The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Szymon Woziwodzki - One of the best experts on this subject based on the ideXlab platform.

  • Gas-Liquid Mixing in an Unbaffled Vessel with a Forward-Reverse Rotating Scaba Impeller
    Practical Aspects of Chemical Engineering, 2020
    Co-Authors: Sebastian Frankiewicz, Szymon Woziwodzki
    Abstract:

    Mixing is one of the most important unit operations carried out in the chemical, food and related industries. It is still in the research of many scientists because of its high energy consumption. Unsteady Mixing with an emphasis on its use in gas-liquid systems is presented. In such a Mixing there is no need to use baffles e.g. in the food and pharmaceutical industries. In brewing, even with steady Mixing, baffles are not used because it makes the washing process too difficult and affects its frequency. An experiment was conducted for the Scaba 6SRGT to compare the unsteady and steady Mixing Power in both a single-phase and a two-phase gas-liquid system. One would like to achieve an improvement in Mixing Power through the use of forward-reverse Mixing. Different oscillation frequencies are used for unsteady Mixing using a triangular time-course of impeller speed. Using forward-reverse Mixing in a single-phase system has caused an increase in Mixing Power by about 80%. For forward-reverse Mixing in the gas-liquid system, lower RPD values are observed compared to steady Mixing, which shows greater Power decreases caused by gas introduction.

  • Application of Morison Equation in Unsteady Mixing Characteristics
    Practical Aspects of Chemical Engineering, 2020
    Co-Authors: Szymon Woziwodzki
    Abstract:

    Unsteady Mixing is one of the methods increasing Mixing intensity, especially in an unbaffled stirred vessel. However, because of the unsteady motion of the impeller, it is difficult to describe it. One of the most important Mixing parameters is Mixing Power. It is not constant and depends on the Reynolds number than well as the oscillation frequency. Therefore, knowledge about forces acting on an impeller is essential. In marine engineering and fluid dynamics, the Morison equation is commonly used to describe wave forces acting on offshore structures. In this way, the motion of waves is considered as sinusoidal unsteady flow. Therefore, the Morison equation could describe forces acting on a rotating impeller, however, it requires consideration of all forces, beside drag and inertia force, acting in a stirred vessel.

  • Effect of Blade Shape on Unsteady Mixing of Gas-Liquid Systems
    Lecture Notes on Multidisciplinary Industrial Engineering, 2018
    Co-Authors: Sebastian Frankiewicz, Szymon Woziwodzki
    Abstract:

    Mechanical Mixing can be conducted in few ways. One is unsteady Mixing which is used in all cases where it is not recommended to use baffles. In this Mixing, the impeller speed is variable over time which causes a higher Mixing Power demand as compared to steady Mixing. In unsteady Mixing, also a higher stress around the impeller can be observed as well as the increased axial force in the stirred vessel which results in lower minimum impeller speed in solid-liquid systems. Thus, Mixing can be also used in gas-liquid systems allowing to generate a higher relative Power demand in relation to the steady Mixing as well as higher mass transfer coefficients. Its value, just as for steady Mixing, is affected by impeller’s geometry. This chapter analyzes how the shape of impeller’s blade affects the steady and unsteady Mixing for impellers with elliptical and hollow unsymmetrical blades. In addition, basic equations describing the torque and impeller speed variations over time are presented together with the maximum and average Mixing Power equations.

  • Turbulent forward-reverse Mixing characteristics in vessel with multiple-turbine impellers
    Journal of Chemical Technology & Biotechnology, 2012
    Co-Authors: Szymon Woziwodzki
    Abstract:

    BACKGROUND: Mixing in unbaffled vessel with multiple-turbine impellers was studied. The Mixing time and Mixing Power were evaluated in relation to the distance between impellers and the number of impellers. RESULTS: It has been confirmed that frequency of oscillation has no influence on the Mixing time and Mixing Power values or on drag and added mass coefficients. The coefficients were greater when distance between impellers was smaller. Moreover added mass coefficient was dependent on Reynolds number (ni > 2). Compared with unidirectional Mixing conditions, for systems with one type of impeller, the Power requirement was about 38% higher for forward-reverse Mixing. Despite the fact that the Power demand was greater, the Mixing time was not shorter, but about 30% higher than unidirectional Mixing in a baffled vessel. However, the forward-reverse Mixing mode exhibits a higher level of homogeneity which it achieved faster than unidirectional Mixing. CONCLUSION: The Power requirements and Mixing time for forward-reverse Mixing mode were higher in comparison with unidirectional Mixing. Despite this, higher values of homogeneity were achieved faster. Higher levels of shear rate and better homogeneity indicate that forward-reverse Mixing can be beneficial for multi-phase Mixing in vessels with multiple impellers. © 2012 Society of Chemical Industry

  • Unsteady Mixing Characteristics in a Vessel with Forward-Reverse Rotating Impeller
    Chemical Engineering & Technology, 2011
    Co-Authors: Szymon Woziwodzki
    Abstract:

    Usually, Mixing is carried out in a vessel with four baffles and a single impeller. In some applications, however, the use of a baffled vessel is not recommended. One of the stirring methods used instead is unsteady agitation with forward-reverse rotating impellers. The aim of this work was to characterize the agitation characteristics in a baffled and an unbaffled vessel with a turbine impeller. Mixing time and Mixing Power were evaluated in relation to the presence of baffles and the frequency of forward-reverse rotation. It was found that the frequency of oscillation does not affect either the Mixing time and Mixing Power values or the drag and added mass coefficients. Power requirements and Mixing time were higher compared to the steady Mixing conditions in a baffled vessel. The results showed that it is not recommended to use baffles because they have no influence on unsteady Mixing.

