivation.

We designed, built or 3D printed, and screened tubular reactors that minimize axial dispersion to serve as incubation chambers for continuous virus inactivation of biological products. Empirical residence time distribution data were used to derive each tubular design's volume equivalent to a theoretical plate (VETP) values at a various process flow rates. One design, the Jig in a Box (JIB), yielded the lowest VETP, indicating optimal radial mixing and minimal axial dispersion. A minimum residence time (MRT) approach was employed, where the MRT is the minimum time the product spends in the tubular reactor. This incubation time is typically 60 minutes in a batch process. We provide recommendations for combinations of flow rates and device dimensions for operation of the JIB connected in series that will meet a 60-min MRT. The results show that under a wide range of flow rates and corresponding volumes, it takes 75 ± 3 min for 99% of the product to exit the reactor while meeting the 60-min MRT criterion and fulfilling the constraint of keeping a differential pressure drop under 5 psi. Under these conditions, the VETP increases slightly from 3 to 5 mL though the number of theoretical plates stays constant at about 1326 ± 88. We also demonstrated that the final design volume was only 6% ± 1% larger than the ideal plug flow volume. Using such a device would enable continuous viral inactivation in a truly continuous process or in the effluent of a batch chromatography column. Viral inactivation studies would be required to validate such a design. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:954-965, 2017.

Flow rate-insensitive microparticle separation and filtration using a microchannel with arc-shaped groove arrays

Inertial microfluidics can separate microparticles in a continuous and high-throughput manner, and is very promising for a wide range of industrial, biomedical and clinical applications. However, most of the proposed inertial microfluidic devices only work effectively at a limited and narrow flow rate range because the performance of inertial particle focusing and separation is normally very sensitive to the flow rate (Reynolds number). In this work, an innovative particle separation method is proposed and developed by taking advantage of the secondary flow and particle inertial lift force in a straight channel (AR = 0.2) with arc-shaped groove arrays patterned on the channel top surface. Through the simulation results achieved, it can be found that a secondary flow is induced within the cross section of the microchannel and guides different-size particles to the corresponding equilibrium positions. On the other hand, the effects of the particle size, flow rate and particle concentration on particle focusing and separation quality were experimentally investigated. In the experiments, the performance of particle focusing, however, was found relatively insensitive to the variation of flow rate. According to this, a separation of 4.8 and 13 µm particle suspensions was designed and successfully achieved in the proposed microchannel, and the results show that a qualified particle separation can be achieved at a wide range of flow rate. This flow rate-insensitive microfluidic separation (filtration) method is able to potentially serve as a reliable biosample preparation processing step for downstream bioassays.

Study of dynamical behaviour of the plasma in a dc non-transferred plasma torch using fast imaging

The dynamical behaviour of the plasma in a dc non-transferred plasma torch is the result of complex interactions between various forces acting on the plasma column. We have studied this behaviour in a novel experiment comprising a low power (∼25 kW) torch and fast imaging diagnostics. The nitrogen gas plasma torch was operated at atmospheric pressure for a wide range of gas flow rates (20–60 lpm) and currents (70–120 A). A strong axial external magnetic field (100–500 G) was introduced and end-on images of the plasma column were captured using a high speed camera of frame rate ∼117 000 fps. The studies have yielded dominant role of external magnetic on the arc root dynamics. The column is clearly distinguishable in three main parts: central plasma, cathode-anode junction, and radial component of column that attaches to the anode. The dynamics of the column, especially the angular rotational speed of the radial part of the column, is analyzed in detail in terms of the forces that act upon it. The nature of the arc root attachment is observed to vary with variation in main experimental parameters, such as current, magnetic field, and flow. Arguments are invoked to explain the observed phenomena and a model of the physical processes is presented to explain the phenomena.

Applications of artificial neural network (ANN) method for performance prediction of the effect of a vertical 90° bend on an air–silicone oil flow

Knowledge of how the presence of a bend can change the flow patterns of a gas–liquid mixture is important for the design of multiphase flow systems, particularly to prevent burn-out and erosion–corrosion. Burn-out and erosion–corrosion both have serious implications for heat and mass transfer. The objective of this work therefore is to train an artificial neural network (ANN), a powerful interpolation technique, to predict the effect of a vertical 90o bend on an air–silicone oil mixture over a wide range of flow rates. Experimental data for training, validation, testing and final prediction were obtained using advanced instrumentation, wire mesh sensor (WMS) and high speed camera. The performance of the models were evaluated using the mean square error (MSE), average absolute relative error (MAE), Chi square test (X2) and cross correlation coefficients (R). The performance discriminator X2 for prediction of average void fraction is 2.57e-5 and that for probability density function (PDF) of void fraction MAE is 0.0028 for best performing models. The well trained ANN is then used to predict the effects of the two input parameters individually. The predicted results show that for the before the bend scenario, the most effective input parameter that reflects a change in flow pattern is the gas superficial velocity. On the other hand, the most unfavourable output parameter to measure after the bend is the average void fraction based on the fact that the flow near the bend is a developing one.

