Showing papers on "Volumetric flow rate published in 2017"

Heat Transfer Analysis Of Nano-fluid Flow In A Converging Nozzle With Different Aspect Ratios

Abstract: The study evaluates the nanofluid using finite element analysis with base fluid (water) and seeding particles (Aluminum oxide). This is placed over a convergence channel consisting of varying aspect ratio that are evaluated quantitatively to enhance the heat transfer properties of the nanofluid.We have considered frictional loss characteristics that increases the flow of the fluid with Reynolds numbers varying from 100-2000 is compared.A baseline modeling is established using the methodology analysis for the fluid flow over a rectangular chamber that is designed in the form of a square duct of ratio 1:1. The analysis is carried out over the heat transfer and flow rate characteristics of the nanofluid that converges into the square ducts with different aspect ratio, is analyzed.The concentration of the nano fluid is maintained at the constant rate, which is used for studying the flow rate influence over different aspect ratios. The thermal and flow characteristics is analyzed in such situation and validated against other literatures to check the efficiency in the converging rectangular oxygen free copper channel.The simulation results shows an increase in temperature on the duct out and drop in temperature on the inlet walls of the tube.The pressure changes and shear stress along the walls of the chamber is not much noticed and it is constant throughout the entire chamber.

Observation and Analysis of Water Transport through Graphene Oxide Interlamination

Abstract: Water transport inside graphene-based materials has drawn much attention nowadays because of its promising potential in ions filtration applications. Using molecular dynamics (MD) simulations, we investigated the mechanism of water transport inside the interlayer gallery between graphene oxide layers. The model of slipped-Poiseuille flow was cited to depict the characteristic transport of interlayer flow. This significant flow rate was related to slip velocity of water, which is constrained by hydrogen interactions between water molecules and hydroxyl groups. We find that hydrogen-bond networks are correlated with both functionalization and nanoconfinement. MD simulation results show that the slip velocity is negatively correlated with oxide concentration while independent of the array of hydroxyl groups, and the volumetric flux is linearly dependent to the slip velocity. It reveals that graphene oxide layers could get better water permeability after reduction.

X-ray Microtomography of Intermittency in Multiphase Flow at Steady State Using a Differential Imaging Method.

Abstract: We imaged the steady state flow of brine and decane in Bentheimer sandstone. We devised an experimental method based on differential imaging to examine how flow rate impacts impact the pore-scale distribution of fluids during coinjection. This allows us to elucidate flow regimes (connected, or breakup of the nonwetting phase pathways) for a range of fractional flows at two capillary numbers, Ca, namely 3.0 × 10-7 and 7.5 × 10-6. At the lower Ca, for a fixed fractional flow, the two phases appear to flow in connected unchanging subnetworks of the pore space, consistent with conventional theory. At the higher Ca, we observed that a significant fraction of the pore space contained sometimes oil and sometimes brine during the 1 h scan: this intermittent occupancy, which was interpreted as regions of the pore space that contained both fluid phases for some time, is necessary to explain the flow and dynamic connectivity of the oil phase; pathways of always oil-filled portions of the void space did not span the core. This phase was segmented from the differential image between the 30 wt % KI brine image and the scans taken at each fractional flow. Using the grey scale histogram distribution of the raw images, the oil proportion in the intermittent phase was calculated. The pressure drops at each fractional flow at low and high flow rates were measured by high-precision differential pressure sensors. The relative permeabilities and fractional flow obtained by our experiment at the mm-scale compare well with data from the literature on cm-scale samples.

CO2-CH4 conversion and syngas formation at atmospheric pressure using a multi-electrode dielectric barrier discharge

Abstract: The conversion of CO2 and CH4 into value-added chemicals is studied in a new geometry of a dielectric barrier discharge (DBD) with multi-electrodes, dedicated to the treatment of high gas flow rates. Gas chromatography is used to define the CO2 and CH4 conversion as well as the yields of the products of decomposition (CO, O2 and H2) and of recombination (C2H4, C2H6 and CH2O). The influence of three parameters is investigated on the conversion: the CO2 and CH4 flow rates, the plasma power and the nature of the carrier gas (argon or helium). The energy efficiency of the CO2 conversion is estimated and compared with those of similar atmospheric plasma sources. Our DBD reactor shows a good compromise between a good energy efficiency and the treatment of a large CO2 flow rate.

