The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Youjun Lu - One of the best experts on this subject based on the ideXlab platform.
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bubble dynamic wave velocity in Fluidized Bed
Chemical Engineering Science, 2016Co-Authors: Youjun LuAbstract:Abstract Experimental and numerical investigations have validated that the supercritical water (SCW) Fluidized Bed has bubbling fluidization state, which obviously diverges from the classical gas–solid Fluidized Bed. It is difficult to apply the classical bubbling parameters including diameter and rising velocity to characterise the bubbles within the SCW Fluidized Bed due to the unattainable measurements in the high temperature and pressure conditions. This paper derived bubble dynamic wave (BDW) velocity to establish a theoretical description of the bubbling characteristics for different bubbling systems. The BDW velocity is a propagation velocity of interface wave between bubble and emulsion phase induced by the perturbation of bubble volume. The expression of the BDW velocity was derived by treating emulsion phase as compressible fluid. The BDW velocity of the SCW Fluidized Bed (intermediate fluidization) shows an intermediate value between air or steam–solid system (classical bubbling fluidization) and ambient water–solid system (classical homogenous fluidization). Further, the BDW energy was derived to characterise the fluid dynamic in meso-scale. The variation trend of BDW energy with superficial velocity was consistent with that of the measured meso-scale energy of differential pressure fluctuation signals. This paper provided a new parameter of BDW velocity for describing the characteristics of bubbling Fluidized Bed.
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Bed to wall heat transfer in supercritical water Fluidized Bed: Comparison with the gas–solid Fluidized Bed
Applied Thermal Engineering, 2015Co-Authors: Youjun Lu, Tianning Zhang, Xubin DongAbstract:Abstract Supercritical water (SCW) Fluidized Bed is a new reactor concept for gasification of wet biomass. In this paper, the Eulerian two-fluid model based on Kinetic Theory of Granular Flow in Fluidized Bed was established, and the physical model of movement of single bubble up the wall was adopted. The comparison studies of particle distribution, temperature distribution and transient heat transfer characteristics between the SCW and gas–solid Fluidized Bed were carried out. The results show that the bubble diameter and rise velocity in SCW Fluidized Bed are smaller than those in gas–solid Fluidized Bed. With the increasing solid volume fraction near the wall, the Bed-to-wall heat transfer coefficient decreases in SCW Fluidized Bed, while it increases in gas–solid Fluidized Bed. What is more, the Bed-to-wall heat transfer coefficient is sensitive to superficial velocity where the solid volume fraction is low, which is different from that in gas–solid Fluidized Bed.
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Flow structure and bubble dynamics in supercritical water Fluidized Bed and gas Fluidized Bed: A comparative study
International Journal of Multiphase Flow, 2015Co-Authors: Youjun Lu, Jikai Huang, Pengfei Zheng, Dengwei JingAbstract:Abstract Supercritical water (SCW) Fluidized Bed is a new reactor concept for hydrogen production from biomass or coal gasification. In this paper, a comparative study on flow structure and bubble dynamics in a supercritical water Fluidized Bed and a gas Fluidized Bed was carried out using the discrete element method (DEM). The results show that supercritical water condition reduces the incipient fluidization velocity, changes regime transitions, i.e. a homogeneous fluidization was observed when the superficial velocity is in the range of the minimum fluidization velocity and minimum bubbling velocity even the solids behave as Geldart B powders in the gas Fluidized Bed. Bubbling fluidization in the supercritical water Fluidized Bed was formed after superficial velocity exceeds the minimum bubbling velocity, as in the gas Fluidized Bed. Bubble is one of the most important features in Fluidized Bed, which is also the emphasis in this paper. Bubble growth was effectively suppressed in the supercritical water Fluidized Bed, which resulted in a more uniform flow structure. By analyzing a large number of bubbles, bubble dynamic characteristics such as diameter distribution, frequency, rising path and so on, were obtained. It is found that bubble dynamic characteristics in the supercritical water Fluidized Bed differ a lot from that in the gas Fluidized Bed, and there is a better fluidization quality induced by the bubble dynamics in the supercritical water Fluidized Bed.