Beatrice Cabon - One of the best experts on this subject based on the ideXlab platform.

  • New optical microwave up-conversion solution in radio-over-fiber networks for 60-GHz wireless applications
    Journal of Lightwave Technology, 2006
    Co-Authors: Yannis Le Guennec, Gisele Maury, Jianping Yao, Beatrice Cabon
    Abstract:

    A new method for generating optical microwave Mixing based on the optical phase modulation and the fiber chromatic dispersion is further investigated. A theoretical approach based on the analysis of the optical field spectrum has lead to the evaluation of the Mixing Power and optimal fiber lengths of 60-GHz radio-over-fiber (RoF) networks. Results have shown adaptable fiber lengths to match the network specifications.

  • Improvement of dispersion resistance in analog radio-on-fiber upconversion links
    Journal of Lightwave Technology, 2003
    Co-Authors: Yannis Le Guennec, Gisele Maury, Beatrice Cabon
    Abstract:

    Dispersion fiber sensitivity in optical microwave upconversion links is investigated. Simulations are carried out to calculate output optical spectra and to evaluate Mixing Power as a function of fiber length for different upconversion systems using dual drive/standard Mach-Zehnder modulators or an unbalanced Mach-Zehnder interferometer (UMZ). The latter solution prevents complete cancellation of Mixing Power because of the asymmetric double sideband optical spectrum detected at the output of the UMZ. It is shown that an optimum value of the linewidth enhancement factor of the laser diode can be found to minimize degradations of the Mixing Power along the fiber.

  • Improvement of dispersion resistance in analog radio-on-fiber upconversion links
    MWP 2003 Proceedings. International Topical Meeting on Microwave Photonics 2003., 2003
    Co-Authors: Yannis Le Guennec, Gisele Maury, Beatrice Cabon, L. Bastard
    Abstract:

    Simulations and measurements are carried out to evaluate dispersion resistance of up-conversion systems using one-electrode/push-pull Mach-Zehnder modulators or a passive unbalanced interferometer. This former solution causes very low fluctuations for Mixing Power as a function of fiber length.

Bogdan Cazacliu - One of the best experts on this subject based on the ideXlab platform.

  • In-mixer measurements for describing mixture evolution during concrete Mixing
    Chemical Engineering Research & Design, 2008
    Co-Authors: Bogdan Cazacliu
    Abstract:

    Abstract Concrete Mixing experiments have been carried out at an industrial batching plant during a typical production day. 34 batches were tested, including a number of water-to-powder mass ratios, paste contents and mixer filling ratios. Three “in-mixer” measurements yield critical information about mixture composition: Mixing Power, Orbiter – a revolving microwave sensor, and Viscoprobe™ – a drag force measurement on a ball-shaped probe moving through the mixture. A model of the microstructural state evolution in concrete components vs. Mixing time is proposed herein. The transient mixture states are associated with different Power dissipation levels (frictional, cohesive or viscous) and apparent density characteristics. It will be shown that the three sensors are also able to indicate the evolution of mixture state during Mixing, thus facilitating comprehension of sensor signal variations during the Mixing cycle. In addition, a method is devised to improve sensor measurement of the water-to-powder ratio by up to three times. More specifically, the precision of the measured water-to-powder mass ratio is 0.0035, 0.0042 and 0.0051 using the Viscoprobe™, Orbiter and Mixing Power techniques, respectively. The typical water-to-powder mass ratio values for concrete range between 0.4 and 0.6.

  • characterization of the granular to fluid state process during Mixing by Power evolution in a planetary concrete mixer
    Chemical Engineering Science, 2008
    Co-Authors: Bogdan Cazacliu, Jack Legrand
    Abstract:

    Abstract Adding product into the mixer exerts a strong and rapid impact during concrete Mixing. Experimental data obtained from a planetary mixer in a full-scale concrete plant under laboratory conditions show that the state of mixture progress with Mixing time is well described by the Mixing Power evolution. More specifically, a reliable method for detecting the time corresponding to the transformation of a mixture from a cohesive granular material into a granular paste (i.e. the so-called “transition time”), through use of a Mixing Power measurement, will be presented herein. Moreover, once this transition has been achieved, Mixing Power consumption will be related to mixture rheology and then to mixer geometry by means of a simplified hypothesis. This equation can also be obtained via a dimensionless analysis. Lastly, it will be shown that mixture behavior beyond the transition point is well fitted by a hyperbolic equation. The corresponding Mixing Power evolution can then be predicted by the level of Power at this transition time. These results are suitable for application to online process monitoring.

