bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐sustained oscillations in opposed impinging jets in an enclosure
Authors: Johnson David A. , Wood Philip E. 
Published: May 2010

AbstractThe flow of jets in confining enclosures has significant application in many engineering processes. In particular, the impingement of axisymmetric jets in a confined space has been examined using flow visualization, laser Doppler anemometry, and numerical simulations. Several flow regions were found; stable steady, regular oscillatory, and irregular oscillatory. Initially, a steady flow field existed for all arrangements for Red < ˜90 (based on the nozzle diameter d, the fluid kinematic viscosity v and the volumetric flow rate Q through the nozzle (Q = πd2/4Uavg)) but subsequent increments in the fluid velocity caused a regularly oscillating flow field to emerge. The onset of the oscillations and the upper limit of finite oscillations were found to be a function of the Red, and the nozzle diameter to chamber dimension ratio. Steady numerical simulations predicted the steady flow field well and good agreement was obtained in unsteady simulations of the oscillating flow field. The oscillating flow field is considered to be a class of self‐sustaining oscillations where instabilities in the jet shear layer are amplified because of feed back from pressure disturbances in the impingement region.
Instabilities when using a standard (T/3) rushton turbine for stirring as foam disruption (SAFD)
Authors: Boon Lotte A. , Bujalski Waldemar , Nienow Alvin W. , Hoeks Frans W.J.M.M. , Van Der Lans Rob G.J.M. 
Published: May 2010

AbstractThe concept of using the upper stirrer for foam disruption in a bioreactor agitated by multiple impellers has recently been published by Hoeks et al. (1997). This concept, stirring as foam disruption (SAFD), was shown by them to be effective with a range of impellers. However, the commonly used (so‐called) standard Rushton turbine of one‐third the fermenter diameter was not included. This paper fills that important gap. By measuring the foam height, the holdup, the power draw and the velocities of the liquid in the dispersion just below its top surface, it is concluded that the SAFD concept does not work well with the standard Rushton turbine. This is because the amount of broth for which foam can be disrupted is less than that found with all the other impellers tested to date; and even when foam disruption occurs, significant flow instabilities and torque fluctuations are found. Perhaps the poor performance of this impeller, which has been used so frequently in industry and in academic studies, explains why the concept of SAFD was not developed earlier.
Development of a novel non‐contact proximity gauge for thickness measurement of soft deposits and its application in fouling studies
Authors: Tuladhar T. R. , Paterson W. R. , Macleod N. , Wilson D. I. 
Published: May 2010

AbstractThis paper describes the development of a novel proximity gauging technique for soft deposits, exploiting a siphon effect. This non‐contact technique has the capability to measure the thickness of soft deposits on a surface in situ and in real time. A theoretical model of performance has been developed and its validity demonstrated by calibration experiments. Local thickness measurements of soft deposits such as whey protein deposit, supermarket butter and sticky foam on metal surfaces had an accuracy of ±20 μm for a deposit thickness of 500 to 1000 μm. The potential of this technique for on‐line monitoring of fouling and cleaning processes in liquid environments is demonstrated by preliminary studies of alkali (NaOH) cleaning of whey protein deposits from stainless steel surfaces.
Influence des principaux paramètres opératoires sur le dépôt de silicium à partir de silane par CVD en lit fluidisé en vue de limiter les problèmes d'agglomération
Authors: Ramiro Ruvalcaba J. Rodriguez , Caussat Brigitte , Hemati Merhdji , Couderc Jean‐Pierre 
Published: May 2010

AbstractLe dépôt CVD de silicium à partir de silane sur des poudres d'un lit fluidisé constitue une technique de modification de surface efficace et flexible, qui présente cependant l'inconvénient majeur de voir la couche de particules s'agglomérer au‐delà d'une certaine concentration d'entrée en réactif. C'est pour progresser dans la compréhension de ce phénomène que des conditions opératoires jusqu'alors peu explorées, couvrant des températures inférieures à 550°C, ont été étudiées à la fois expérimentalement et par voie théorique, à l'aide de modèles globaux de simulation de type Kato et Wen. L'influence des principaux paramètres opératoires a été analysée en détail, non seulement sur le plan de l'efficacité globale du procédé, mais aussi en ce qui concerne le comportement thermique du lit fluidisé, directement lié aux mouvements des particules solides, et done à I'éventuelle prise en masse de la couche.
Simulation of fine particle formation by precipitation using computational fluid dynamics
Authors: Piton Damien , Fox Rodney O. , Marcant Bruno 
Published: May 2010