Dengwei Jing - One of the best experts on this subject based on the ideXlab platform.
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Flow structure and bubble dynamics in supercritical water Fluidized Bed and gas Fluidized Bed: A comparative study
International Journal of Multiphase Flow, 2015Co-Authors: Youjun Lu, Jikai Huang, Pengfei Zheng, Dengwei JingAbstract:Abstract Supercritical water (SCW) Fluidized Bed is a new reactor concept for hydrogen production from biomass or coal gasification. In this paper, a comparative study on flow structure and bubble dynamics in a supercritical water Fluidized Bed and a gas Fluidized Bed was carried out using the discrete element method (DEM). The results show that supercritical water condition reduces the incipient fluidization velocity, changes regime transitions, i.e. a homogeneous fluidization was observed when the superficial velocity is in the range of the minimum fluidization velocity and minimum bubbling velocity even the solids behave as Geldart B powders in the gas Fluidized Bed. Bubbling fluidization in the supercritical water Fluidized Bed was formed after superficial velocity exceeds the minimum bubbling velocity, as in the gas Fluidized Bed. Bubble is one of the most important features in Fluidized Bed, which is also the emphasis in this paper. Bubble growth was effectively suppressed in the supercritical water Fluidized Bed, which resulted in a more uniform flow structure. By analyzing a large number of bubbles, bubble dynamic characteristics such as diameter distribution, frequency, rising path and so on, were obtained. It is found that bubble dynamic characteristics in the supercritical water Fluidized Bed differ a lot from that in the gas Fluidized Bed, and there is a better fluidization quality induced by the bubble dynamics in the supercritical water Fluidized Bed.
Jujun Ruan - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamics of Plasma Fluidized Bed
Plasma Fluidized Bed, 2018Co-Authors: Changming Du, Jujun RuanAbstract:This chapter systematically reviews the hydrodynamics of plasma Fluidized Bed and its progress. Firstly, the hydrodynamics of plasma spouted Bed is introduced from the aspects of minimum spouted velocity, spoutable height, pressure drop and particle attrition, and the relevant formulas are given. Finally, the hydrodynamics of plasma Fluidized Bed was analyzed.
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Thermal Plasma Fluidized Bed
Plasma Fluidized Bed, 2018Co-Authors: Changming Du, Jujun RuanAbstract:In this chapter, the thermal plasma Fluidized Bed is introduced in detail. The thermal plasma Fluidized Bed includes: DC plasma jet spouted Bed, AC plasma jet Fluidized Bed, radio frequency discharge (RF) Fluidized Bed (RF plasma Fluidized Bed, RF plasma circulating Fluidized Bed, RF downer Bed), microwave discharge Fluidized Bed and electrothermal plasma Fluidized Bed. Moreover, this chapter introduces the research progress and applications of various reactors, and points out the shortcomings of these reactors.
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Plasma and Plasma Fluidized Bed
Plasma Fluidized Bed, 2018Co-Authors: Changming Du, Jujun RuanAbstract:In this chapter, the topic of plasma is introduced and a comprehensive description of plasma Fluidized Bed is given. The development and application of thermal plasma and non-thermal plasma are briefly introduced. Then, the development course of plasma Fluidized Bed is introduced in chronological order. What’s more, the principle of the removal of pollutants by plasma Fluidized Bed is descriBed, and the advantages of the plasma Fluidized Bed are listed in detail. It’s proved that the plasma Fluidized Bed has great potential. In the end, three sets of parameters of plasma Fluidized Bed are evaluated for the use of plasma Fluidized Bed.
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Non-thermal Plasma Fluidized Bed
Plasma Fluidized Bed, 2018Co-Authors: Changming Du, Jujun RuanAbstract:In this chapter, the non-thermal plasma Fluidized Bed is introduced in detail. The thermal plasma Fluidized Bed includes gliding arc discharge Fluidized Bed, dielectric barrier discharge plasma Fluidized Bed, corona discharge plasma Fluidized Bed. Moreover, this chapter also introduces the research progress and applications of various reactors, and points out the existing shortcomings of them.
