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Jamal Chaouki - One of the best experts on this subject based on the ideXlab platform.

  • Development and confirmation of a simple procedure to measure solids distribution in fluidized beds using tracer Particles
    Chemical Engineering Science, 2020
    Co-Authors: Xi Gao, Jamal Chaouki, Jonathan Seville, Sina Tebianian, Thomas Leadbeater, Rouzbeh Jafari, John Grace, David Parker, Naoko Ellis
    Abstract:

    The spatial distribution of solid Particles is a key factor affecting the performance of fluidized bed reactors. Non-invasive techniques including Radioactive Particle tracking (RPT) and positron emission Particle tracking (PEPT) are deployed to measure the solids distribution. Different methods to calibrate the Particle tracking measurements have been developed to quantify mean solids concentration. In this paper, gas-solid flows in a traveling fluidized bed are simulated with CFD-DEM and the behavior of different Particles, including bulk sand Particles and tracer Particles are investigated. The simulated hydrodynamics are compared with experimental measurements. Analyses are carried out to derive the mean solids concentration from the tracer Particle data. Different calibration approaches are examined, and the simple calibration method is verified. It is shown that the mean solids concentration can be measured reliably using representative tracer Particles. The experimental RPT data are then revisited with the new calibration method which yields more realistic results.

  • Numerical and experimental comparison of tracer Particle and averaging techniques for Particle velocities in a fluidized bed
    Chemical Engineering Science, 2019
    Co-Authors: Sina Tebianian, Jamal Chaouki, Jonathan Seville, Naoko Ellis, Thomas Leadbeater, David Parker, Rouzben Jafari, John Grace
    Abstract:

    Particle tracking methods using emitted radiation are attractive for following motion in opaque systems such as granular materials. Leading examples are Positron Emission Particle Tracking (PEPT) and Radioactive Particle Tracking (RPT). The application of such techniques sometimes requires the use of tracer Particles which differ in size, density and/or shape from the Particles of interest. This study investigates the extent to which such differences affect the result of the study by using the open source MFIX-DEM software to model Particle motion in the travelling fluidized bed experiments. The results are compared with previously reported experimental studies using both PEPT and RPT. Consistent numerical results were obtained for both PEPT and RPT tracer Particles. In determining averaged velocities using such techniques, there is a choice to be made between averaging velocities of Particles crossing a virtual plane over a period of time (the "face-average" approach) or those passing through a defined volume over time (the "volume-average" approach). The differences between results obtained with these two approaches are shown to be significant in this case, for both computation and experiment.

  • investigating the dynamics of cylindrical Particles in a rotating drum using multiple Radioactive Particle tracking
    Aiche Journal, 2016
    Co-Authors: Majid Rasouli, François Bertrand, Olivier Dube, Jamal Chaouki
    Abstract:

    The behavior of granular flows inside rotating drums is an ongoing area of research. Only a few studies have investigated non-spherical Particles despite the fact that Particle shape is known to have a significant impact on flow behavior. In addition, the experimental techniques limit the interpretation of the results of these studies. In this work, we compared the flow behavior of cylindrical and spherical Particles using the multiple Radioactive Particle tracking technique to capture the positions and orientations of cylindrical Particles simultaneously. We analyzed two important components of the transverse flow dynamics, that is, the boundary between the active and passive layers, and the velocity profile on the free surface. For the cylindrical Particles, two general models are proposed to calculate the velocity profiles on the free surface and the effective Particle sizes in the active and passive layers. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2622–2634, 2016

  • comparison of Particle velocity measurement techniques in a fluidized bed operating in the square nosed slugging flow regime
    Powder Technology, 2016
    Co-Authors: Sina Tebianian, Jamal Chaouki, Kristian L Dubrawski, Naoko Ellis, Ray Cocco, Roy Hays, S Reddy B Karri, Thomas Leadbeater, David J Parker, Rouzbeh Jafari
    Abstract:

    Abstract The novel “travelling fluidized bed” (TFB), operated under identical conditions, was deployed to compare alternate experimental measurement techniques for the investigation of solid motion in gas-fluidized beds operating in the square-nosed slugging regime. Measurements of Particle velocity obtained by Radioactive Particle tracking (RPT — non-invasive at the Ecole Polytechnique de Montreal), positron emission Particle tracking (PEPT — non-invasive at University of Birmingham), optical fibre probes (invasive at UBC) and borescopic high speed Particle image velocimetry (invasive at PSRI) are compared for sand Particles of mean diameter of 292 μm. Significant differences between the time-average radial profiles of Particle velocity are observed in many cases. The results provide valuable insights into the merits and challenges of advanced Particle velocity measurement techniques.

  • experimental investigation of solid Particles flow in a conical spouted bed using Radioactive Particle tracking
    Aiche Journal, 2016
    Co-Authors: Laurent Spreutels, François Bertrand, Benoit Haut, Robert Legros, Jamal Chaouki
    Abstract:

    Solid Particles flow in a conical spouted bed is characterized by Radioactive Particle tracking. The influence of operating conditions on key parameters of this flow is evaluated and discussed: the morphology of the solid bed is not strongly influenced by the forces exerted by the gas on the solid Particles, but rather by geometrical considerations; the Particles spend approximately 8% of their time in the spout in all experiments; it is the force exerted on the solid Particles by the gas that directly controls the volumetric flow rate between adjacent regions, and not the amount of Particles in the bed; as U/Ums increases, the volume of solid Particles in the annulus decreases, the volume of solid Particles in the fountain increases and the volume of solid Particles in the spout remains constant. Correlations to predict key flow parameters as functions of operating conditions are also established and discussed. © 2015 American Institute of Chemical Engineers AIChE J, 2015

Muthanna H Aldahhan - One of the best experts on this subject based on the ideXlab platform.

  • investigation of hydrodynamics of binary solids mixture spouted beds using Radioactive Particle tracking rpt technique
    Chemical Engineering Research & Design, 2019
    Co-Authors: Thaar Aljuwaya, Neven Ali, Muthanna H Aldahhan
    Abstract:

    Abstract The hydrodynamic and mixing behavior of binary solids mixture spouted beds with Particles of the same size but different densities have been investigated experimentally in gas–solid spouted beds for the first time, using an advanced non-invasive Radioactive Particle tracking (RPT) technique. The RPT experiments have been performed for different composition of binary mixture at different superficial gas velocity. The binary solids mixture used in the experiment consists of glass beads and steel Particles of densities 2500 and 7400 kg/m3, respectively. The RPT experiments were carried out for each one of the solids phases on an individual basis, and then the statistical averages of each flow fields are combined together to formulate the entire picture of the binary solids mixture flow field. It was found that segregation always takes place in the spout due to the dissimilar behavior between the different solids phases in terms of the solids velocity field and turbulent parameters. The results also demonstrated that for the hydrodynamics of binary solids mixture spouted beds which have Particles of similar size but different densities, the Particle–Particle interaction plays an important role, but it does not dominate the gas–Particle interaction, and each contributes to the extent of the mixing and segregation phenomena inside the bed. The results and findings of our work are valuable in understanding the hydrodynamics of the binary solids mixture encountered in the gas–solid spouted beds of TRISO nuclear fuel Particles and provide benchmark data to validate computational fluid dynamics (CFD).

  • mapping of microalgae culturing via Radioactive Particle tracking
    Chemical Engineering Science, 2018
    Co-Authors: Abbas Jawad Sultan, Muthanna H Aldahhan, Laith S Sabri
    Abstract:

