The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Ajay K. Ray - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of Taylor Vortex photocatalytic reactor for water purification
Chemical Engineering Science, 2004Co-Authors: Paritam K. Dutta, Ajay K. RayAbstract:A Taylor Vortex photocatalytic reactor was developed that creates unsteady Taylor–Couette flow in between the two co-axial cylinders by re-circulating fluids form bulk to the inner cylinder wall, which was coated with TiO2. Systematic investigation for flow development as well as photocatalytic degradation of three different organic compounds was carried out. The effect of Reynolds number and catalyst loading on photocatalytic degradation were compared for both slurry and fixed catalyst system. The experimental results demonstrate that Taylor Vortex photocatalytic reactor is promising for water purification even when catalyst is fixed, as there is no significant difference in overall degradation rate between slurry and immobilized systems.
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A Taylor Vortex Photocatalytic Reactor for Water Purification
Industrial & Engineering Chemistry Research, 2001Co-Authors: Tapan K. Sengupta, Mohammad F. Kabir, Ajay K. RayAbstract:A detailed analysis has been performed for a heterogeneous photocatalytic Taylor Vortex reactor that uses flow instability to recirculate fluid continually from the vicinity of the rotating inner cylindrical surface to the stationary outer cylindrical surface of an annulus. In the present research, a detailed time-accurate computation shows the different stages of flow evolution and the effects of the finite length of the reactor in creating eddies, which results in a very high overall efficiency of photocatalytic conversion. The physical arrangement considered is such that pollutant degradation is maximized by the motion of fluid particles in a specific regime of centrifugal instability. Also provided are detailed flow structures for the chosen parameters when the reactor is started impulsively.
Woo-sik Kim - One of the best experts on this subject based on the ideXlab platform.
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Influence of Fluid Motions on Polymorphic Crystallization of l-Histidine: Taylor Vortex Flow and Turbulent Eddy Flow
Crystal Growth & Design, 2018Co-Authors: Suna Park, Woo-sik KimAbstract:The mechanistic influence of fluid motions, such as a Taylor Vortex flow and turbulent eddy flow, on the polymorphic crystallization of l-histidine was investigated. Couette–Taylor (CT) and mixing tank (MT) crystallizers were used for the Taylor Vortex flow and turbulent eddy flow, respectively. Due to its periodic fluid motion, the Taylor Vortex flow was found to be more favorable than the turbulent eddy flow for polymorphic nucleation of the stable phase. Thus, the polymorphic fraction of the stable phase at the induction point (called the “initial stable polymorphic fraction”) in the CT crystallizer was always much higher than that in the MT crystallizer for all variations of the crystallization conditions, including the rotation/agitation speed, ethanol fraction in the mixture solvent, and cooling rate. When increasing the rotation speed of the inner cylinder in the CT crystallizer, the initial stable polymorphic fraction was significantly increased and reached 100% at a rotation speed above 700 rpm. ...
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Batch Cooling Crystallization in Non-Isothermal Taylor Vortex Flow: Effective Method for Controlling Crystal Size Distribution
Crystal Growth & Design, 2016Co-Authors: Hyun Kim, Woo-sik KimAbstract:A non-isothermal Taylor Vortex fluid motion was applied for effective control of the crystal size distribution (CSD) in batch cooling crystallization without seed crystals. The non-isothermal Taylor Vortex fluid motion was generated using different cylinder temperatures, i.e., a hot inner cylinder and cold outer cylinder, in a Couette–Taylor (CT) crystallizer. Thus, an internal loop of heating dissolution of crystals on the inner cylinder and cooling recrystallization on the outer cylinder was created in the gap between the two cylinders by the Taylor Vortex fluid motion. As a result, the crystal size distribution can be effectively controlled by adjusting the operating parameters, including the temperature difference between the inner and outer cylinders, rotation speed of the inner cylinder, and cooling rate in the CT crystallizer. When increasing the temperature difference, the mean crystal size becomes larger and the CSD becomes narrower. Meanwhile, increasing the rotation speed enlarges the mean crys...
