The Experts below are selected from a list of 10086 Experts worldwide ranked by ideXlab platform
M. W. Abdulrahman - One of the best experts on this subject based on the ideXlab platform.
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Experimental studies of Gas holdup in a slurry bubble column at high Gas temperature of a helium−water−alumina system
Chemical Engineering Research & Design, 2016Co-Authors: M. W. AbdulrahmanAbstract:Abstract In this paper, overall Gas holdup is investigated experimentally for a helium Gas at 90 °C injected through a slurry of water at 22 °C and alumina solid particles in a slurry bubble column reactor. This work examines the effects of Superficial Gas Velocity, static liquid height, solid particles concentration and solid particle diameter, on the overall Gas holdup of the SBCR. These effects are formulated in forms of empirical equations. From the experimental work, it is found that the overall Gas holdup increases by increasing the Superficial Gas Velocity with a higher rate of increase at lower Superficial Gas Velocity. In addition, the overall Gas holdup decreases by increasing the static liquid height and/or the solid concentration at any given Superficial Gas Velocity. Moreover, at a higher solid concentration, the changing rate of the overall Gas holdup with the Superficial Gas Velocity and/or the solid concentration is lower. Furthermore, it is observed that the effect of the solid particle diameter on overall Gas holdup is negligible.
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CFD simulations of direct contact volumetric heat transfer coefficient in a slurry bubble column at a high Gas temperature of a helium-water-alumina system
Applied Thermal Engineering, 2016Co-Authors: M. W. AbdulrahmanAbstract:In this paper, computational fluid dynamics (CFD) simulations are used to investigate the volumetric heat transfer coefficient in a direct contact heat transfer for a helium-water-alumina slurry bubble column reactor, where helium Gas is injected at 90 °C through a slurry of water at 22 °C and alumina solid particles. This paper studies the effects of Superficial Gas Velocity, static liquid height, and solid particle concentration on the volumetric heat transfer coefficient of the slurry bubble column reactor. In this study, it is assumed that the slurry inside the slurry bubble column is perfectly mixed, and the approach used to model the slurry bubble column by CFD is 2D plane. From the CFD results, it is found that the volumetric heat transfer coefficient increases by increasing the Superficial Gas Velocity and decreases by increasing the static liquid height and/or the solid concentration at any given Superficial Gas Velocity. Also, it is found that the rate of decrease of the volumetric heat transfer coefficient with the solid concentration is approximately the same for different Superficial Gas velocities. The results of CFD simulations were compared with experimental data from previous literature and show that the profiles of the volumetric heat transfer coefficient calculated from CFD models generally under-predict the experimental data. The CFD model correctly predicts the experimental effects of static liquid height and solid concentration on volumetric heat transfer coefficient.
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Experimental studies of Gas holdup in a slurry bubble column at high Gas temperature of a helium-water-alumina system
Chemical Engineering Research and Design, 2016Co-Authors: M. W. AbdulrahmanAbstract:In this paper, overall Gas holdup is investigated experimentally for a helium Gas at 90 °C injected through a slurry of water at 22 °C and alumina solid particles in a slurry bubble column reactor. This work examines the effects of Superficial Gas Velocity, static liquid height, solid particles concentration and solid particle diameter, on the overall Gas holdup of the SBCR. These effects are formulated in forms of empirical equations. From the experimental work, it is found that the overall Gas holdup increases by increasing the Superficial Gas Velocity with a higher rate of increase at lower Superficial Gas Velocity. In addition, the overall Gas holdup decreases by increasing the static liquid height and/or the solid concentration at any given Superficial Gas Velocity. Moreover, at a higher solid concentration, the changing rate of the overall Gas holdup with the Superficial Gas Velocity and/or the solid concentration is lower. Furthermore, it is observed that the effect of the solid particle diameter on overall Gas holdup is negligible.
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Experimental studies of direct contact heat transfer in a slurry bubble column at high Gas temperature of a helium–water–alumina system
Applied Thermal Engineering, 2015Co-Authors: M. W. AbdulrahmanAbstract:Abstract In this paper, the direct contact heat transfer is investigated experimentally for a helium Gas at 90 °C injected through a slurry of water at 22 °C and alumina solid particles in a slurry bubble column reactor. This work examines the effects of Superficial Gas Velocity, static liquid height, solid particles concentration and solid particle size, on the volumetric heat transfer coefficient and slurry temperature of the slurry bubble column reactor. These effects are formulated in forms of empirical equations. From the experimental work, it is found that the volumetric heat transfer coefficient and the slurry temperature increase by increasing the Superficial Gas Velocity with a higher rate of increase at lower Superficial Gas Velocity. In addition, the volumetric heat transfer coefficient and the slurry temperature decrease by increasing the static liquid height and/or the solid concentration at any given Superficial Gas Velocity. Furthermore, it is found that the rate of decrease of the volumetric heat transfer coefficient with the solid concentration is approximately the same for different Superficial Gas velocities, and the decrease of the slurry temperature with the solid concentration is negligible.