    Abstract In this study, an advanced Radioactive Particle tracking (RPT) technique was used to investigate for the first time the details of the cells’ movements (trajectory) and multiphase flow hydrodynamics during microalgae culturing in a cylindrical split airlift photobioreactor. The cells’ trajectory, liquid velocity field, distributions of shear stresses, and the turbulent kinetic energy field were studied under superficial gas velocity of 1 and 3 cm/s. The structures of the flow in the whole reactor, the riser, the downcomer, as well as the structure above and below the split plate were characterized. The effects of the cells’ concentration and different aeration rate at different axial levels on the studied parameters were discussed. It has been found that the cells’ fluctuations reduced and its movement frequency between the light (wall) and dark zone decreased during the culturing particularly when the cells concentrations becomes large after 30 days of culturing. Distinguishing behaviors were observed for all the parameters, with a higher magnitude at the superficial gas velocity 3 cm/sec than at 1 cm/sec. This effect positively enhanced the liquid circulation and the movement between the reactor sides, the riser, and the downcomer. This circulation and good mixing phenomena had a large positive impact on the culture’s continuity. The obtained results are reliable as benchmark data to validate computational fluid dynamics (CFD) simulation and other models that can be later used to be integrated with dynamic growth and light intensity models for optimized.

  • an advanced evaluation of the mechanistic scale up methodology of gas solid spouted beds using Radioactive Particle tracking
    Particuology, 2017
    Co-Authors: Neven Ali, Thaar Aljuwaya, Muthanna H Aldahhan
    Abstract:

    Abstract We implemented for the first time our Radioactive Particle tracking as an advanced noninvasive technique to further evaluate and validate our newly developed mechanistic scale-up methodology based on matching the radial profile of the gas holdup. Two spouted beds with diameters of 0.076 and 0.152 m were used. Three sets of conditions were implemented; i.e., conditions of the reference case, conditions that provided a gas-holdup radial profile similar to that of the reference case, and conditions that provided a gas-holdup radial profile dissimilar to that of the reference case. The results confirm the validation of the scale-up methodology in terms of obtaining closer dimensionless values and radial profiles of components of the Particle velocity, normal stress, shear stress, and turbulent kinetic energy. The results further advance the understanding of gas–solids spouted beds, provide deeper insight into the solids dynamics of the beds and present important benchmarking data for validating computational fluid dynamics codes and models.

  • study the effect of dense internals on the liquid velocity field and turbulent parameters in bubble column for fischer tropsch ft synthesis by using Radioactive Particle tracking rpt technique
    Chemical Engineering Science, 2017
    Co-Authors: Mohammed Al K Mesfer, Abbas Jawad Sultan, Muthanna H Aldahhan
    Abstract:

    Abstract In this study, the effects of the dense vertical internals on the liquid velocity field and turbulence parameters (Reynolds stresses, turbulent kinetic energy, and turbulent eddy diffusivities) are experimentally investigated for the first time by using advanced Radioactive Particle Tracking (RPT) technique. The experimental work was carried out in a Plexiglas bubble column with 5.5 in. (0.14 m) and a height of 72 in. (1.83 m) for the air-water system. In this work, thirty vertical Plexiglass internals of 0.5 in. (0.0127 m) outer diameter were used which covered ∼25% (typical for Fischer–Tropsch processes) of the total cross-sectional area of the column where they arranged as the triangular pitch of 0.84 in. (0.0214 m). The superficial gas velocities based on both total cross-sectional area and free cross-sectional area available for the flow were utilized (0.08, 0.2, and 0.45 m/s), which covered the transition and churn-turbulent flow regime to meet the industrial applications of FT synthesis. The experimental data show that the presence of the internals at a given superficial gas velocity causes an increase in the axial centerline liquid velocity and a sharp decrease in turbulence parameters while the increase in superficial gas velocity in the presence of internals causes an increase in axial centerline liquid velocity and turbulent parameters. The obtained data are reliable as a benchmark data for validation computational fluid dynamics (CFD) simulation, and models.