Mass transfer performance and correlations for CO2 absorption into aqueous blended of DEEA/MEA in a random packed column

The mass transfer performance of CO2 absorption into blended N,N‐diethylethanolamine (DEEA)/ethanolamine (MEA) solutions was investigated using a lab‐scale absorber (H = 1.28 m, D = 28 mm) packed with Dixon ring random packing. The mass transfer coefficient KGav, the unit volume absorption rate Φ, outlet concentration of CO2 (yCO2), and the bottom temperature Tbot of CO2 in aqueous DEEA/MEA solutions were determined over the feed temperature range of 298.15–323.15 K, lean CO2 loading of 0.15–0.31 mol/mol, over a wide range of liquid flow rate of 3.90–9.75 m3/m2‐h, by using inert gas flow rate of 26.11–39.17 kmol/m2‐h and 6–18 kPa CO2 partial pressure. The results show that liquid feed temperature, lean CO2 loading, liquid flow rate, and CO2 partial pressure had significant effect on those parameters. However, the inert gas flow rate had little effect. To allow the mass transfer data to be really utilized, KGav and yout correlations for the prediction of mass transfer performance were proposed and discussed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3048–3057, 2017

Scrutinization of Flow in the Immediate Vicinity of a Brink in a Tilting Flume

The flow characteristics of the subcritical and supercritical flows over an unconfined free overfall in a rectangular channel are presented with experimental data available in the literature. The experimental observations cover a wide range of flow rate on mild, steep and adverse slopes. The dependence of the ratio of the brink depth to the critical depth according to several flow parameters is examined. The relation between the flow rate and the brink depth ratio is both explicitly and implicitly demonstrated. The location of the critical depth for subcritical flows upstream of the brink is also investigated. It is concluded that the location of the critical depth for subcritical flows depends on the Froude number, the channel bed slope and the Manning roughness coefficient. Furthermore, it is observed that there is a significant similarity of the water surface profiles in the immediate upstream vicinity of the brink of the subcritical and supercritical flows.

Focusing and alignment of erythrocytes in a viscoelastic medium

Viscoelastic fluid flow-induced cross-streamline migration has recently received considerable attention because this process provides simple focusing and alignment over a wide range of flow rates. The lateral migration of particles depends on the channel geometry and physicochemical properties of particles. In this study, digital in-line holographic microscopy (DIHM) is employed to investigate the lateral migration of human erythrocytes induced by viscoelastic fluid flow in a rectangular microchannel. DIHM provides 3D spatial distributions of particles and information on particle orientation in the microchannel. The elastic forces generated in the pressure-driven flows of a viscoelastic fluid push suspended particles away from the walls and enforce erythrocytes to have a fixed orientation. Blood cell deformability influences the lateral focusing and fixed orientation in the microchannel. Different from rigid spheres and hardened erythrocytes, deformable normal erythrocytes disperse from the channel center plane, as the flow rate increases. Furthermore, normal erythrocytes have a higher angle of inclination than hardened erythrocytes in the region near the side-walls of the channel. These results may guide the label-free diagnosis of hematological diseases caused by abnormal erythrocyte deformability.

Microfabricated Electrospray Thruster Array with High Hydraulic Resistance Channels

Electrospray thrusters can deliver the efficient primary propulsion and attitude control actuation needed by small satellites. The microfabricated multiemitter array is an ideal implementation of this technology because it addresses the thrust, volume, mass, and scalability requirements across the size range of small satellites. This paper describes the microfabrication and testing of an internally fed 64-emitter array. The main goal is to decouple the design and fabrication of the emitters from the need to provide a flowpath with sufficient hydraulic resistance for each emitter. The latter has traditionally been achieved by reducing the diameter of the emitter’s inner channel or by filling it with a bed of beads; whereas in this paper, individual flow-restrictive channels are etched on the back of the emitter wafer, connecting each emitter to a common distribution manifold. The source operates steadily in vacuum. Beam interception by the extractor is negligible in a wide range of flow rates and emitter potentials. The thrust, mass flow rate, specific impulse, and propulsive efficiency are calculated using the time-of-flight technique. These parameters range between 8.1 and , and , 96 and 236 s, and 61 and 75% using the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as propellant.