The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
P. Stonestreet - One of the best experts on this subject based on the ideXlab platform.
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operation and optimization of an Oscillatory Flow continuous reactor
Industrial & Engineering Chemistry Research, 2001Co-Authors: Adam Harvey, M R Mackley, P. StonestreetAbstract:Oscillatory Flow reactors (OFRs) are a novel type of continuous reactor, in which tubes fitted with orifice plate baffles have an Oscillatory motion superimposed upon the net Flow of the process fluid. The combination of baffles and the Oscillatory motion creates a Flow pattern conducive to efficient heat and mass transfer while maintaining plug Flow. Unlike conventional tubular reactors, where a minimum Reynolds number must be maintained, tube-side mixing is independent of the net Flow, allowing long residence times to be achieved in a reactor of greatly reduced length-to-diameter ratio. We have evaluated a pilot-scale OFR as a method for continuous production of sterols in an ester saponification reaction. The OFR achieved the required product specification, in a residence time one-eighth that of a full-scale batch reactor. To better understand the effect of the process variables on the reactor performance, the OFR was modeled using a tanks-in-series residence time distribution, combined with the saponi...
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Protein refolding in an Oscillatory Flow reactor
Biotechnology Letters, 2001Co-Authors: Malcolm R. Mackley, P. Stonestreet, Anton P. J. MiddelbergAbstract:We demonstrate that an Oscillatory Flow reactor is a viable reactor for protein refolding via direct dilution. The mixing characteristics of the Oscillatory Flow reactor are well described and controllable and, importantly, can be scaled-up to process scale without a loss of mixing efficiency. This makes the Oscillatory Flow reactor an attractive alternative to conventional stirred-tank reactors for process-scale renaturation.
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the effects of Oscillatory Flow and bulk Flow components on residence time distribution in baffled tube reactors
Chemical Engineering Research & Design, 1999Co-Authors: P. Stonestreet, P M J Van Der VeekenAbstract:A characteristic of Oscillatory Flow mixing in a baffled tube is that the residence time distribution performance can be affected independently of net Flow conditions. The effects of both the Oscillatory velocity and the throughput velocity on the residence time distribution performance has been investigated in a 24 mm diameter, 2.8 m long, baffled tube Oscillatory Flow reactor. The experiments were performed by applying the tanks-in-series model to ’perfect pulse’ tracer experiments over a wide range of Oscillatory conditions and Flow rates. An optimum set of Oscillatory and net Flow conditions was found which resulted in near plug Flow behaviour, usually 50 tanks-in-series (N) or greater. For a throughput velocity, N was found to be sensitive to both the amplitude and frequency of oscillation, and this dependence could be expressed by means of the Oscillatory Flow Reynolds number (Re0), which combines both parameters. A unique value for Re0 for each value of the net Flow Reynolds number (Ren) gave the closest approach to a plug Flow RTD. To relate the Oscillatory and net Flows, a dimensionless velocity ratio, ψ, was used, defined as Reo/Ren. In order to relate the RTD performance for different Flow rates, the tanks-in-series model was non-dimensionalized by the use of a stage-wise efficiency term,η, defined as the ratio of N to the theoretical number of stages. Over the range of Oscillatory and net Flow conditions studied, it was found that the range 2 ≤ψ ≤ 4 corresponded to the optimum RTD conditions, where efficiencies close to 1 were achieved. It was concluded that these dimensionless parameters were sufficient to select, a priori, the Oscillatory parameters necessary to obtain the optimum RTD in an Oscillatory Flow reactor based on a desired throughput specification.
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Residence time distribution enhancement in reactors using Oscillatory Flow
Chemical Engineering Research & Design, 1996Co-Authors: Malcolm R. Mackley, P. Stonestreet, Edward P.l. Roberts, Xiongwei NiAbstract:The published and ongoing research concerning Oscillatory Flow in baffled tubes is reviewed. A number of key features are identified. Using this technology it is possible to achieve a near plug Flow behaviour and a long residence time with a relatively short tubular reactor. Oscillatory Flow in baffled tubes has been shown to enhance process engineering properties such as mixing, heat transfer and gas-liquid mass transfer. The technology is well suited to multi-phase system. Furthermore, it is possible to control the performance of the device independently from the throughput using the amplitude and frequency of oscillation. A number of potential applications are identified for evaluation.