  • bed diameter effect on the hydrodynamics of gas solid fluidized beds via Radioactive Particle tracking rpt technique
    Canadian Journal of Chemical Engineering, 2017
    Co-Authors: Abdelsalam Efhaima, Muthanna H Aldahhan
    Abstract:

    The hydrodynamics observed in large-scale gas-solid fluidized bed reactors are different from those observed in smaller scale beds. In this study, the effect of bed diameter on the hydrodynamics of gas-solid fluidized bed reactors has been investigated in two bubbling fluidized beds of 44 cm and 14 cm in diameter using an advanced non-invasive Radioactive Particle tracking (RPT) technique. Compressed air at room temperature was used as the gas phase, and the solid was glass beads with a Particle size of 210 μm (Geldart-B) and density of 2.5 g · cm−3. Particle velocity field, Reynolds stresses, normal stresses, turbulent kinetic energy, and axial and radial eddy diffusivities were measured in two beds at gas velocities of 1.5 Umf, 2 Umf, and 3 Umf. Experimental results showed that the bed scales have a significant effect on some of these hydrodynamic parameters where the magnitude of solids velocity is much higher in the larger bed and the solids mixing and diffusion of Particles are increased by increasing the column diameter.

Rajesh K. Upadhyay - One of the best experts on this subject based on the ideXlab platform.

  • Methods of preparation of microParticles for Radioactive Particle tracking experiments
    Applied radiation and isotopes : including data instrumentation and methods for use in agriculture industry and medicine, 2020
    Co-Authors: Jayashree Biswal, Rajesh K. Upadhyay, Sunil Goswami, Harish J. Pant
    Abstract:

    Abstract Radioactive Particle tracking (RPT) technique is a relatively newer technique for the characterization of flow of process materials (liquids, solids) in laboratory- and pilot-scale industrial systems. The technique uses a single Particle labelled with a suitable radioisotope having similar physical properties to that of the bulk of the process material. The preparation of a representative Radioactive microParticle is a challenging task in the implementation of the technique. There are no standard methods available for the preparation of Radioactive microParticles. This paper discusses some of the methods of preparation of Radioactive microParticles for RPT studies. A few examples of RPT applications using the prepared microParticles are also discussed.

  • time series analysis of a binary gas solid conical fluidized bed using Radioactive Particle tracking rpt technique data
    Chemical Engineering Journal, 2019
    Co-Authors: Lipika Kalo, H J Pant, Miryan Cassanello, Rajesh K. Upadhyay
    Abstract:

    Abstract In current work, the Radioactive Particle tracking (RPT) technique has been used to investigate the behavior of gas-solid conical mono and binary fluidized bed. The dynamics of the bed has been analyzed using both time-averaged and fluctuation quantities at different gas inlet velocities and bed compositions. The binary bed was composed of glass beads of two different diameters 1 mm and 0.6 mm. The bed of 0:100, 50:50 and 100:0 by wt % of both the Particles were investigated. Time-averaged quantities like mean axial velocities, RMS velocities, and granular temperature indicate that behavior of conical bed at the top and bottom sections are significantly different. Gas-solid interactions mainly dominate the bottom section while Particle-Particle interaction plays a critical role at the top section. Further, time series and chaos analysis of RPT data were performed. Hurst exponent, autocorrelation coefficient, and mixing index were calculated through time series analysis. The results indicate that better mixing is observed in conical bed even at low velocity compared to cylindrical fluidized-bed. It also reveals a regime transition around 5.7 m/s gas inlet velocity. Finally, Kolmogorov entropy and correlation dimension calculated through chaos analysis of RPT data confirm flow regime transition at gas inlet velocity around 5.7 m/s, for all the examined bed compositions.

  • Experimental and numerical investigation of liquid–solid binary fluidized beds: Radioactive Particle tracking technique and dense discrete phase model simulations
    Particuology, 2017
    Co-Authors: Varsha Jain, Harish J. Pant, Lipika Kalo, Deepak Kumar, Rajesh K. Upadhyay
    Abstract:

    Abstract Liquid–solid binary fluidized beds are widely used in many industries. However, the flow behavior of such beds is not well understood due to the lack of accurate experimental and numerical data. In the current study, the behavior of monodisperse and binary liquid–solid fluidized beds of the same density but different sizes is investigated using Radioactive Particle tracking (RPT) technique and a dense discrete phase model (DDPM). Experiments and simulations are performed in monodisperse fluidized beds containing two different sizes of glass beads (0.6 and 1 mm) and a binary fluidized bed of the same Particles for various bed compositions. The results show that both RPT and DDPM can predict the mixing and segregation pattern in liquid–solid binary fluidized beds. The mean velocity predictions of DDPM are in good agreement with the experimental findings for both monodisperse and binary fluidized beds. However, the axial root mean square velocity predictions are only reasonable for bigger Particles. Particle–Particle interactions are found to be critical for predicting the flow behavior of solids in liquid–solid binary fluidized beds.