  • Characterizationofthegranular-to-fluidstateprocessduringMixingbyPower evolutioninaplanetaryconcretemixer
    2008
    Co-Authors: Bogdan Cazacliu, Jack Legrand
    Abstract:

    Adding product into the mixer exerts a strong and rapid impact during concrete Mixing. Experimental data obtained from a planetary mixer in a full-scale concrete plant under laboratory conditions show that the state of mixture progress with Mixing time is well described by the Mixing Power evolution. More specifically, a reliable method for detecting the time corresponding to the transformation of a mixture from a cohesive granular material into a granular paste (i.e. the so-called “transition time”), through use of a Mixing Power measurement, will be presented herein. Moreover, once this transition has been achieved, Mixing Power consumption will be related to mixture rheology and then to mixer geometry by means of a simplified hypothesis. This equation can also be obtained via a dimensionless analysis. Lastly, it will be shown that mixture behavior beyond the transition point is well fitted by a hyperbolic equation. The corresponding Mixing Power evolution can then be predicted by the level of Power at this transition time. These results are suitable for application to online process monitoring.

  • In-mixer measurements to describe the mixture kinetics during concrete Mixing
    Chemical Engineering Research and Design, 2008
    Co-Authors: Bogdan Cazacliu
    Abstract:

    Concrete Mixing experiments have been carried out at an industrial batching plant during a typical production day. 34 batches were tested, including a number of water-to-powder mass ratios, paste contents and mixer filling ratios. Three 'in-mixer' measurements yield critical information about mixture composition: Mixing Power, Orbiter - a revolving microwave sensor, and ViscoprobeTM - a drag force measurement on a ball-shaped probe moving through the mixture. A model of the microstructural state evolution in concrete components vs. Mixing time is proposed herein. The transient mixture states are associated with different Power dissipation levels (frictional, cohesive or viscous) and apparent density characteristics. It will be shown that the three sensors are also able to indicate the evolution of mixture state during Mixing, thus facilitating comprehension of sensor signal variations during the Mixing cycle. In addition, a method is devised to improve sensor measurement of the water-to-powder ratio by up to three times. More specifically, the precision of the measured water-to-powder mass ratio is 0.0035, 0.0042 and 0.0051 using the ViscoprobeTM, Orbiter and Mixing Power techniques, respectively. The typical water-to-powder mass ratio values for concrete range between 0.4 and 0.6.

Jack Legrand - One of the best experts on this subject based on the ideXlab platform.

  • characterization of the granular to fluid state process during Mixing by Power evolution in a planetary concrete mixer
    Chemical Engineering Science, 2008
    Co-Authors: Bogdan Cazacliu, Jack Legrand
    Abstract:

    Abstract Adding product into the mixer exerts a strong and rapid impact during concrete Mixing. Experimental data obtained from a planetary mixer in a full-scale concrete plant under laboratory conditions show that the state of mixture progress with Mixing time is well described by the Mixing Power evolution. More specifically, a reliable method for detecting the time corresponding to the transformation of a mixture from a cohesive granular material into a granular paste (i.e. the so-called “transition time”), through use of a Mixing Power measurement, will be presented herein. Moreover, once this transition has been achieved, Mixing Power consumption will be related to mixture rheology and then to mixer geometry by means of a simplified hypothesis. This equation can also be obtained via a dimensionless analysis. Lastly, it will be shown that mixture behavior beyond the transition point is well fitted by a hyperbolic equation. The corresponding Mixing Power evolution can then be predicted by the level of Power at this transition time. These results are suitable for application to online process monitoring.

  • Characterizationofthegranular-to-fluidstateprocessduringMixingbyPower evolutioninaplanetaryconcretemixer
    2008
    Co-Authors: Bogdan Cazacliu, Jack Legrand
    Abstract:

    Adding product into the mixer exerts a strong and rapid impact during concrete Mixing. Experimental data obtained from a planetary mixer in a full-scale concrete plant under laboratory conditions show that the state of mixture progress with Mixing time is well described by the Mixing Power evolution. More specifically, a reliable method for detecting the time corresponding to the transformation of a mixture from a cohesive granular material into a granular paste (i.e. the so-called “transition time”), through use of a Mixing Power measurement, will be presented herein. Moreover, once this transition has been achieved, Mixing Power consumption will be related to mixture rheology and then to mixer geometry by means of a simplified hypothesis. This equation can also be obtained via a dimensionless analysis. Lastly, it will be shown that mixture behavior beyond the transition point is well fitted by a hyperbolic equation. The corresponding Mixing Power evolution can then be predicted by the level of Power at this transition time. These results are suitable for application to online process monitoring.

J.f. Martins-filho - One of the best experts on this subject based on the ideXlab platform.