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heat transfer and associated energy dissipation for Oscillatory Flow in baffled tubes
Chemical Engineering Science, 1995Co-Authors: M R Mackley, P. StonestreetAbstract:We report experimental data on the heat transfer performance of a periodically baffled tube subject to both steady (net) Flow and Oscillatory Flow. The data show that, in particular, at a low net Flow Reynolds number, significant heat transfer enhancement can be achieved with the superposition of fluid oscillations. A general correlation is derived for the measured Nusselt number as a function of both net Flow and Oscillatory Reynolds number. Dynamic pressure drop data for Oscillatory Flow are also reported, and estimates of energy efficiency for obtaining heat transfer enhancement made from these measurements are compared with smooth wall turbulent Flow equations. For large amplitudes of oscillation (equivalent to half the tube diameter) the overall power dissipation follows the quasi-steady theory. At smaller amplitudes of oscillation the power dissipation was larger than predicted by the quasi-steady theory, indicating an increased eddy interaction.
M R Mackley - One of the best experts on this subject based on the ideXlab platform.
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residence times and mixing of a novel continuous Oscillatory Flow screening reactor
Chemical Engineering Science, 2004Co-Authors: Nuno M Reis, A A Vicente, J A Teixeira, M R MackleyAbstract:This paper is concernedwith the fluidmechanics andmixing performance of a novel Oscillatory Flow screening reactor. Using fibre optic probes, a mixing coefficient km is d eterminedfor the system as a function of the appliedfluidoscillation frequency andamplitud e. In a continuous operation mean residence time and a backmixing coefficient g are estimatedas a function of the oscillation cond itions. Finally, in order to compare data with numerical simulations steady state Flow data are also included. The screening reactor presented an intermediate mixing behaviour throughout all the studied range of oscillation amplitudes (0–3 mm centre-to-peak) andfrequencies (0–20 Hz). The backmixing was foundto be highly d epend ent of the oscillation frequency andamplitud e. Nevertheless, a stronger effect of the oscillation amplitude over the axial dispersion was detected presumably due to the increase of the mixing length. On the other hand, the increase of the oscillation frequency was concluded to have the increase in the radial mixing rates as the main effect. Thus, it was possible to achieve a decrease in the axial dispersion with the screening reactor using Oscillatory Flow, when compared to the laminar steady Flow in a plain tube with the same mean internal diameter. 2004 Elsevier Ltd. All rights reserved.
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operation and optimization of an Oscillatory Flow continuous reactor
Industrial & Engineering Chemistry Research, 2001Co-Authors: Adam Harvey, M R Mackley, P. StonestreetAbstract:Oscillatory Flow reactors (OFRs) are a novel type of continuous reactor, in which tubes fitted with orifice plate baffles have an Oscillatory motion superimposed upon the net Flow of the process fluid. The combination of baffles and the Oscillatory motion creates a Flow pattern conducive to efficient heat and mass transfer while maintaining plug Flow. Unlike conventional tubular reactors, where a minimum Reynolds number must be maintained, tube-side mixing is independent of the net Flow, allowing long residence times to be achieved in a reactor of greatly reduced length-to-diameter ratio. We have evaluated a pilot-scale OFR as a method for continuous production of sterols in an ester saponification reaction. The OFR achieved the required product specification, in a residence time one-eighth that of a full-scale batch reactor. To better understand the effect of the process variables on the reactor performance, the OFR was modeled using a tanks-in-series residence time distribution, combined with the saponi...