  • experimental and numerical investigation of liquid solid binary fluidized beds Radioactive Particle tracking technique and dense discrete phase model simulations
    Particuology, 2017
    Co-Authors: Varsha Jain, H J Pant, Lipika Kalo, Deepak Kumar, Rajesh K. Upadhyay
    Abstract:

    Abstract Liquid–solid binary fluidized beds are widely used in many industries. However, the flow behavior of such beds is not well understood due to the lack of accurate experimental and numerical data. In the current study, the behavior of monodisperse and binary liquid–solid fluidized beds of the same density but different sizes is investigated using Radioactive Particle tracking (RPT) technique and a dense discrete phase model (DDPM). Experiments and simulations are performed in monodisperse fluidized beds containing two different sizes of glass beads (0.6 and 1 mm) and a binary fluidized bed of the same Particles for various bed compositions. The results show that both RPT and DDPM can predict the mixing and segregation pattern in liquid–solid binary fluidized beds. The mean velocity predictions of DDPM are in good agreement with the experimental findings for both monodisperse and binary fluidized beds. However, the axial root mean square velocity predictions are only reasonable for bigger Particles. Particle–Particle interactions are found to be critical for predicting the flow behavior of solids in liquid–solid binary fluidized beds.

  • investigation of liquid solids fluidized bed of different Particle size through Radioactive Particle tracking techniques
    Journal of Radioanalytical and Nuclear Chemistry, 2014
    Co-Authors: Shubham Jain, H J Pant, Priyam Saraswat, Varsha Jain, Rajesh K. Upadhyay
    Abstract:

    Radioactive Particle tracking technique (RPT) has proven to be a powerful and versatile technique both in terms of the richness of information it provides as well as the variety of multiphase flow situations it has been successfully employed. This work reports the execution of RPT technique for investigation of liquid–solids fluidized bed of different Particle sizes (1.2 and 0.6 mm). Experiments are performed in a 10 cm ID cylindrical column for different liquid velocities. Further, RPT experiments are performed for both the solids and effect of liquid velocity and Particle size on flow behaviour of liquid–solid fluidized bed is quantified.

Shantanu Roy - One of the best experts on this subject based on the ideXlab platform.

  • investigation of hydrodynamics in bubble column with internals using Radioactive Particle tracking rpt
    Aiche Journal, 2017
    Co-Authors: Dinesh V Kalaga, H J Pant, Sameer V Dalvi, J B Joshi, Shantanu Roy
    Abstract:

    Even though many experimental investigations are reported on this subject of liquid velocity patterns in bubble columns, most of the reported work is restricted to measurements at the near wall regions, columns without internals, and in low dispersed phase holdups. In the present work, a non-invasive Radioactive Particle Tracking (RPT) technique was employed to quantify the hydrodynamic parameters in 120 mm diameter bubble column with, and without vertical rod internals, using air/water system as the working fluids. The superficial air velocities cover a wide range of flow regimes: from 14 mm/s to 265 mm/s. Experiments were performed for four internals configurations with percentage obstruction area varied from 0 (without internals) to 11.7%. We report that the liquid phase hydrodynamics depends strongly on superficial gas velocity and internals. This article is protected by copyright. All rights reserved.