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Discharge Characteristic in the Plasma Fluidized Bed
Plasma Fluidized Bed, 2018Co-Authors: Changming Du, Jujun RuanAbstract:In this chapter, the discharge characteristics of plasma Fluidized Bed are descriBed in detail. Firstly, this chapter presents the factors that may affect the discharge of plasma Fluidized Bed. Then, the research status of discharge characteristics of plasma Fluidized Bed is analyzed, and the research on discharge characteristics is still lacking, so a lot of research is needed.
Xubin Dong - One of the best experts on this subject based on the ideXlab platform.
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Bed to wall heat transfer in supercritical water Fluidized Bed: Comparison with the gas–solid Fluidized Bed
Applied Thermal Engineering, 2015Co-Authors: Youjun Lu, Tianning Zhang, Xubin DongAbstract:Abstract Supercritical water (SCW) Fluidized Bed is a new reactor concept for gasification of wet biomass. In this paper, the Eulerian two-fluid model based on Kinetic Theory of Granular Flow in Fluidized Bed was established, and the physical model of movement of single bubble up the wall was adopted. The comparison studies of particle distribution, temperature distribution and transient heat transfer characteristics between the SCW and gas–solid Fluidized Bed were carried out. The results show that the bubble diameter and rise velocity in SCW Fluidized Bed are smaller than those in gas–solid Fluidized Bed. With the increasing solid volume fraction near the wall, the Bed-to-wall heat transfer coefficient decreases in SCW Fluidized Bed, while it increases in gas–solid Fluidized Bed. What is more, the Bed-to-wall heat transfer coefficient is sensitive to superficial velocity where the solid volume fraction is low, which is different from that in gas–solid Fluidized Bed.
Wan Ramli Wan Daud - One of the best experts on this subject based on the ideXlab platform.
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Fluidized Bed Dryers — Recent Advances
Advanced Powder Technology, 2008Co-Authors: Wan Ramli Wan DaudAbstract:Although industrial Fluidized Bed dryers have been used successfully for the drying of wet solid particles for many years, the development of industrial Fluidized Bed dryers for any particular application is fraught with difficulties such as scaling-up, poor fluidization and non-uniform product quality. Scaling-up is the major problem and there are very few good, reliable theoretical models that can replace the expensive laboratory work and pilot-plant trials. This problem is mainly due to the different behavior of bubbles and mixing regimes in Fluidized Bed dryers of different size. Simple transformation of laboratory batch drying data to continuous back-mixed dryers using the residence time distribution of the solids is insufficient to account for the complex flow and heat and mass transfer phenomena occurring in the Bed. Although time scaling using temperature driving forces and solids mass flux for the same change in moisture content in the batch and continuous dryers has been successful in predicting moisture content profiles in the continuous dryer at the constant rate period, it does not take into account solid mixing. Two-phase Davidson–Harrison models have been used in modeling of the continuous back-mixed dryer with various degrees of success. On the other hand, the three-phase Kunii–Levenspiel model is seldom used in modeling Fluidized Bed dryers because it is too complex to handle. A combination of multi-phase models and residence time distribution could improve predicting power for back-mixed dryers because this combination takes into account both the bubbles and solid mixing phenomena. Incremental models were widely used to model continuous plug flow Fluidized Bed dryers, but the cross-flow of drying medium has not been sufficiently modeled except by the author. In some incremental models, axial dispersion is modeled using the Peclet number, Pe. A combination of an incremental model with an axial dispersion and cross-flow model of drying medium would improve predicting power. Poor fluidization of Geldart group C particles could be improved by the assistance of external means such as vibration, agitation, rotation and centrifugation. Both vibrated and agitated Fluidized Bed dryers have been successfully used in industry, but rotating or centrifugal Fluidized Bed dryers are still not available for industrial use.
