The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

S. L. Soo - One of the best experts on this subject based on the ideXlab platform.

Liang-shih Fan - One of the best experts on this subject based on the ideXlab platform.

  • Bubble formation in high‐pressure liquid–Solid Suspensions with plenum pressure fluctuation
    AIChE Journal, 2000
    Co-Authors: G. Q. Yang, Xukun Luo, Raymond Lau, Liang-shih Fan
    Abstract:

    The behavior of bubble formation from a single orifice in a nonaqueous liquid and a liquid–Solid suspension with pressure fluctuations in the gas chamber (plenum region) is studied at high pressures (up to 8.3 MPa). An analytical model is developed to account for the initial bubble size in liquid–Solid Suspensions at high pressures. The model takes into consideration various forces induced by particles, such as suspension inertial force. Both experiments and model predictions indicate that the initial bubble size in the suspension is generally larger than that in the liquid, and that it increases with an increase in the Solids concentration. The system pressure has a significant effect on the initial bubble size in liquids or liquid–Solid Suspensions when bubbles are formed under variable gas flow-rate conditions, and a negligible effect under constant gas flow-rate conditions. This model can reasonably describe the initial bubble sizes under high-pressure conditions measured experimentally in this study and those reported in the literature.

  • some aspects of high pressure phenomena of bubbles in liquids and liquid Solid Suspensions
    Chemical Engineering Science, 1999
    Co-Authors: Liang-shih Fan, D.j. Lee, G. Q. Yang, Katsumi Tsuchiya, Xukun Luo
    Abstract:

    Abstract Some aspects of bubble dynamics and macroscopic hydrodynamic properties in high-pressure bubble columns and three-phase fluidization systems are discussed. Experimental results along with discrete-phase simulations of a single bubble rising in liquids and liquid–Solid Suspensions at high pressures are presented. A mechanistic model is described, which accounts for the initial size of bubble from a single orifice in liquid–Solid Suspensions. The mechanism for bubble breakup at high pressures is illustrated by considering bubble instability induced by internal gas circulation inside a bubble, and an analytical expression is obtained to quantify the maximum stable bubble size. Experimental examinations on the roles of bubbles of different sizes indicate the importance of large bubbles in dictating the macroscopic hydrodynamics of slurry bubble columns. Further, extensive studies are made of the key macroscopic hydrodynamic properties, including moving packed bed phenomena, flow regime transition, overall gas holdup, mean bubble size, and bubble size distribution. An empirical correlation is introduced which predicts the gas holdup in slurry bubble columns of different scales. A similarity rule is revealed for the overall hydrodynamics of high-pressure slurry bubble columns, which takes into account the operating conditions, the maximum stable bubble size, and the physical properties of the gas, liquid, and Solids. The heat transfer characteristics under high pressures are also investigated. A consecutive film and surface renewal model is used to characterize the heat transfer mechanism.

  • Some aspects of high-pressure phenomena of bubbles in liquids and liquid–Solid Suspensions
    Chemical Engineering Science, 1999
    Co-Authors: Liang-shih Fan, D.j. Lee, G. Q. Yang, Katsumi Tsuchiya, Xukun Luo
    Abstract:

    Abstract Some aspects of bubble dynamics and macroscopic hydrodynamic properties in high-pressure bubble columns and three-phase fluidization systems are discussed. Experimental results along with discrete-phase simulations of a single bubble rising in liquids and liquid–Solid Suspensions at high pressures are presented. A mechanistic model is described, which accounts for the initial size of bubble from a single orifice in liquid–Solid Suspensions. The mechanism for bubble breakup at high pressures is illustrated by considering bubble instability induced by internal gas circulation inside a bubble, and an analytical expression is obtained to quantify the maximum stable bubble size. Experimental examinations on the roles of bubbles of different sizes indicate the importance of large bubbles in dictating the macroscopic hydrodynamics of slurry bubble columns. Further, extensive studies are made of the key macroscopic hydrodynamic properties, including moving packed bed phenomena, flow regime transition, overall gas holdup, mean bubble size, and bubble size distribution. An empirical correlation is introduced which predicts the gas holdup in slurry bubble columns of different scales. A similarity rule is revealed for the overall hydrodynamics of high-pressure slurry bubble columns, which takes into account the operating conditions, the maximum stable bubble size, and the physical properties of the gas, liquid, and Solids. The heat transfer characteristics under high pressures are also investigated. A consecutive film and surface renewal model is used to characterize the heat transfer mechanism.