  • investigation of two phase oil water flow in coiled geometries using Radioactive Particle tracking time of flight rpt tof and Radioactive Particle tracking volume fraction rpt vof measurements
    Chemical Engineering Science, 2017
    Co-Authors: Loveleen Sharma, K D P Nigam, Shantanu Roy
    Abstract:

    Abstract In this work, the characteristics of two-phase oil-water flow through a coiled tube geometry have been investigated. Radial mixing, local volume fractions, and phase holdup, over a range of Reynolds numbers of either phase, have been presented. The specific novelty of this work has been the use of time-of-flight (TOF) and volume fraction (VOF) measurements for a single Radioactive Particle, marked in turn, to represent the flow in either of the phases. This use of the RPT-TOF and RPT-VOF to investigate two-phase oil-water flow has never been reported thus far. In our measurements, a γ-ray emitting radiotracer was made neutrally buoyant with respect to each phase by turn, and subsequently its motion was monitored for its multiple trajectories through coiled geometry, via an array of strategically placed scintillation detectors (NaI(TI)). From the “sojourn times” of the tracer Particle through the coiled tube, the characteristic exit age distribution (E(t)) and occurrence density distribution were obtained. The former information has related to the velocity field of either phase (RPT-TOF), while the latter information has related to the volume fraction field of either phase (RPT-VOF). Further analysis of this data has revealed interesting features, such as the onset of phase inversion and the distinction of flow regimes.

  • on the experimental investigation of gas liquid flow in bubble columns using ultrafast x ray tomography and Radioactive Particle tracking
    Chemical Engineering Science, 2017
    Co-Authors: Salar Azizi, Shantanu Roy, Ashutosh Yadav, Yuk Man Lau, Uwe Hampel, Markus Schubert
    Abstract:

    Abstract Several techniques have been developed in the past to measure gas and liquid phase dynamics; however, reported data were mostly gathered individually for either liquid velocity, or volume fraction (phase holdup), but never when both are measured in the same system. In this work, arguably for the first time, bubble column hydrodynamics have been investigated using two complementary advanced non-invasive measurement techniques, namely Ultrafast X-ray Computed Tomography (UXCT) and Radioactive Particle Tracking (RPT). The UXCT experimental data in terms of gas phase structure is used in a supportive way to explain the liquid velocity profiles of the RPT data. Results of both experimental techniques are verified in a complementary manner using the mass conservation calculation. The results show good agreement. It is envisioned that the presented data would be helpful in the development and validation of numerical models for better predicting the flow profiles in bubble columns.

  • comparative analysis of liquid hydrodynamics in a co current flow through bubble column with densely packed internals via radiotracing and Radioactive Particle tracking rpt
    Chemical Engineering Science, 2017
    Co-Authors: Dinesh V Kalaga, Sunil Goswami, H J Pant, Sameer V Dalvi, J B Joshi, Ashutosh Yadav, Vishal H Bhusare, Shantanu Roy
    Abstract:

    Abstract Bubble column reactors are widely used for gas-liquid operations and most often are fitted with vertical internals for appropriate heat transfer. Apart from these applications, cylindrical vessels with concentrically installed vertical tube bundles find major use in boiling water reactors. Most often, heat removal takes place in boiling water reactors by phase change of the flowing water, which results in a complex, axially developing and highly dynamic two-phase flow pattern. Though the hydrodynamics in a bubble column with vertical internals have been addressed in few publications, the characteristics of liquid phase mixing and turbulence over a wide range of operating conditions and dense configuration of the internals have not been reported thus far. The present communication addresses the hydrodynamic characteristics in bubble column equipped with dense internals over a wide range of superficial gas and liquid velocities. Experiments were performed using the air-water system in a 120 mm I.D. bubble column with, and without internals, by varying the percent cross-sectional area covered by the internals. A non-invasive Radioactive Particle Tracking (RPT) method has been employed for estimating the hydrodynamic parameters and mixing characteristics have also been investigated using residence time distribution (RTD) studies with radiotracers. The experimental results obtained in this work indicates that the configuration of the heat exchanger internals, superficial gas, and liquid velocities have a strong effect on liquid phase hydrodynamics and mixing characteristics.