Mixing and mass transfer in a pilot scale U-loop bioreactor

Abstract: A system capable of handling a large volumetric gas fraction while providing a high gas to liquid mass transfer is a necessity if the metanotrophic bacterium Methylococcus capsulatus is to be used in single cell protein (SCP) production. In this study, mixing time and mass transfer coefficients were determined in a 0.15 m3 forced flow U-loop fermenter of a novel construction. The effect on the impeller drawn power when a gas was introduced into the system was also studied. Mixing time decreased and mass transfer increased with increasing volumetric liquid flow rate and specific power input. This happened also for a large volume fraction of the gas, which was shown to have only minor effect on the power drawn from the pump impeller. Very large mass transfer coefficients, considerably higher than those obtainable in an STR and previous tubular loop reactors, could be achieved in the U-loop fermenter equipped with static mixers at modest volumetric liquid and gas flow rates. Biotechnol. Bioeng. 2017;114: 344-354. © 2016 Wiley Periodicals, Inc.

Shear Rate Determination from Pore-Scale Flow Fields

Abstract: Aqueous solutions with polymer additives often used to improve the macroscopic sweep efficiency in oil recovery typically exhibit non-Newtonian rheology. In order to predict the Darcy-scale effective viscosity $$\mu _{\mathrm{eff}} $$ required for practical applications often, semi-empirical correlations such as the Cannella or Blake–Kozeny correlation are employed. These correlations employ an empirical constant (“C-factor”) that varies over three orders of magnitude with explicit dependency on porosity, permeability, fluid rheology and other parameters. The exact reasons for this dependency are not very well understood. The semi-empirical correlations are derived under the assumption that the porous media can be approximated by a capillary bundle for which exact analytical solutions exist. The effective viscosity $$\mu _{\mathrm{eff}} (v_{\mathrm{Darcy}} )$$ as a function of flow velocity is then approximated by a cross-sectional average of the local flow field resulting in a linear relationship between shear rate $$\gamma $$ and flow velocity. Only with such a linear relationship, the effective viscosity can be expressed as a function of an average flow rate instead of an average shear rate. The local flow field, however, does in general not exhibit such a linear relationship. Particularly for capillary tubes, the velocity is maximum at the center, while the shear rate is maximum at the tube wall indicating that shear rate and flow velocity are rather anti-correlated. The local flow field for a sphere pack is somewhat more compatible with a linear relationship. However, as hydrodynamic flow simulations (using Newtonian fluids for simplicity) performed directly on pore-scale resolved digital images suggest, flow fields for sandstone rock fall between the two limiting cases of capillary tubes and sphere packs and do in general not exhibit a linear relationship between shear rate and flow velocity. This indicates that some of the shortcomings of the semi-empirical correlations originate from the approximation of the shear rate by a linear relationship with the flow velocity which is not very well compatible with flow fields from direct hydrodynamic calculations. The study also indicates that flow fields in 3D rock are not very well represented by capillary tubes.

Liquid–Liquid Two-Phase Flow Patterns in Y-Junction Microchannels

Abstract: Experiments are carried out to study liquid–liquid two-phase flow patterns in Y-junction microchannels etched in glass chips. The liquid–liquid test systems used in the experiments are the three standard test systems recommended by the European Federation of Chemical Engineering (EFCE) for extraction studies. Four different flow patterns—slug flow, slug and droplet flow, droplet flow, and parallel flow—are observed. Effects of microchannel diameter, flow rate, interfacial tension of the liquids, and hydrophobicity of channel wall on two-phase flow patterns have been studied, and flow regime maps are presented and discussed.