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Polymorphic Crystallization of Sulfamerazine in Taylor Vortex Flow: Polymorphic Nucleation and Phase Transformation
Crystal Growth & Design, 2015Co-Authors: Sun-ah Park, Sun Lee, Woo-sik KimAbstract:The influence of a periodic Taylor Vortex flow on the polymorphic crystallization of sulfamerazine (SMZ), including polymorphic nucleation and phase transformation, was investigated using a Couette–Taylor (CT) crystallizer, and also compared with the influence of a random turbulent flow in a mixing tank (MT) crystallizer. In the MT crystallizer, the induction of the metastable phase (form-I) occurred first, which was then followed by the induction of the stable phase (form-II) 10–85 h later. However, this whole process was significantly reduced to a half hour in the CT crystallizer, demonstrating the high efficiency of a Taylor Vortex flow for the induction of polymorphic nucleation. The efficiency of the Taylor Vortex flow was also enhanced when increasing the rotation speed. As a result, the stable and metastable phases were simultaneously nucleated at the first induction with a rotation speed above 300 rpm; plus the stable-phase fraction nucleated at the first induction increased when increasing the ro...
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Agglomeration of Ni-rich hydroxide in Conical Taylor Vortex flow
2015Co-Authors: Quemé-peña Mayra, Hwayong Kim, Woo-sik KimAbstract:As a precursor of the cathode material for Li-ion battery is presented in this study the Ni-rich hydroxide. One of the most critical factors determining the electrical capacity of the cathode is the tap density which depends on a spherical shape and uniform size distribution. The agitation and dispersion medium are important factors for the agglomeration of crystals because generally determine the collision and physical adhesion between crystals. Thus, the agglomeration depends on the hydrodynamics conditions of the fluid, which determine the size and morphology of the crystal. In this study the conical Taylor Vortex flow in the non-constant gap width of the Couette-Taylor crystallizer was investigated for the agglomeration of Ni-rich hydroxide. The meridional flow, which considerably influences the vortices, is not uniform, because of the different gap cross-sections along the axial position of the crystallizer. This results in a three-dimensional flow, which has a crucial influence on the produced vortices. Thus, the geometry crucially affects the flow and the occurring vortices, as it was demonstrated in the case of the classical Couette-Taylor arrangement (concentric cylinders) with different gap width. In this study, the apex angle between the inner and outer cylinder as well as the rotation speed and direction of the inner conical cylinder were varied in order to investigate the influence of the Taylor Vortex flow regime on the agglomeration of Ni-rich hydroxide with regarding to the particle size, distribution and shape, in order to get spherical agglomerate particles with narrow size distribution and higher tap density.
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Agglomeration of Ni-rich hydroxide crystals in Taylor Vortex flow
Powder Technology, 2015Co-Authors: Dien Khuong Thai, Quemé-peña Mayra, Woo-sik KimAbstract:Abstract The agglomeration of Ni-rich hydroxide crystals (Ni0.9Co0.05Mn0.05)(OH)2 was studied in a continuous Couette-Taylor (CT) crystallizer. Due to the excellent mixing and periodic fluid motion of the Taylor Vortex flow in the CT crystallizer, the formation of spherical and uniform agglomerate particles of Ni-rich crystals was promoted as the rotation speed and the mean residence time increased. Thus, for a rotation speed of 1500 rpm and mean residence time of 60 min, with a high feed concentration of 3.0 mol/L produced a high tap-density of agglomerate particles of 2.13 g/cm3, which is higher than any previously reported values. These results were due to the excellent micromixing effects of Taylor Vortex in the CT crystallizer. In addition, the long mean residence time contributed to the formation of spherical particles due to the extended exposure of the agglomerates to the fluid shear. Furthermore, the formation of spherical particles was optimized at a pH of 12.0 and required a high concentration of ammonia due to the high composition of Ni ions in the Ni-rich hydroxide crystals and the short mean residence time in the continuous CT crystallizer. Moreover, when comparing the crystallization in a continuous MSMPR crystallizer, which required a long mean residence time of 12 h for a high tap-density of above 2.0 g/cm3, the continuous CT crystallizer was clearly much more effective for the formation of uniform spherical particles due to the more efficient hydrodynamic fluid motion of the Taylor Vortex in the CT crystallizer in contrast to the random turbulent eddy motion in the MSMPR crystallizer.