  • monte carlo real coded genetic algorithm mc rga for Radioactive Particle tracking rpt experimentation
    Aiche Journal, 2017
    Co-Authors: Ashutosh Yadav, H J Pant, Manojkumar Ramteke, Shantanu Roy
    Abstract:

    Radioactive Particle tracking (RPT) technique is a non-invasive velocimetry technique, extensively applied to study hydrodynamics of dense multiphase systems. In this technique, the position of a Radioactive tracer Particle, designed to mimic the phase of interest, is followed as a Lagrangian marker of point velocity. Computational limitations encountered during tracer Particle position reconstruction (which is an inherently slow process) have thus far restricted the use of this versatile technique only to small-scale process vessels. Here, we present a noteworthy improvement over the classical Monte Carlo (MC) algorithm for tracer Particle position reconstruction, whereby we enhance the convergence and computational speed of the algorithm using Real Coded Genetic Algorithm (RGA) optimization. This modification results in drastic reduction in computational time required for detector parameter estimation, and altogether eliminates the need for the “distance-count map,” which was earlier inherent to RPT experimentation. This article is protected by copyright. All rights reserved.

Milorad P. Dudukovic - One of the best experts on this subject based on the ideXlab platform.

  • gas liquid flow generated by a rushton turbine in stirred vessel carpt ct measurements and cfd simulations
    Chemical Engineering Science, 2005
    Co-Authors: Avinash R. Khopkar, Aravind Rammohan, Vivek V. Ranade, Milorad P. Dudukovic
    Abstract:

    In this work, computer-automated Radioactive Particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid stirred vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation time distribution in a vessel. A two-fluid model along with the standard k-e turbulence model was used to simulate the dispersed gas-liquid flow in a stirred vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial stirred vessels.

  • quantification of solids flow in a gas solid riser single Radioactive Particle tracking
    Chemical Engineering Science, 2004
    Co-Authors: Satish Bhusarapu, Muthanna H Aldahhan, Milorad P. Dudukovic
    Abstract:

    Solids in risers of circulating fluidized beds (CFB) exhibit local backflow and recirculation. Measurement of the concentration-time response to an impulse injection of tracer, even at two elevations cannot determine the residence time distribution (RTD) of solids uniquely. Hence, evaluation of RTD in risers from conventional tracer responses is difficult and often not possible. In addition, estimating the solids circulation rate in these closed loop systems, is a non-trivial problem. In this work, a single Radioactive Particle in the CFB loop is tracked during its multiple visits to the riser and, by invoking ergodicity, solids circulation rate, accurate solids RTD and additional information on the solids flow pattern in the riser are estimated. A calibration curve was established for the overall solids mass flux as a function of superficial gas velocity. A second peak in the probability density function (PDF) of the solids RTD curve in the riser was observed for operating conditions in the fast-fluidization regime.

  • Application of wavelet filtering to the Radioactive Particle tracking technique
    Flow Measurement and Instrumentation, 2002
    Co-Authors: Sujatha Degaleesan, Milorad P. Dudukovic, Y. Pan
    Abstract:

    Abstract The Computer Automated Radioactive Particle Tracking (CARPT) technique has been used for the investigation of fluid dynamics, material dispersion and mixing in various multiphase rectors. The accuracy of the CARPT measurement depends on the properties of the tracer Particle, the algorithm and the technique for calibration and signal processing. In this paper, a filtering technique based on the wavelet theory for the removal of white noise from the data is presented. It is shown, experimentally, that the adopted wavelet-based filtering algorithm reduces the level of noise in the data by 80–90%. The suitability and necessity of wavelet filtering are further illustrated by performing a group of typical CARPT experiments in an air-water bubble column operated at different superficial gas velocities. It is demonstrated that the use of the unfiltered data results in significant over-estimation of turbulent parameters while the influences on the mean velocities are minor.