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Experimental studies of direct contact heat transfer in a slurry bubble column at high Gas temperature of a helium-water-alumina system
Applied Thermal Engineering, 2015Co-Authors: M. W. AbdulrahmanAbstract:In this paper, the direct contact heat transfer is investigated experimentally for a helium Gas at 90°C injected through a slurry of water at 22°C and alumina solid particles in a slurry bubble column reactor. This work examines the effects of Superficial Gas Velocity, static liquid height, solid particles concentration and solid particle size, on the volumetric heat transfer coefficient and slurry temperature of the slurry bubble column reactor. These effects are formulated in forms of empirical equations. From the experimental work, it is found that the volumetric heat transfer coefficient and the slurry temperature increase by increasing the Superficial Gas Velocity with a higher rate of increase at lower Superficial Gas Velocity. In addition, the volumetric heat transfer coefficient and the slurry temperature decrease by increasing the static liquid height and/or the solid concentration at any given Superficial Gas Velocity. Furthermore, it is found that the rate of decrease of the volumetric heat transfer coefficient with the solid concentration is approximately the same for different Superficial Gas velocities, and the decrease of the slurry temperature with the solid concentration is negligible.
N Niels G Deen - One of the best experts on this subject based on the ideXlab platform.
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effect of Superficial Gas Velocity on the solid temperature distribution in Gas fluidized beds with heat production
Industrial & Engineering Chemistry Research, 2017Co-Authors: Mohammad M Banaei, Jeroen Jegers, Martin Van Sint Annaland, J A M Kuipers, N Niels G DeenAbstract:The hydrodynamics and heat transfer of cylindrical Gas–solid fluidized beds for polyolefin production was investigated with the two-fluid model (TFM) based on the kinetic theory of granular flow (KTGF). It was found that the fluidized bed becomes more isothermal with increasing Superficial Gas Velocity. This is mainly due to the increase of solids circulation and improvement in Gas solid contact. It was also found that the average Nusselt number weakly depends on the Gas Velocity. The TFM results were qualitatively compared with simulation results of computational fluid dynamics combined with the discrete element model (CFD-DEM). The TFM results were in very good agreement with the CFD-DEM outcomes, so the TFM can be a reliable source for further investigations of fluidized beds especially large lab-scale reactors
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effect of Superficial Gas Velocity on the particle temperature distribution in a fluidized bed with heat production
Chemical Engineering Science, 2016Co-Authors: Ziyang Z Li, Van Martin Sint M Annaland, Jam Hans Kuipers, N Niels G DeenAbstract:The heat transfer behavior of particles and Gas in an olefin polymerization fluidized bed was numerically analyzed using an in-house developed 3-D computational fluid dynamics discrete element model (CFD-DEM). First the implementation of the model was verified by comparing simulation results with analytical results. A constant volumetric heat production rate was implemented in the particle energy equation to mimic the heat production due to the polymerization reaction. It was found that the probability density function (PDF) of the particle temperature becomes more homogeneous with increasing Superficial Gas Velocity. Furthermore, instantaneous snapshots of the thermal driving force (the difference between the single particle temperature and bed-average Gas temperature, Tp− ) for different heat production rates provide detailed insight in the particle temperature distribution inside the fluidized bed. The time- and bed-averaged particle convective heat transfer coefficient, which was calculated by Gunn׳s correlation, was found to be independent of the Superficial Gas Velocity. This is explained by the fact that the relative Velocity of Gas and particles in the emulsion phase, where most of the particles and Gas interact, is hardly influenced when increasing the Gas Superficial Velocity. From the spatial distribution of Nusselt number, it becomes apparent that the high heat transfer regions are found in the wake of rising bubbles, whereas low heat transfer rates are found in the clouds of the bubbles.
Raymond Viskanta - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Transient Thickness of Pneumatic Foams - eScholarship
2020Co-Authors: Laurent Pilon, Andrei G. Fedorov, Raymond ViskantaAbstract:This paper presents a simple, experimentally validated approach to analyze the transient formation of a foam layer produced by injecting Gas bubbles in a foaming solution. Based on experimental observations, three different regimes in the transient growth of the foam have been identified as a function of the Superficial Gas Velocity. A model based on the mass conservation equation for the Gas phase in the foam combined with three different models for the average porosity is proposed. It is shown that for practical calculations a constant average porosity equal to 0.82 can be used. The model predictions show very good agreement with experimental data for low Superficial Gas Velocity and provide an upper limit of the foam thickness for intermediate and large Superficial Gas velocities. The paper discusses the physical mechanisms that may occur during the foam formation and the effects of the Superficial Gas Velocity on the foam dynamics. The present analysis speculates several mechanisms for the bursting of the bubbles at the top of the foams and proposes the framework for more fundamental and detailed studies.
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minimum Superficial Gas Velocity for onset of foaming
Chemical Engineering and Processing, 2004Co-Authors: Laurent Pilon, Raymond ViskantaAbstract:This paper is concerned with semi-batch foams generated by injecting Gas bubbles in a vertical column containing a liquid phase at rest. Its aim is to better understand the physical mechanisms responsible for foam formation at the liquid free surface and to predict the Superficial Gas Velocity for onset of foaming. The model for predicting the onset of foaming is derived from the one-dimensional drift-flux model for gravity driven flow in the absence of wall shear. The analysis is based on experimental data reported in the literature and covers a wide range of physico-chemical properties, bubble sizes and shapes, and flow regimes. It identifies the inhibition of coalescence between rising bubbles and bubbles at rest at the free surface as a key mechanism responsible for the onset of foaming. A semi-empirical correlation for high viscosity fluids has been developed and good agreement with experimental data is found.