Y. T. Chew - One of the best experts on this subject based on the ideXlab platform.
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Second Taylor Vortex flow: Effects of radius ratio and aspect ratio
Physics of Fluids, 2002Co-Authors: Qing Xiao, Tee Tai Lim, Y. T. ChewAbstract:This paper is motivated by our earlier investigation on the stability of Taylor–Couette flow in which we discovered a previously unidentified flow regime, which we refer to as “Second Taylor Vortex flow” (STVF) when an inner cylinder is subjected to some critical acceleration [Lim, Chew, and Xiao, Phys. Fluids 10, 3233 (1998)]. The aim here is to explore how the STVF regime is affected by changes in radius ratio and aspect ratio. Results show that the STVF regime is sensitive to the gap size between the two cylinders, and does not exist for some radius ratios, whereas it increases with decreasing aspect ratio.
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Effect of acceleration on the wavy Taylor Vortex flow
Experiments in Fluids, 2002Co-Authors: Qing Xiao, Tee Tai Lim, Y. T. ChewAbstract:In this paper, we use a laser optical technique to investigate the characteristics of a wavy Taylor Vortex flow between two concentric cylinders, with the inner cylinder subjected to a wide range of predetermined acceleration and the outer one at rest. We focus on the inner/outer radius ratio of 0.894, with an acceleration (dRe/dt*) from 0.1123 to 2,247, and Reynolds number from Re/Re c =1.0 to 36. The results show that, with increasing Reynolds number, there is an initial increase in the wavelength of the wavy Vortex flow (λ), and a decrease in the wave speed (c) before they asymptote to a constant value, which is a function of the acceleration. As for the wave amplitude (A), it is found that the effect of acceleration is significant only in a very narrow range of Reynolds numbers.
R. Dennis Vigil - One of the best experts on this subject based on the ideXlab platform.
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Jet breakup regimes in liquid–liquid Taylor Vortex flow
International Journal of Multiphase Flow, 2020Co-Authors: Charlton Campbell, Michael G. Olsen, R. Dennis VigilAbstract:Abstract Optical experiments were used to identify breakup regimes for a liquid jet injected into in a second immiscible liquid undergoing turbulent Taylor Vortex flow. Four jetting breakup behaviors were observed and these were compared with analogous jetting regimes in quiescent liquid-liquid systems as well as liquid-gas systems with a gaseous crossflow. Several jet breakage regime maps for liquid–liquid Taylor Vortex flow were generated using jet Reynolds number, Ohnesorge number, crossflow Weber number, and momentum flux ratio as organizing parameters. However, selection of the breakup mechanism was found to depend primarily on the jet Reynolds number and was largely independent of parameters characterizing the fluid crossflow, such as the azimuthal Reynolds number and crossflow Weber number. This finding is consistent with previous observations that the downstream droplet size distribution in Taylor Vortex flow is relatively insensitive to parameters other than the jet Reynolds number. Lastly, the transitions between the four identified jet breakage regimes were found to be coincident with changes in the mean droplet size observed downstream from the inlet jet.
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Characteristic time scales of mixing, mass transfer and biomass growth in a Taylor Vortex algal photobioreactor.