Continuous Ethanol Production from Synthesis Gas by Clostridium ragsdalei in a Trickle-Bed Reactor

Abstract: A trickle-bed reactor (TBR) when operated in a trickle flow regime reduces liquid resistance to mass transfer because a very thin liquid film is in contact with the gas phase and results in improved gas–liquid mass transfer compared to continuous stirred tank reactors (CSTRs) In the present study, continuous syngas fermentation was performed in a 1-L TBR for ethanol production by Clostridium ragsdalei The effects of dilution and gas flow rates on product formation, productivity, gas uptakes and conversion efficiencies were examined Results showed that CO and H2 conversion efficiencies reached over 90% when the gas flow rate was maintained between 15 and 28 standard cubic centimeters per minute (sccm) at a dilution rate of 0009 h−1 A 4:1 molar ratio of ethanol to acetic acid was achieved in co-current continuous mode with both gas and liquid entered the TBR at the top and exited from the bottom at dilution rates of 0009 and 0012 h−1, and gas flow rates from 101 to 122 sccm and 159 to 189 sccm, respectively

Analysis of micromixing of non-Newtonian fluids driven by alternating current electrothermal flow

Abstract: Biochemical applications pertaining to chip scale mixing often deal with fluids which exhibit non-Newtonian behavior. This paper presents numerical investigations on the characterization of the effect of shear dependent apparent viscosity of non-Newtonian fluids on the mixing efficiency and volume flow rate in an alternating current electrothermal micromixer driven by electrothermal micropump. The micromixer consists of thin film asymmetric pairs of electrodes on a microgrooved channel floor and an array of electrode pairs on the top wall. The results show that mixing quality and flow rate have a strong dependence on shear dependent viscosity of the non-Newtonian fluid. Using a power law based constitutive model, it is found that for specific design parameters, more uniform and homogeneous mixing is achieved with increasing flow behavior index. Thus, electrothermal mixing in a microfluidic device has higher efficiency and effectiveness in the regime of dilatant fluids compared to Newtonian and pseudoplastic fluids. Our results also demonstrate that an optimal voltage for maximum mixing efficiency progressively reduces, while the flow rate continues to increase monotonically, with enhancements in the applied AC potential. These results hold practical implications in several emerging applications, including chemical analysis of biological fluids in general, and biomedical diagnostics in particular.

Electro-kinetically driven peristaltic transport of viscoelastic physiological fluids through a finite length capillary: Mathematical modeling

Abstract: Analytical solutions are developed for the electro-kinetic flow of a viscoelastic biological liquid in a finite length cylindrical capillary geometry under peristaltic waves. The Jefferys' non-Newtonian constitutive model is employed to characterize rheological properties of the fluid. The unsteady conservation equations for mass and momentum with electro-kinetic and Darcian porous medium drag force terms are reduced to a system of steady linearized conservation equations in an axisymmetric coordinate system. The long wavelength, creeping (low Reynolds number) and Debye-Huckel linearization approximations are utilized. The resulting boundary value problem is shown to be controlled by a number of parameters including the electro-osmotic parameter, Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity), and Jefferys' first parameter (ratio of relaxation and retardation time), wave amplitude. The influence of these parameters and also time on axial velocity, pressure difference, maximum volumetric flow rate and streamline distributions (for elucidating trapping phenomena) is visualized graphically and interpreted in detail. Pressure difference magnitudes are enhanced consistently with both increasing electro-osmotic parameter and Helmholtz-Smoluchowski velocity, whereas they are only elevated with increasing Jefferys' first parameter for positive volumetric flow rates. Maximum time averaged flow rate is enhanced with increasing electro-osmotic parameter, Helmholtz-Smoluchowski velocity and Jefferys' first parameter. Axial flow is accelerated in the core (plug) region of the conduit with greater values of electro-osmotic parameter and Helmholtz-Smoluchowski velocity whereas it is significantly decelerated with increasing Jefferys' first parameter. The simulations find applications in electro-osmotic (EO) transport processes in capillary physiology and also bio-inspired EO pump devices in chemical and aerospace engineering.