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  • 1
    Electronic Resource
    Electronic Resource
    Liquid backmixing in bubble columns via computer-automated radioactive particle tracking (CARPT) (1993)
    Springer
    Experiments in fluids 16 (1993), S. 1-9 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A single, fully wettable, neutrally buoyant, small radioactive particle and 16 scintillation detectors are utilized to monitor particle motion in gas-liquid bubble columns of different heights and diameters and at different gas superficial velocities. Instantaneous velocities, time-averaged velocities, Reynolds stresses and eddy diffusivities are computed from the particle position versus time data. Anisotropy, indicated by the data, was confirmed by Hurst's rescaled R/S analysis of the fluctuating velocities. For the radial direction, Hurst's exponent is about 0.5 in agreement with a random walk (diffusion)-type mechanism, while in the axial direction, Hurst's exponent of about 0.7 indicates the persistence of long-range effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188499
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of goethite (.alpha.-FeOOH) through the oxidation of a ferrous hydroxide slurry (1992)
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 31 (1992), S. 2516-2524 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie00011a016
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental and modeling studies in fixed-bed char gasification (1986)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 25 (1986), S. 988-996 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/i200035a025
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  • 4
    Electronic Resource
    Electronic Resource
    Reactions of particles with nonuniform distribution of solid reactant. The shrinking core model (1984)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 23 (1984), S. 330-334 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/i200025a024
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  • 5
    Electronic Resource
    Electronic Resource
    Radioactive particle tracking technique for investigation of phase recirculation and turbulence in multiphase systems (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4361-4372 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The development of a noninvasive PC-based computer automated radioactive particle tracking (CARPT) facility for investigation of phase recirculation and turbulence in multiphase systems such as fluidized beds and bubble columns is presented. In this facility, the motion of a single radioactive particle, which is dynamically similar to the recirculating phase, is monitored by an array of scintillation detectors which surround the test section. An on-line computer is used to map the flow field of the recirculating phase. The data acquisition is achieved by commercially available nuclear instrumentation via a modular, high-speed GPIB-CAMAC system through assembly language software. Using CARPT, solids' motion in gas-fluidized beds and liquid motion in bubble columns have been investigated. The capabilities and versatility of the CARPT facility is described by illustrating some typical results for mean recirculation in gas-fluidized beds with and without internals and in a gas-liquid bubble column. The results include the mean circulation profiles and turbulence parameters such as the Reynolds normal and shear stresses and the turbulent eddy dispersion coefficients. Potential applications of CARPT technique to other recirculating systems are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143736
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  • 6
    Electronic Resource
    Electronic Resource
    Mathematical model for predicting the molecular intensity of a solenoid-actuated pulsed beam source (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 3492-3498 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A mathematical model for evaluating the molecular intensity produced by a solenoid-actuated pulsed beam source is described. The particular source studied here is used to introduce reactant gas pulses at various user-specified intervals into a fixed-bed microreactor system for transient catalysis studies where quantification of the inlet pulse intensity is required for data analysis. The model equations which describe the beam source performance utilize relationships from one-dimensional isentropic gas expansion, gas effusion through a small hole, and macroscopic mass balances around the valve orifice from which a closed-form algebraic expression for the pulse intensity is obtained. The parameters in this expression represent observables which include the ideal gas specific heat capacity ratio, the stagnation properties of the gas in the supply chamber of the beam source, and the beam valve driver settings. Comparisons between experimental and predicted values for the pulse intensities, where the latter are of the order 1017 molecules per pulse, show excellent agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144273
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  • 7
    Electronic Resource
    Electronic Resource
    Self-inhibited rate in gas-solid noncatalytic reactions: the "rotten apple" phenomenon and multiple reaction pathways (1983)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 22 (1983), S. 55-61 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/i100009a010
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  • 8
    Electronic Resource
    Electronic Resource