AbstractThe 4‐environment generalized micromixing (4‐EGM) model is applied to describe turbulent mixing and precipitation of barium sulfate in a tubular reactor. The model is implemented in the commercial computational fluid dynamics (CFD) software Fluent. The CFD code is first used to solve for the hydrodynamic fields (velocity, turbulence kinetic energy, turbulent energy dissipation). The species concentrations and moments of the crystal size distribution (CSD) are then computed using user‐defined transport equations. CFD simulations are performed for the tubular reactor used in an earlier experimental study of barium sulfate precipitation. The 4‐EGM CFD results are shown to compare favourably to CFD results found using the presumed beta PDF model. The latter has previously been shown to yield good agreement with experimental data for the mean crystal size at the outlet of the tubular reactor.
Gas flow regime changes in a bubble column filled with a fibre suspension
Authors: Heindel Theodore J. 
Published: May 2010

AbstractGas flow characteristics in opaque fibre suspensions have been captured on film using a stop‐motion X‐ray imaging technique called flash X‐ray radiography (FXR). Gas flows in a bubble column filled with various cellulose fibre suspensions from 0% (an air–water system) to 5% by mass have been observed. The gas flow regime changes from vortical to churn‐turbulent as the fibre concentration increases for a fixed superficial gas velocity. Two new gas flow regimes, identified as surge churn‐turbulent and discrete channel flow, have also been recorded at high fibre concentrations.
Radial nonuniformity index (RNI) in fluidized beds and other multiphase flow systems
Authors: Zhu Jing‐Xu (Jesse) , Manyele Samwel V. 
Published: May 2010

AbstractThe radial nonuniformity index (RNI) is a new non‐dimensional index recently devised to quantify the extent of radial variations of flow parameters in fluidized beds and other multiphase flow systems. The index, defined as the ratio of the standard deviation of the given flow parameter in the radial direction to the maximum practically possible standard deviation of that particular parameter, is shown to be an excellent measure of the radial flow structure. This index allows the use of a single value to summarize the radial variation of a given flow parameter. The higher the value of the RNI the less uniform is the flow, and vice versa. Using this technique, radial distributions of local solids concentration and particle velocities from different circulating fluidized bed systems (gas‐solid and liquid‐solid, upflow and downflow) were examined. It has been found that the RNI can be confidently related to the flow conditions in the circulating fluidized beds, and more insight understanding has been achieved.
Application of an air‐operated two impinging streams extractor in liquid‐liquid extraction and comparison with other contactor types
Authors: Dehkordi Asghar Molaei , Kaghazchi Tahereh , Sohrabi Morteza 
Published: May 2010

AbstractExtraction of succinic acid by means of normal butanol from its aqueous solutions (BSW), acetic acid by means of distilled water from kerosene (WAK) and iodine by means of kerosene from its aqueous solution (KIW) have been investigated in an air‐operated two impinging streams extractor (AOTISE) with spray nozzles. The effects of air flow rate, solutions flow rate, extractor length and diameter as well as modes of operation and impinging streams on extraction efficiency have been investigated. These results indicate that AOTISE is an efficient device for extraction processes. In addition, the overall volumetric mass transfer coefficients (KLa) are reported. The latter coefficients are important in design and may be used to compare the performance capability of various kinds of extractors.
CO2N2 and CO2CH4 binary adsorption isotherms with H‐ZSM5: The importance of experimental data regression with the concentration pulse method
Authors: Harlick Peter J. E. , Tezel F. Handan 
Published: May 2010

