The Experts below are selected from a list of 309489 Experts worldwide ranked by ideXlab platform

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

  • discrete Phase Simulation of single bubble rise behavior at elevated pressures in a bubble column
    Chemical Engineering Science, 2000
    Co-Authors: Jianping Zhang, Liang-shih Fan
    Abstract:

    Abstract Numerical Simulation is performed on the flow behavior of a bubble rising in a liquid medium at high pressures. In the numerical scheme, a computational fluid dynamics (CFD) method is used to account for the flow characteristics of the continuous liquid Phase and the gas Phase inside the bubble. The volume tracking based on the volume-of-fluid (VOF) method is used to describe the free surface motion of gas bubble, and the deformational bubble shapes. Simulations are performed simultaneously for both liquid and gas Phases by considering the volume-fraction-weighted averaged properties on the interface. The behavior of a single gas bubble rising in Paratherm NF heat transfer liquid at pressures of 0.1 and 19.4 MPa is simulated and compared with the experimental results obtained in this study. The comparison is satisfactory. The results of the Simulation indicate that as the pressure increases, the maximum stable bubble size decreases, which is in conformity with the experimental findings.

  • Discrete Phase Simulation of gas–liquid–solid fluidization systems: single bubble rising behavior
    Powder Technology, 2000
    Co-Authors: Jianping Zhang, Liang-shih Fan
    Abstract:

    Abstract A computational scheme for discrete-Phase Simulation of a gas–liquid–solid fluidization system and a two-dimensional code based on it are developed in this study. In this scheme, the volume-averaged method, the dispersed particle method, and the volume-of-fluid (VOF) method are used to account for the flow of liquid, solid particles, and gas bubbles respectively. The gas–liquid interfacial mass, momentum and energy transfer is described by a continuum surface force (CSF) model. A close-distance interaction (CDI) model is introduced which illustrates the motion of the particle prior to its collision; upon collision, the hard sphere model is employed. The particle–bubble interaction is formulated by incorporating the surface tension force in the equation of motion of particles. The particle–liquid interaction is brought into the liquid Phase Navier–Stokes (N–S) equations through the use of Newton's third law of motion. The volume-averaged liquid Phase N–S equations are solved using the time-split two-step projection method. The Simulation results using this scheme are verified for bed expansion and pressure drop in liquid–solid fluidized beds. The Simulation of a single bubble rising in a liquid–solid suspension and the particle entrainment by a bubble on the surface of the bed is conducted and the results are in agreement with the experimental findings.

Jianping Zhang - One of the best experts on this subject based on the ideXlab platform.

  • discrete Phase Simulation of single bubble rise behavior at elevated pressures in a bubble column
    Chemical Engineering Science, 2000
    Co-Authors: Jianping Zhang, Liang-shih Fan
    Abstract:

    Abstract Numerical Simulation is performed on the flow behavior of a bubble rising in a liquid medium at high pressures. In the numerical scheme, a computational fluid dynamics (CFD) method is used to account for the flow characteristics of the continuous liquid Phase and the gas Phase inside the bubble. The volume tracking based on the volume-of-fluid (VOF) method is used to describe the free surface motion of gas bubble, and the deformational bubble shapes. Simulations are performed simultaneously for both liquid and gas Phases by considering the volume-fraction-weighted averaged properties on the interface. The behavior of a single gas bubble rising in Paratherm NF heat transfer liquid at pressures of 0.1 and 19.4 MPa is simulated and compared with the experimental results obtained in this study. The comparison is satisfactory. The results of the Simulation indicate that as the pressure increases, the maximum stable bubble size decreases, which is in conformity with the experimental findings.

  • Discrete Phase Simulation of gas–liquid–solid fluidization systems: single bubble rising behavior
    Powder Technology, 2000
    Co-Authors: Jianping Zhang, Liang-shih Fan
    Abstract:

    Abstract A computational scheme for discrete-Phase Simulation of a gas–liquid–solid fluidization system and a two-dimensional code based on it are developed in this study. In this scheme, the volume-averaged method, the dispersed particle method, and the volume-of-fluid (VOF) method are used to account for the flow of liquid, solid particles, and gas bubbles respectively. The gas–liquid interfacial mass, momentum and energy transfer is described by a continuum surface force (CSF) model. A close-distance interaction (CDI) model is introduced which illustrates the motion of the particle prior to its collision; upon collision, the hard sphere model is employed. The particle–bubble interaction is formulated by incorporating the surface tension force in the equation of motion of particles. The particle–liquid interaction is brought into the liquid Phase Navier–Stokes (N–S) equations through the use of Newton's third law of motion. The volume-averaged liquid Phase N–S equations are solved using the time-split two-step projection method. The Simulation results using this scheme are verified for bed expansion and pressure drop in liquid–solid fluidized beds. The Simulation of a single bubble rising in a liquid–solid suspension and the particle entrainment by a bubble on the surface of the bed is conducted and the results are in agreement with the experimental findings.