    Laminar radial flow electrochemical reactors. I. Flow fields (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 768-780 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The velocity fields of three laminar radial flow electrochemical reactors are modeled using numerical and semi-analytical techniques. The capillary gap cell configuration is modeled using Galerkin finite element (GFEM) analysis and the asymptotic form of its velocities presented. An approximate asymptotic expression for entry length is also derived and compared to predicted entry lengths from the GFEM. Qualitative agreement is achieved. Two areas of flow separation are observed, their location being a function of gap width, flow Reynolds number (Re) and inlet pipe diameter. The rotating electrolyzer (REL) flow field is also simulated with the GFEM model. The insensitivity of the REL radial velocity profiles as a function of flow rate is shown. The shape of the radial velocity profiles and the degree of separation of the radial velocity jets are shown to be determined by the Taylor number (being the ratio of half-gap width over the theoretical boundary layer thickness). The asymptotic entry length solution is shown to provide a better estimate for this cell than for the capillary gap cell. Unlike the previous cells the pump cell shows less asymptotic behavior and is therefore more difficult to simulate. The GFEM approach is usually too costly for this cell and therefore perturbation techniques are applied. The resulting semi-analytical solution adequately represents laminar pump cell velocity profiles over a broad range of parameter values and is very short and easy to implement. One high Taylor number simulation is performed using the GFEM and the previously reported decoupling of electrodic mass transfer is interpreted via velocity profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01016906
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  • 9
    Electronic Resource
    Electronic Resource
    Laminar radial flow electrochemical reactors. III. Electroorganic sysnthesis (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 856-867 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper investigates the performance and design of three laminar radial flow electrochemical cells (the capillary gap cell, stationary discs; the rotating electrolyzer, co-rotational discs; the pump cell, one disc rotating and the other stationary). Modeling of a competing electrosynthesis pathway is described — the methoxylation of furan. The model developed incorporates convective, diffusive and migrative influences with three homogeneous and two electrodic reactions. Two sizes of reactors are considered and the performance of the different reactor types analyzed as a function of size. The superiority of the rotational cells is illustrated for this reaction scheme compared to both the capillary gap cell (CG) and a parallel plate reactor (PPER). Scale-up criteria are scrutinized and two approaches to laminar radial flow reactor scale-up are investigated. The one suggested herein shows that Taylor number, residence time,IR drop and rotational Reynolds number must all be accounted for even with a fairly simple electrosynthesis pathway. A quantitative evaluation of this scale-up procedure is included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007933
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  • 10
    Electronic Resource
    Electronic Resource
    Laminar radial flow electrochemical reactors. II. Convective diffusion of inert tracer (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 845-855 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mixing is investigated in three laminar radial flow cells (capillary gap cell (stationary discs), pump cell (one disc spinning) and the rotating electrolyser (co-rotating discs)) using numerical and semianalytical methods for inert tracer transport. Results are compared to existing data. Mixing in the three cells is modelled using finite element techniques applied to convection-dominated inert tracer transport. For the capillary gap cell modes of tracer tagging and detection are commented on with respect to which type provides the correct representation of the residence time distribution. The extent of cross-gap communication, from anode to cathode, is quantified and compared to that observed in the other radial cell designs. Two semi-analytical solutions (convection only, Taylor diffusion) are derived for inert tracer transport in this configuration and are compared to the detailed numerical results. Convection only is relevant fort d/t c ratios of greater than 100 and the Taylor diffusion model applies fort d/t c ratios of about 0.10 and only beyond a critical radius defined herein. Pump cell (PC) mixing is modelled using finite element techniques for the tracer, the velocity field being provided by a semi-analytical solution. Mixing is quantified in this cell and cross-gap communication evaluated. The large axial velocities provide for significant cross-gap mixing. The rotating electrolyser is modelled and the efficiency of separation of catholyte/anolyte streams is observed to be determined by Taylor number (Taylor number (α) — ratio of half-gap width divided by theoretical boundary layer thickness). The superiority of separation in this cell is quantified by definition of the zeroth wall moment and comparison with the other two radial cells. For the example modelled, cross-gap communication was less than half that of the other cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007932
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