  • Optimal design of Radioactive Particle tracking experiments for flow mapping in opaque multiphase reactors.
    Applied radiation and isotopes : including data instrumentation and methods for use in agriculture industry and medicine, 2002
    Co-Authors: Shantanu Roy, Faïçal Larachi, Muthanna H. Al-dahhan, Milorad P. Dudukovic
    Abstract:

    In the past decade, Radioactive Particle tracking techniques have emerged in the field of chemical engineering and have become increasingly popular for non-invasive flow mapping of the hydrodynamics in multiphase reactors. Based on γ-ray sensitization of an array of scintillation detectors, the Computer Automated Radioactive Particle Tracking (CARPT) technique measures flow fields by monitoring the actual motion path of a single discrete Radioactive flow follower which has the physical properties of the phase whose motion is being followed. A limitation to the accuracy of CARPT lies in the error associated with the reconstruction of the tracer Particle position which affects the space-resolution capability of the technique. It is of interest, therefore, to minimize this error by choosing wisely the best hardware and an optimal configuration of CARPT detectors’ array. Such choices are currently based on experience, without firm scientific basis. In this paper, through theoretical modeling and simulation, we describe how the accuracy of a Radioactive Particle tracking setup may be assessed a priori. Through an example of a proposed implementation of CARPT on a gas–solids riser, we demonstrate how this knowledge can be used for choosing the hardware required for the experiment. Finally, we show how the optimal arrangement of detectors can be effected for maximum accuracy for a given amount of monetary investment for the experiment.

  • characterization of single phase flows in stirred tanks via computer automated Radioactive Particle tracking carpt
    Chemical Engineering Research & Design, 2001
    Co-Authors: Aravind Rammohan, Muthanna H Aldahhan, A Kemoun, Milorad P. Dudukovic
    Abstract:

    Single phase flows in stirred tanks have been extensively characterized using different experimental techniques like Hot Wire Anemometry1, Laser Doppler Anemometry2, and Digital Particle Imaging Velocimetry3. None of these techniques however, show much promise for the interrogation of opaque multiphase flows. Hence, little or no information of the local fluid dynamics of multiphase flows in stirred tanks is available. Non-optical techniques like Computer Automated Radioactive Particle Tracking (CARPT) and Computed Tomography (CT) have been successfully applied to probe a variety of multiphase reactors4–5 such as bubble columns6–7, risers8 etc., over a range of dispersed phase holdups. CARPT provides the local fluid dynamic information such as velocities and the turbulence parameters throughout the system that is investigated. CT provides time averaged local dispersed phase holdup profiles in various planes of the entire reactor. In this study, it is proposed to extend these techniques to characterize gas-liquid flows in stirred tank reactors. As a first step, CARPT is implemented in characterization of single phase flows in stirred tanks. CARPT experiments have been performed with water at 150 rpm in a 0.20m cylindrical tank quipped with a six bladed Rushton turbine (0.067m dia) conforming to the standard Holland and Chapman9 configuration. The CARPT technique is shown to capture some of the important flow phenomena observed in such flows, like the two recirculating loops above and below the impeller and the dead zones at the bottom of the tank. Radial pumping numbers determined by CARPT (0.67 near the impeller tip) compare reasonably well with data reported in the literature. Comparison of the complete three dimensional mean velocity profiles from CARPT with similar PIV, LDA and other data reported in the literature reveals that CARPT captures the right order of magnitude of the radial and the tangential velocities. Comparisons of the fluctuating velocity components, like the root mean squared (rms) velocity and the turbulent kinetic energy, suggest that the CARPT experiments were limited by large tracer Particle size (dp = 2.3 mm) from sampling the high frequency fluctuations of the fluid. In addition, the three dimensional profiles of the components of the Reynolds stress tensor are measured. The detailed comparisons, even with the large tracer Particle, indicate that CARPT measurements capture all the important qualitative features of the flow and quantitatively capture the right order of magnitude of the mean flow parameters. The quantitative comparisons suggest that the current size of the tracer Particle restricts it from responding completely to the fluid phase fluctuations. Some Lagrangian measures of the fluid dynamics like the ‘Sojourn’ time distributions (STDs) in different zones of the reactor, Circulation Time Distributions (CTDs), Particle Return Maps to specific planes, Poincarre sections and Hurst exponents are evaluated from the collected CARPT data.