AbstractA novel functional form for describing the binary Kp data obtained with concentration pulse chromatography has been developed. The application of the novel function set was evaluated by studying the binary CO2‐CH4 and CO2‐N2 systems using H‐ZSM‐5 as the adsorbent with SiO2/Al2O3 ratios of 30 and 280. Pure isotherms at 40°C, up to 100 kPa pressure and binary isotherms at 40°C and 100 kPa total pressure have been determined using the concentration pulse method. The results from the use of the novel function set show that a small deviation of the regression curve from the experimental data will result with differences in the binary isotherms.
Extended kalman filter‐based nonlinear model predictive control of a continuous KCl‐NaCl crystallizer
Authors: Tadayyon Abdulsamad , Rohani Sohrab 
Published: May 2010

AbstractAn extended Kalman filter (EKF)‐based nonlinear quadratic dynamic matrix control (EQDMC) for an evaporative cooling draft‐tube baffled (DTB) KCl crystallizer is developed. The controller is used to maintain the productivity, crystal mean size and impurity of crystals. Since these controlled variables are not directly measurable, the EKF is used to estimate them. The nonlinear controller is a combination of an extended linear dynamic matrix control (EDMC) and the quadratic dynamic matrix control (QDMC). This combination provided good control of the system despite the process nonlinearity, constraints, and inadequate reliable online measurement of the controlled variables. The performance of the controller in the presence of plant/model mismatch, disturbance, wrong estimation and simultaneous step changes in the controller setpoints is discussed.
Fuzzy multi‐model based adaptive predictive control and its application to thermoplastic injection molding
Authors: Li Mingzhong , Yang Yi , Gao Furong , Wang Fuli 
Published: May 2010

AbstractMany chemical processes are inherently nonlinear. A single linear model is ineffective for these processes. Several local linear models may be developed for different operating conditions. A combination of these local models, through a fuzzy logic representation, results in an overall model for a wider operation range. In this paper, on‐line improvements and a fuzzy multi‐model have been proposed for predictive control implementation. Firstly, assuming that the premises of the fuzzy rules keep their original structures, the linear parameters in the rule consequents are on‐line updated by a weighted recursive least squares algorithm at each sample interval. Secondly, a batch learning algorithm is proposed to tune the fuzzy rule premises using a competitive learning algorithm. The effectiveness of the proposed improvements is demonstrated with experimental applications to the filling velocity control of thermoplastic injection molding
Dynamic simulation and control of a paper machine wet end
Authors: Yap Eddy F. , Kwok K. Ezra , Dumont Guy A. 
Published: May 2010

AbstractA good simulation model for paper machines can be used to identify deficiencies in the design, bottlenecks during operation, and regions of poor control. It also allows users to test their hypotheses and innovations without potentially causing major upsets and reducing throughput. In this work, a dynamic model of the wet end system has been developed using the IDEASTM platform, describing the distribution of fines, fillers and fibres throughout the system. The model was then tested at steady state with mill data for the low‐ash and high‐ash production grades, and the results show that over 70% of the predicted values had only 5% deviation. The dynamic simulation was also used to show that the retention aid controller would react in the wrong direction due to changes in the wire pit consistency and the stock ratio would cause major changes in stream compositions and consistencies of the wet end.
Cold and hot gas filtration using a novel mobile granular bed with an inner fluidized section
Authors: Abatzoglou Nicolas , Gagnon Martin , Chornet Esteban 
Published: May 2010

AbstractTwo experimental studies were conducted with a novel moving granular bed filter (NMGBF). The first one was performed on a cold and dry mock‐up module operated at room temperature and was aimed at a) proving the concept, b) establishing the operating patterns and flow profiles and c) optimizing the operating conditions. The gas flowrate and the geometry of the filter were the main variables studied. The second study was conducted on a prototype hot filter PDU (Process Development Unit) under real time operating conditions. The filter was one of the modules of a hot‐gas‐conditioning‐train in a fluidized bed gasifier. Results showed similar particles collection efficiency for hot‐ and cold‐dry filtration. The filter showed an efficiency of 99.9% over 55 h filtration time for particles larger than 1 μm, while for submicronic particles the efficiency is between 84% and 96% (weight basis). This paper presents and discusses the apparatus, the experimental methods and conditions as well as characteristic results on the two prototypes used.
γ‐Alumina supported Cu‐Ni bimetallic catalysts: Characterization and selective hydrogenation of 1,3‐butadiene
Authors: Kang Min , Song Min Woo , Kim Tae Won , Kim Kyung Lim 
Published: May 2010