  • Single bubble formation in high pressure liquid—Solid Suspensions
    Powder Technology, 1998
    Co-Authors: Xukun Luo, G. Q. Yang, D.j. Lee, Liang-shih Fan
    Abstract:

    Abstract Bubble formation from a single nozzle is investigated analytically and experimentally in nonaqueous liquid and liquid—Solid Suspensions at pressures up to 17.3 MPa. A mechanistic model is proposed to predict the initial bubble size in liquid—Solid Suspensions, by taking into account the various forces affecting the bubble growth including those induced by the presence of the particles, such as the suspension inertial force and the particle-bubble collision force. It is found that the initial bubble size in the Suspensions is generally larger than that in the liquid mainly due to the inertia effect of the suspension. The initial bubble size increases with the Solids holdup. The pressure has an insignificant effect on the initial bubble size in both the liquid and liquid—Solid Suspensions under the conditions of this study. The model can reasonably predict the initial bubble sizes obtained in this study and those reported in the literature.

  • On the rise velocity of bubbles in liquid-Solid Suspensions at elevated pressure and temperature
    Chemical Engineering Science, 1997
    Co-Authors: Xukun Luo, Katsumi Tsuchiya, Jian Zhang, Liang-shih Fan
    Abstract:

    Experiments are conducted to measure the rise velocity of single bubbles in liquid-Solid Suspensions at pressures up to 17 MPa and temperatures up to 88°C over the bubble size range from 1 to 20 mm. It is found that the bubble rise velocity decreases with increasing pressure and with decreasing temperature. The decrease of bubble rise velocity is due mainly to the variations of gas density and liquid viscosity with pressure and temperature. The presence of Solid particles also reduces the rise velocity; the extent of reduction can be examined in terms of an increase in the apparent suspension viscosity by applying the homogeneous, Newtonian analogy. A mechanistic model is developed which considers a balance of forces acting on a single bubble, including the impact force due to Solid particles, as well as buoyancy, gravity and liquid drag forces. Comparisons between the model predictions and the experimental data on the bubble rise velocity in liquid-Solid fluidized beds are shown to be satisfactory.

Vicente Garzo - One of the best experts on this subject based on the ideXlab platform.

  • kinetic theory of shear thickening for a moderately dense gas Solid suspension from discontinuous thickening to continuous thickening
    Physical Review E, 2017
    Co-Authors: Hisao Hayakawa, Satoshi Takada, Vicente Garzo
    Abstract:

    The Enskog kinetic theory for moderately dense gas-Solid Suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the environmental fluid on Solid particles is modeled via a viscous drag force plus a stochastic Langevin-like term. The Enskog equation is solved by means of two independent but complementary routes: (i) Grad's moment method and (ii) event-driven Langevin simulation of hard spheres. Both approaches clearly show that the flow curve (stress-strain rate relation) depends significantly on the volume fraction of the Solid particles. In particular, as the density increases, there is a transition from the discontinuous shear thickening (observed in dilute gases) to the continuous shear thickening for denser systems. The comparison between theory and simulations indicates that while the theoretical predictions for the kinetic temperature agree well with simulations for densities φ≲0.5, the agreement for the other rheological quantities (the viscosity, the stress ratio, and the normal stress differences) is limited to more moderate densities (φ≲0.3) if the inelasticity during collisions between particles is not large.

David J. Parker - One of the best experts on this subject based on the ideXlab platform.