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heat transfer and associated energy dissipation for Oscillatory Flow in baffled tubes
Chemical Engineering Science, 1995Co-Authors: M R Mackley, P. StonestreetAbstract:We report experimental data on the heat transfer performance of a periodically baffled tube subject to both steady (net) Flow and Oscillatory Flow. The data show that, in particular, at a low net Flow Reynolds number, significant heat transfer enhancement can be achieved with the superposition of fluid oscillations. A general correlation is derived for the measured Nusselt number as a function of both net Flow and Oscillatory Reynolds number. Dynamic pressure drop data for Oscillatory Flow are also reported, and estimates of energy efficiency for obtaining heat transfer enhancement made from these measurements are compared with smooth wall turbulent Flow equations. For large amplitudes of oscillation (equivalent to half the tube diameter) the overall power dissipation follows the quasi-steady theory. At smaller amplitudes of oscillation the power dissipation was larger than predicted by the quasi-steady theory, indicating an increased eddy interaction.
Stephen G Monismith - One of the best experts on this subject based on the ideXlab platform.
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Oscillatory Flow through submerged canopies 1 velocity structure
Journal of Geophysical Research, 2005Co-Authors: Ryan J Lowe, Jeffrey R Koseff, Stephen G MonismithAbstract:[1] Many benthic organisms form very rough surfaces on the seafloor that can be described as submerged canopies. Recent evidence has shown that, compared with a unidirectional current, an Oscillatory Flow driven by surface waves can significantly enhance biological processes such as nutrient uptake. However, to date, the physical mechanisms responsible for this enhancement have not been established. This paper presents a theoretical model to estimate Flow inside a submerged canopy driven by Oscillatory Flow. To reduce the complexity of natural canopies, an idealized canopy consisting of an array of vertical cylinders is used. The attenuation of the in-canopy Oscillatory Flow is shown to be governed by three dimensionless parameters defined on the basis of canopy geometry and Flow parameters. The model predicts that an Oscillatory Flow will always generate a higher in-canopy Flow when compared to a unidirectional current of the same magnitude, and specifically that the attenuation will monotonically increase as the wave orbital excursion length is increased. A series of laboratory experiments are conducted for a range of different unidirectional and Oscillatory Flow conditions, and the results confirm that Oscillatory Flow increases water motion inside a canopy. It is hypothesized that this higher in-canopy Flow will enhance rates of mass transfer from the canopy elements, a problem formally investigated in a companion paper (Lowe et al., 2005b).
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Oscillatory Flow through submerged canopies: 2. Canopy mass transfer
Journal of Geophysical Research, 2005Co-Authors: Ryan J Lowe, Jeffrey R Koseff, Stephen G Monismith, James L. FalterAbstract:[1] Mass transfer rates from submerged canopies constructed from arrays of vertical cylinders were investigated for a range of different cylinder spacings under both unidirectional and Oscillatory Flow. Individual canopy elements made from gypsum were dissolved in fresh water to simulate the mass transfer of dissolved metabolites to and from canopies of living benthic organisms. Mass transfer rates under Oscillatory Flow were up to three times higher than values measured for a comparable unidirectional current. This enhancement was shown to be a strong function of the canopy element spacing. A model was developed to predict canopy mass transfer rates on the basis of the in-canopy Flow speed and was generalized to incorporate either unidirectional or Oscillatory Flow. Agreement between the modeled and experimentally measured mass transfer rates indicate that enhanced mass transfer to/from living benthic canopies under Oscillatory Flow is driven primarily by the higher in-canopy water motion generated by the Oscillatory Flow, as detailed in the companion paper (Lowe et al., 2005).
Gaku Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of heat transportation by Oscillatory Flow in a curved tube
International Journal of Heat and Mass Transfer, 2014Co-Authors: Gaku Tanaka, Kosuke Shiratori, Seiichiro Yuguchi, Hong YuAbstract:Abstract The present paper deals with the longitudinal heat transportation by an Oscillatory Flow in a curved tube heat transportation pipe. The velocity and temperature fields during Oscillatory water Flow in a curved tube with inner diameter of 10 mm were numerically simulated using the commercial software FLUENT. To clarify the effect of the curvature on heat transportation, the ratio of the tube radius to the curvature radius was varied from 0.0125 to 0.075, and Oscillatory Flow frequency was varied from 0.1 to 2.0 Hz. The effective thermal diffusivity exhibited a peak at a curvature ratio around 0.05–0.07 and reached a value 12 times higher than that of a straight tube. It was also found that the dispersion of fluid particles due to secondary Flow caused the enhancement of heat transportation.