AbstractAddition of a second metal often improves the selectivity of a supported catalyst for the hydrogenation of 1,3‐butadiene. Catalysts containing 15 wt% Ni and varying amounts of Cu were prepared and characterized by TPR, XRD and XPS. The Cu‐Ni interaction affects the reduction behavior of the catalysts. TPR result shows that the synergetic effect of copper and nickel modifies the capability of metal to combine with hydrogen in bulk phase. The Ni 2p spectra in XPS shows significant shifts toward lower binding energies with increasing copper loading. From XRD results it is represented that aggregation of nickel occurs more easily due to the copper addition. The adding of copper on Ni/Al2O3 makes the conversion rate decreased and increases the selectivity to 1‐butene.
A catalyst deposited over the external surface of the reactor tubes—A new solution for carrying out heterogeneous catalytic processes
Authors: Anastasov Asen I. , Nikolov Valentin A. 
Published: May 2010

AbstractA mathematical model of a new reactor design has been proposed. In the new reactor the catalyst is deposited over the external surface of the tubes, where the coolant flows. The widespread industrial process of oxidation of o‐xylene into phthalic anhydride was investigated. The results obtained show significant advantages of the new design in comparison with the conventional fixed bed reactor operating in the industry. They are: much higher productivity, easily controlled temperature regime, raised selectivity and decrease content of side products, as well as an opportunity for additional feed‐in of the reagent along the reactor height. The technological regime of the oxidation process was optimized.
Modelling and economic analysis of gas production from hydrates by depressurization method
Authors: Khataniar Santanu , Kamath Vidyadhar A. , Omenihu Sunday D. , Patil Shirish L. , Dandekar Abhijit Y. 
Published: May 2010

AbstractGas production from a hydrate reservoir involves decomposition of the solid hydrate. An analytical model is developed to predict reservoir performance for gas production by the depressurization method from a hydrate reservoir containing associated free gas. The model is developed by combining the intrinsic kinetics of hydrate decomposition, which is of interest to chemical engineers, with gas inflow performance relationship and material balance equations. An economic analysis model is also developed and incorporated with the reservoir performance model. These models are used in a case study of gas production from a hydrate reservoir in the Alaskan North Slope. The results show that gas transportation cost is the main factor controlling feasibility of commercial gas production. The hydrate zone contributes significantly to overall reservoir performance by arresting pressure decline and maintaining gas production rate.
Perturbation signal design for neural network based identification of multivariable nonlinear systems
Authors: Kulkarni Pankaj S. , Gudi Ravindra D. 
Published: May 2010

AbstractThe paper focuses on issues in experimental design for identification of nonlinear multivariable systems. Perturbation signal design is analyzed for a hybrid model structure consisting of linear and neural network structures. Input signals, designed to minimize the effects of nonlinearities during the linear model identification for the multivariable case, have been proposed and its properties have been theoretically established. The superiority of the proposed perturbation signal and the hybrid model has been demonstrated through extensive cross validations. The utility of the obtained models for control has also been proved through a case study involving MPC of a nonlinear multivariable neutralization plant.
The mixing sensitivity of polysulphide generation
Authors: Dobson Heather K. , Bennington Chad P.J. 
Published: May 2010

AbstractThe effect of mixing and mass transfer on polysulphide generation by catalytic oxidation of sodium sulphide was studied using two batch‐operated reactors. One was a sparged reactor operated at atmospheric pressure and low mixing intensities (0.37 to 28 W/kg), the other was an unsparged pressurized reactor characterized by high mixing intensities (17 to 3100 W/kg). The reaction parameters examined included the impeller speed, sparged gas flowrate, oxygen partial pressure, and catalyst loading and type. In both reactors the maximum polysulphide yield, selectivity and rate of formation increased with increasing energy dissipation. Increased gas sparging increased the rate of reaction, but had little effect on either yield or selectivity. Increased oxygen partial pressure increased the rate of oxidation but decreased both the yield and selectivity. The type of catalyst dramatically affected the yield of polysulphide produced for a given set of reaction conditions with improved mixing increasing reaction rate, yield and selectivity.
Rheological examination of temperature dependence of conventional and polymer‐modified road bitumens
Authors: Zupančič Andreja , Žumer Miha 
Published: May 2010