  • Hydrodynamics and particle motion in upward flowing dense particle Suspensions: Application in solar receivers
    Chemical Engineering Science, 2016
    Co-Authors: Pablo García-triñanes, Thomas Leadbeater, Benjamin Boissière, Renaud Ansart, Jonathan Seville, David J. Parker
    Abstract:

    Dense gas–Solid Suspensions have the potential to be applied as heat transfer fluids (HTF) for energy collection and storage in concentrated solar power plants. At the heart of these systems is the solar receiver, composed of a bundle of tubes which contain the Solid suspension used as the thermal energy carrier. In the design investigated here, the particles form a dense upward-flowing suspension. Both density of the suspension of these particles and their movement have a strong influence on the heat transfer. An apparatus was designed to replicate the hydrodynamic and particle motion in the real solar energy plant at ambient temperature. The governing parameters of the flow were established as the Solid feeding flow rate, the fluidisation velocity, the Solids holdup, the freeboard pressure and the secondary air injection (aeration) velocity. In the case studied, aeration was applied with air introduced into the uplift transport tube some way up its length. This study finds that the amount of this secondary air injection is the most important parameter for the stability and the uniform distribution of the Solids flow in the tubes. Solids motion was measured using the non-invasive positron emission particle tracking (PEPT) technique to follow the movement of a 60 mm tracer particle, onto which was adsorbed the positron emitting 18F radioisotope. Analysis of the resulting three-dimensional trajectories provides information on Solids flow pattern and Solids velocity. Results show the overall behaviour of the bulk material in detail: small step-wise movements associated with bubble motion superimposed on a general trend of upward flow in the centre and downward flow close to the walls. These findings suggest that this particular type of flow is ideal for transporting energy from the walls of the solar receiver tubes

Chao Zhu - One of the best experts on this subject based on the ideXlab platform.

  • Oblique Evaporating Sprays in Gas-Solid Suspensions
    Volume 1: Fora Parts A and B, 2002
    Co-Authors: Chao Zhu, Guangliang Liu, Xiaohua Wang
    Abstract:

    Evaporating sprays in gas-Solid flows are constantly encountered in many industry processes, such as Fluid Catalytic Cracking in petroleum industry and condensed mode operation of polyethylene polymerization in polymer industry. The rapid evaporation of droplets in a gas-Solid suspension flow can have significant effects on the gas-Solid mixing near the spray nozzle regions. Typical effects of evaporating jets on gas-Solid dynamics include the change of velocity of gas and Solids phases, dilution effect on Solids concentration, temperature reduction of all phases. On the other hand, the particle loading in the gas-Solid flow can also significantly change the spray structures such as spray evaporation region, evaporation rate, and collision frequency among droplets and Solids. In this paper, experimental as well as theoretical studies on evaporating liquid nitrogen spray into an air-particulate suspension flow are performed. Using laser enhanced visualization system and thermocouple profile probes, we obtain the spray trajectory and temperature distribution in the test section. A comprehensive analytic model has been developed to study the parametric effects of phase interactions with phase changes in all three phases. The study shows that the particle loading can considerably affect the spray structure. Inversely, the sprays also significantly change the velocity, concentration and temperature fields of the gas-Solid flow. Both qualitative and quantitative comparisons give a good agreement between experimental results and modeling simulations.Copyright © 2002 by ASME

  • Statistical properties of unsteady gas-Solid Suspensions with strong particle-particle interactions in horizontal pipe flows
    Powder Technology, 1992
    Co-Authors: Chao Zhu, S. L. Soo
    Abstract:

    Abstract Unsteady stratified motions in gas-Solid Suspensions with strong particle-particle interactions at low velocities were observed, but the means for pred

  • A modified theory for electrostatic probe measurements of particle mass flows in dense gas‐Solid Suspensions
    Journal of Applied Physics, 1992
    Co-Authors: Chao Zhu, S. L. Soo
    Abstract:

    Measurements of mass flows of a dense gas‐Solid suspension have led to a modification of the electrostatic probe theory. Previous ball probe theory based on dilute gas‐Solid Suspensions has been extended to account for the effects of multiple scattering and sliding when applied to a dense gas‐Solid suspension. The validation of the theory was shown by the experimental results.