Bioresource technology, 2015Co-Authors: Xi Gao, Bo Kong, R. Dennis VigilAbstract:Recently it has been demonstrated that algal biomass yield can be enhanced using fluid flow patterns known as Taylor vortices. It has been suggested that these growth rate improvements can be attributed to improved light delivery as a result of rapid transport of microorganisms between light and dark regions of the reactor. However, Taylor vortices also strongly impact fluid mixing and interphase (gas-liquid) mass transport, and these in turn may also explain improvements in biomass productivity. To identify the growth-limiting factor in a Taylor Vortex algal photobioreactor, experiments were performed to determine characteristic time scales for mixing and mass transfer. By comparing these results with the characteristic time scale for biomass growth, it is shown that algal growth rate in Taylor Vortex reactors is not limited by fluid mixing or interphase mass transfer, and therefore the observed biomass productivity improvements are likely attributable to improved light utilization efficiency.
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Light‐limited continuous culture of Chlorella vulgaris in a Taylor Vortex reactor
Environmental Progress & Sustainable Energy, 2013Co-Authors: Bo Kong, R. Dennis VigilAbstract:Recently, it has been demonstrated that Taylor vortices—hydrodynamic structures that arise in the annular region between two concentric cylinders when the inner cylinder rotates—can substantially improve the growth rate of algal biomass in a batch photobioreactor by inducing the flashing light effect. In order to assess the potential for using Taylor Vortex flow to continuously culture algae, experiments were carried out in a continuous flow Taylor Vortex algal photobioreactor using Chlorella vulgaris. Specifically, two important operating parameters were varied: the dilution rate and the inner cylinder rotation speed. For a fixed inner cylinder rotation speed, biomass productivity was independent of dilution rate. In contrast, biomass productivity was found to increase with increasing inner cylinder rotation speed for a fixed dilution rate, but this effect became less pronounced at higher rotation speeds. Overall, it is demonstrated that a continuous flow Taylor Vortex algal photobioreactor can be used to produce and sustain high biomass production and carbon dioxide capture rates when operated in continuous flow mode. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 884–890, 2013
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Enhanced algal growth rate in a Taylor Vortex reactor.
Biotechnology and bioengineering, 2013Co-Authors: Bo Kong, Jacqueline V. Shanks, R. Dennis VigilAbstract:The rate of production of algal biomass in optically dense photobioreactors depends crucially on the temporal light exposure of microorganisms, which in turn is determined by fluid flow patterns and the quantity and spatial distribution of photosynthetically active radiation. In this report it is demonstrated that highly organized and robust toroidal flow structures known as Taylor vortices cause significant increases in the rate of biomass production, efficiency of light utilization, and CO2 uptake, and these effects become more pronounced at higher Reynolds numbers. In light of these findings and previously reported experiments using Taylor Vortex flow to culture algae, it is argued that the flashing light effect, rather than mass transport effects, is responsible for the observed increases in the rate of photosynthesis.
Carlo F. Barenghi - One of the best experts on this subject based on the ideXlab platform.
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Transition from Ekman flow to Taylor Vortex flow in superfluid helium
Journal of Fluid Mechanics, 2004Co-Authors: Karen Henderson, Carlo F. BarenghiAbstract:By numerically computing the steady axisymmetric flow of helium II confined inside a finite-aspect-ratio Couette annulus, we determine the transition from Ekman flow to Taylor Vortex flow as a function of temperature and aspect ratio. We find that the low-Reynolds-number flow is quite different to that of a classical fluid, particularly at lower temperatures. At high aspect ratio our results confirm the existing linear stability theory of the onset of Taylor vortices, which assumes infinitely long cylinders. © 2004 Cambridge University Press.
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Numerical methods for two-fluid hydrodynamics: Application to the Taylor Vortex flow of superfluid helium II
Journal of Low Temperature Physics, 1995Co-Authors: Karen L. Henderson, Carlo F. BarenghiAbstract:We describe the numerical method which we have developed to solve for the first time the fully nonlinear HVBK equations. These equations generalise Landau's two fluid model to take into account the presence of quantised vortices. We apply the method to investigate the flow pattern of helium II between rotating concentric cylinders (Taylor Vortex flow) at increasing Reynolds numbers. We compare the results against classical Taylor Vortex flow.