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Heat transportation by Oscillatory Flow with steady Flow component
Heat Transfer Research, 2006Co-Authors: Akira Inukai, Mitsugu Takahashi, Makoto Hishida, Gaku TanakaAbstract:This paper deals with heat transportation by an Oscillatory Flow composed of a sinusoidal Oscillatory Flow superimposed with a steady Flow. Velocity and temperature fields, heat transportation rate, work rate, and heat transportation efficiency were investigated through numerical analysis. Results obtained elucidated that (1) the phase difference between velocity and temperature variation remained the same as that of the sinusoidal reciprocal Flow without the use of a steady Flow component. (2) In the upstream direction heat was mainly transported by the steady Flow component and in the downstream direction transportation was mainly performed by the Oscillatory Flow component. (3) The heat transportation rate of the present Oscillatory Flow composed of both steady and Oscillatory Flow components was less than the arithmetic sum of the rates produced by the steady Flow and the sinusoidal Oscillatory Flow. (4) The heat transportation rate was increased immensely by superimposing the steady Flow on the sinusoidal Oscillatory Flow. (5) Conversely, work done by the present Oscillatory Flow increased only slightly. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 482–500, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20130
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Oscillatory Flow in loop channel with right angle branch and reservoirs
Jsme International Journal Series B-fluids and Thermal Engineering, 2006Co-Authors: Daisuke Takahashi, Gaku Tanaka, Daisuke Akazawa, Makoto HishidaAbstract:Oscillatory Flow in loop channels consisting of a T-branch, two reservoirs, and main and side branches was experimentally investigated. The following were found: (1) Oscillatory Flow composed of Oscillatory and steady components was induced in the loop channels. (2) The ratio of the Flow rate of the steady component in the main and side branches to the maximum Flow rate of Oscillatory Flow in the primary branch approached constant values in the Reynolds number range of 5 000 < Re p,max ≤ 10 000. (3) Time-averaged pressure differences were generated between the two exits of the T-branch and between the inside and outside of the reservoirs. These pressure differences induced the steady component in the Oscillatory Flow in the loop channel. (4) The ratio of the Flow rate of the Oscillatory component in the main branch to that in the side branch was nearly equal to the ratio of the reciprocal lengths of the main and side branches.
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Secondary Flow Augmentation during Intermittent Oscillatory Flow in Model Human Central Airways
Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing, 2001Co-Authors: Gaku Tanaka, Kazuo TanishitaAbstract:The efficiency of axial gas dispersion during ventilation with high-frequency oscillations (HFO) can be improved by manipulating the Oscillatory Flow waveform such that intermittent Oscillatory Flow occurs. To clarify the augmentation of axial gas transfer during intermittent Oscillatory Flow, we measured the axial and secondary velocity profiles during intermittent Oscillatory Flow through a model human central airway. We used a rigid model of human airways consisting of asymmetrical bifurcations up to third generation. Velocities in the axial and radial directions were measured with two-color laser-Doppler velocimetry. Secondary Flow was accelerated at the beginning of the stationary period, particularly in the trachea, which resulted in enhanced gas transport during intermittent Oscillatory Flow.
S Srinivas - One of the best experts on this subject based on the ideXlab platform.
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a note on heat transfer to mhd Oscillatory Flow in an asymmetric wavy channel
International Communications in Heat and Mass Transfer, 2010Co-Authors: R Muthuraj, S SrinivasAbstract:This note deals with the MHD Oscillatory Flow of an optically thin fluid in an asymmetric wavy channel filled with porous medium. Based on some simplifying assumptions, the governing momentum and energy equations are solved and analytical solutions for fluid velocity, temperature distribution, Nusselt number and skin friction are constructed. The effects of radiation parameter, Peclet number, Hartmann number, porous medium shape factor and geometric parameters on Flow and heat transfer characteristics have been examined in detail.