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Analysis of Transient Thickness of Pneumatic Foams
Chemical Engineering Science, 2002Co-Authors: Laurent Pilon, Andrei G. Fedorov, Raymond ViskantaAbstract:This paper presents a simple, experimentally validated approach to analyze the transient formation of a foam layer produced by injecting Gas bubbles into a foaming solution. Based on experimental observations, three different regimes in the transient growth of the foam have been identified as a function of the Superficial Gas Velocity. A model based on the mass conservation equation for the Gas phase in the foam combined with three different models for the average porosity is proposed. It is shown that for practical calculations a constant average porosity equal to 0.82 can be used. The model predictions show very good agreement with experimental data for low Superficial Gas Velocity and provide an upper limit of the foam thickness for intermediate and large Superficial Gas velocities. The paper discusses the physical mechanisms that may occur during the foam formation and the effects of the Superficial Gas Velocity on the foam dynamics. The present analysis speculates several mechanisms for the bursting of the bubbles at the top of the foams and proposes the framework for more fundamental and detailed studies.
M Jamialahmadi - One of the best experts on this subject based on the ideXlab platform.
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effect of Superficial Gas Velocity on bubble size terminal bubble rise Velocity and Gas hold up in bubble columns
Developments in Chemical Engineering and Mineral Processing, 2008Co-Authors: M Jamialahmadi, H MuullersteinhagenAbstract:It is important to have a reliable estimate of bubble size, terminal bubble rise Velocity and Gas hold-up in bubble columns, since these parameters are directly related to the transfer coefficients and the transfer area. Mean bubble diameters have been measured as a function of the Superficial Gas Velocity in air-water systems. In the bubbly flow regime, the bubble size is a strong function of the orifice diameter and the wettability of the Gas distributor and a weak function of Superficial Gas Velocity. In the turbulent churn flow regime this functionality is reversed and the bubble diameter becomes a strong function of the Superficial Gas Velocity. A correlation is presented which covers both regimes. The terminal bubble rise Velocity was measured as a function of the bubble size and the results were compared with correlations recommended in the literature. Finally, the Gas hold-up was measured over a wide range of Superficial Gas velocities. The results were compared with a variety of empirical and theoretical correlations. New equations are presented which predict Gas hold-up of the air-water system with good accuracy.
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Effect of Superficial Gas Velocity on Bubble Size, Terminal Bubble Rise Velocity and Gas Hold‐up in Bubble Columns
Developments in Chemical Engineering and Mineral Processing, 2008Co-Authors: M Jamialahmadi, H. Müuller-steinhagenAbstract:It is important to have a reliable estimate of bubble size, terminal bubble rise Velocity and Gas hold-up in bubble columns, since these parameters are directly related to the transfer coefficients and the transfer area. Mean bubble diameters have been measured as a function of the Superficial Gas Velocity in air-water systems. In the bubbly flow regime, the bubble size is a strong function of the orifice diameter and the wettability of the Gas distributor and a weak function of Superficial Gas Velocity. In the turbulent churn flow regime this functionality is reversed and the bubble diameter becomes a strong function of the Superficial Gas Velocity. A correlation is presented which covers both regimes. The terminal bubble rise Velocity was measured as a function of the bubble size and the results were compared with correlations recommended in the literature. Finally, the Gas hold-up was measured over a wide range of Superficial Gas velocities. The results were compared with a variety of empirical and theoretical correlations. New equations are presented which predict Gas hold-up of the air-water system with good accuracy.
Miguel A Galan - One of the best experts on this subject based on the ideXlab platform.
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influence of aspect ratio and Superficial Gas Velocity on the evolution of unsteady flow structures and flow transitions in a rectangular two dimensional bubble column
Industrial & Engineering Chemistry Research, 2006Co-Authors: Elena M Diaz, Francisco J Montes, Miguel A GalanAbstract:In this paper, the flow regimes developed in a centrally aerated two-dimensional (2D) bubble column are studied by means of visual observations and the measurement of wall pressure fluctuations. The combined effect of the aspect ratio (HIW) and Superficial Gas Velocity (U G ) on the hydrodynamics of the bubble column is investigated. Moreover, the time-averaged and time-dependent flow behavior are analyzed together. The results reveal the importance of H/W and U G on the developed flow regimes and the significance of the steadiness or unsteadiness of the flow on the resulting time-averaged flow regimes. A detailed description of the flow patterns based on HIW and U G is presented. As U G is increased, at H/W = 1.25, two pseudo-steady-state flow regimes (characterized by one or two circulation cells) are observed. At H/W = 2.25, only unsteady bubble plumes of decreasing oscillation period are obtained. At H/W = 1.50, 1.75, and 2.00, unsteady flow structures occur, at increasing values of U G .