AbstractRheological characterization of two types of road bitumens, conventional and polymer‐modified, has been examined in the temperature range between 20°C and 140°C. Tests were carried out before and after ageing following a thin‐film oven test. Polymer‐modified bitumens exhibit non‐Newtonian behaviour up to the 120°C due to a complex secondary structure formed by added polymers. For conventional bitumens, Newtonian behaviour was observed above 60°C. Special attention was paid to measurements and to analysis of the dynamic data of oscillatory shear. The mechanical spectra in a wide frequency range have been obtained using the WLF time‐temperature superposition principle. The analysis of viscoelastic data clearly showed the differences between the two types of bitumen. Conventional bitumens were more sensitive to temperature and to the ageing effects. For polymer modified bitumens, the elastic contribution to viscoelastic response was more pronounced, and independent of temperature and ageing.
Bubble coalescence and its effect on dynamic foam stability
Authors: Cho Yoon Seong , Laskowski Janusz S. 
Published: May 2010

AbstractThe size of bubbles generated using a single‐hole sparger, a multi‐hole sparger and a flotation cell were measured. While the size of bubbles generated from the single‐hole sparger does not depend on frother concentration, the bubble size strongly depends on frother concentration when the multi‐hole sparges, or flotation cell, are utilized. The bubbles size ceases to depend on frother at the concentrations exceeding the value characteristic for each frother and referred to as the critical coalescence (CCC). All the bubble size vs. frother concentration curves converge on a single curve. Aqueous solutions of the frothers that are characterized by low CCC values from foams quite stable under dynamic conditions. Since bubble coalescence can be inhibited by frother concentrations exceeding the CCC, sparing systems can be studied and compared only at frother concentrations that exceed CCC.
Flow regimes in a turbulent bed contactor
Authors: Albert Bruce E.R. , Pillutla Sai S.T. , Kamatam Krishnaiah 
Published: May 2010

AbstractExperiments were conducted in a turbulent bed contactor (TBC) with and without downcomer operating in Type I and Type II modes to obtain the flow regime maps. The variables include flow rate of the gas and liquid phases, size and density of the particles, bed height, free open area of the supporting grid, and diameter and weir height of the downcomer. Static, partially fluidized, completely fluidized, flooding and annular regimes are identified depending on geometric and operating conditions. The effect of these variables on flow maps is discussed and correlations are proposed for delineating the flow regimes.
Pressure buildup in gas‐liquid flow through packed beds due to deposition of fine particles
Authors: Gray Murray R. , Srinivasan Naras , Masliyah Jacob H. 
Published: May 2010

AbstractIn order to understand the increase in pressure drop in hydrotreating reactors due to deposition of fine solids, experiments were conducted with a model suspension of kaolin clay in kerosene. The suspension was circulated through packed beds of catalyst pellets in the trickle‐flow and pulse‐flow regimes, and the increase in pressure drop measured as a function of particle concentration in the bed. The increase in pressure drop was linear with particle concentrations over the range 0–60 kg.m−3. A consistent approach to modeling the pressure drop behavior was to determine an effective porosity of the packed bed as a function of the concentration of fine particles, then use this porosity in the Ergun equation as a basis for calculating the two‐phase pressure drop.
Free convective mass transfer at horizontal single screens and arrays of horizontal screens in relation to electrochemical reactor design
Authors: Sedahmed Gomma H. , Nirdosh Inder 
Published: May 2010

AbstractRates of free convection mass transfer at horizontal screens made of woven cylindrical wires were studied by measuring the limiting current of copper deposition from acidified copper sulphate solutions for a horizontal screen surrounded by a cylindrical counter‐electrode. Variables studied were screen characteristic parameters and the physical properties of solutions. The data were correlated by a new mass transfer correlation. Mass transfer measurements at arrays of separated horizontal screens revealed that screen spacing has a little effect on the rate of array mass transfer. On the other hand, increasing the number of screens per array was found to decrease the rate of array mass transfer. Implications of the present results for the design and operation of electrochemical reactors suitable for heavy metal removal from waste water and electrosynthesis are noted.