Flow structure of the dispersed gasphase in real multiphase chemical reactors investigated by a new ultrasound–doppler technique

Bröring, S.; Fischer, J.; Korte, Thomas; Sollinger, S.; Lübbert, Α.

doi:10.1002/cjce.5450690604

Cited by 47 publications

(27 citation statements)

References 6 publications

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“…Generally, the ultrasonic pulse is emitted into the medium along the measuring line by a piezoelectric transducer ultrasonically coupled to the outside of the vessel [20,26]. This transducer receives the echo reflected from the surface of microparticles suspended in the medium.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Ihejirika

Ein‐Mozaffari

2007

Chem Eng & Technol

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A commercial CFD package was used to simulate the 3D flow field generated in a cylindrical tank by a helical ribbon impeller. The study was carried out using a pseudoplastic fluid with yield stress in the laminar mixing region. Ultrasonic Doppler velocimetry (UDV), a noninvasive fluid flow measurement technique for opaque systems, was used to measure xanthan gum velocity. From flow field calculations and tracer homogenization simulations, power consumption and mixing time results were obtained. The torque and power characteristics remain the same for upward and downward pumping of the impeller, but the mixing times are considerably longer for the downward pumping mode. Overall, the numerical results showed good agreement with experimental results and correlations developed by other researchers. From the power and mixing time results, two efficiency criteria were utilized to determine the best pumping mode of the impeller.

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Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Ihejirika

Ein‐Mozaffari

2007

Chem Eng & Technol

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“…These acoustic signals undergo significant attenuation due to reflection on gas bubbles and thus are unsuitable for use under high void fractions. 34 A combination of imaging system with fiber optic probe and endoscopic probe has been used by some authors in liquid-solid or gas-solid systems. 35,36 Dual-probe hot-film anemometry has been used by Wang & Ching 37 to measure bubble velocities in the gas-liquid flow at low solids concentration conditions.…”

Section: Intrusive Techniquesmentioning

confidence: 99%

Untitled

2017

IPCSE

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Abbreviations BSD, bubble size distribution; PET, positron emission tomography; PIV, particle image velocimetry, RPT; radioactive particle tracking; NMR, nuclear magnetic resonance imaging IntroductionMultiphase flow systems have been applied extensively in chemical, physical, petrochemical and biochemical processing industries.1-3 Among different multiphase flow systems, bubbly flow is a two phase flow where small bubbles are dispersed or suspended in a liquid continuum. Typical features of this flow are moving and deformable interfaces of bubbles in time and space domains and complex interactions between the interfaces, and also between the bubbles and the liquid flow. Bubbly flows occur frequently in natural systems and are also used for different applications in energy-producing and chemical and petroleum industries. Some of the common applications involve bubble columns which are used as reactors in a variety of chemical and biochemical processes, e.g. the Fischer-Tropsch process for hydrocarbon synthesis, hydrogenation of unsaturated oil, coal liquefaction, fermentation, waste water treatment etc. 4,5 Bubbly flows are also ubiquitously found in flotation cells 6 and spargers 7 and have recently been investigated extensively for aeration studies. [8][9][10][11][12] Concentration, size and velocity distributions of solid or liquid particles suspended in gas or liquid are important in many processes such as meteorological research, biology, environmental protection, chemistry, medicine and agricultural engineering. Further, commercial activities such as conversion of natural gas to fuels and chemicals have prompted further fundamental research in fluid and bubble dynamics, transport phenomena and the effects due to scale up of three-phase fluidization systems.The prediction of pressure drop and wall heat transfer is necessary in many of these processes and these are strongly dependent upon the concentration, morphology and spatial distribution of the bubbles. 13 Similarly, in many liquid-gas systems, gases are dispersed in liquids to obtain large interfacial area for chemical reactions, heat and mass transfer processes. The rate of these processes is determined by bubble surface area flux which is closely linked to the bubble size distribution. 14 DiscussionDifferent techniques have been employed to measure bubble size distributions. Broadly, it can be divided into two categoriesintrusive and non-intrusive techniques.15 Both these methods have been extensively reported in the literature and a brief description of different intrusive and non-intrusive techniques is provided below, Intrusive techniquesConsiderable intrusive techniques have been developed to study bubble behavior in gas-liquid and gas-liquid-solid fluidized systems. These intrusive techniques include impedance (conductivity or resistivity) probes, capillary suction probes, 16 optical fiber probes, ultrasound probes, endoscopic probes, wire-mesh sensors 17 and hot film anemometry.The impedance probe has been applied to measure the bubble volume f...

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“…In this paper, we present detailed data obtained by two new ultrasound pulse response techniques. The ultrasound pulse Doppler technique, discussed by Broring et al [ 6 ] , can provide well resolved bubble velocity data from flows in chemical and biochemical reactors and even data measured during production runs. The ultrasound pulse amplitude analysis technique was applied to measurement of scalar bubble properties.…”

Section: Introductionmentioning

confidence: 99%

Gas‐phase properties in stirred tank bioreactors

1992

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Bubble properties in stirred tank bioreactors equipped with standard radial flow Rushton turbines have been investigated. Bubble velocity patterns within a stirred tank reactor were derived from measured local bubble velocity distributions. Local information on specific interfacial areas, bubble number densities and bubble diameters together with local gas hold-ups, measured in a model medium at gas flow rates which are employed in practice, is presented. All measurements were performed with two new ultrasound pulse techniques which can be used in model media as well as during real cultivation processes.

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Flow structure of the dispersed gasphase in real multiphase chemical reactors investigated by a new ultrasound–doppler technique

Cited by 47 publications

References 6 publications

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

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Gas‐phase properties in stirred tank bioreactors

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