Edward J Maginn - One of the best experts on this subject based on the ideXlab platform.

  • a simple aimd approach to derive atomic charges for condensed Phase Simulation of ionic liquids
    Journal of Physical Chemistry B, 2012
    Co-Authors: Yong Zhang, Edward J Maginn
    Abstract:

    The atomic charges for two ionic liquids (ILs), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), were derived from periodic crystal Phase calculations with density functional theory (DFT) and plane wave basis sets (denoted as “AIMD-c charge”). For both ILs, the total charge was found to be ±0.8 e for the cation and anion, respectively, due to the charge transfer between ions and polarization caused by the environment. These atomic charges were used in a force field developed within the general Amber force field framework. Using this force field, static, dynamic, and thermodynamic properties were computed for the two ILs using molecular dynamics Simulation. The results were compared against results obtained using the same Amber force field but four different sets of partial charges, denoted as full charge, scaled charge, AIMD-l charge, and AIMD-b charge, respectively. The full charge was derived from quantum chemistry calcula...

  • A Simple AIMD Approach to Derive Atomic Charges for Condensed Phase Simulation of Ionic Liquids B
    The Journal of Physical Chemistry, 2012
    Co-Authors: Yong Zhang, Edward J Maginn
    Abstract:

    The atomic charges for two ionic liquids (ILs), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), were derived from periodic crystal Phase calculations with density functional theory (DFT) and plane wave basis sets (denoted as “AIMD-c charge”). For both ILs, the total charge was found to be ±0.8 e for the cation and anion, respectively, due to the charge transfer between ions and polarization caused by the environment. These atomic charges were used in a force field developed within the general Amber force field framework. Using this force field, static, dynamic, and thermodynamic properties were computed for the two ILs using molecular dynamics Simulation. The results were compared against results obtained using the same Amber force field but four different sets of partial charges, denoted as full charge, scaled charge, AIMD-l charge, and AIMD-b charge, respectively. The full charge was derived from quantum chemistry calculation of isolated ions in a vacuum and resulted in a total charge of unity on each ion. The scaled charge was obtained by uniformly scaling the full charge by 0.8. AIMD-l and AIMD-b charges were derived from liquid Phase ab initio molecular dynamics Simulations. The scaled charges have the same total charge on the ions as the AIMD-c charge but different distributions. It was found that Simulation results not only depend on the total charge of each ion, but they are also sensitive to the charge distribution within an ion, especially for dynamic and thermodynamic properties. Overall, for the two ILs under study, the AIMD-c charge was found to predict experimental results better than the other four sets of charges, indicating that fitting charges from crystal Phase DFT calculations, instead of extensive sampling of the liquid Phase configurations, is a simple and reliable way to derive atomic charges for condensed Phase ionic liquid Simulations.

Yong Zhang - One of the best experts on this subject based on the ideXlab platform.

  • a simple aimd approach to derive atomic charges for condensed Phase Simulation of ionic liquids
    Journal of Physical Chemistry B, 2012
    Co-Authors: Yong Zhang, Edward J Maginn
    Abstract:

    The atomic charges for two ionic liquids (ILs), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), were derived from periodic crystal Phase calculations with density functional theory (DFT) and plane wave basis sets (denoted as “AIMD-c charge”). For both ILs, the total charge was found to be ±0.8 e for the cation and anion, respectively, due to the charge transfer between ions and polarization caused by the environment. These atomic charges were used in a force field developed within the general Amber force field framework. Using this force field, static, dynamic, and thermodynamic properties were computed for the two ILs using molecular dynamics Simulation. The results were compared against results obtained using the same Amber force field but four different sets of partial charges, denoted as full charge, scaled charge, AIMD-l charge, and AIMD-b charge, respectively. The full charge was derived from quantum chemistry calcula...

  • A Simple AIMD Approach to Derive Atomic Charges for Condensed Phase Simulation of Ionic Liquids B
    The Journal of Physical Chemistry, 2012
    Co-Authors: Yong Zhang, Edward J Maginn
    Abstract:

    The atomic charges for two ionic liquids (ILs), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), were derived from periodic crystal Phase calculations with density functional theory (DFT) and plane wave basis sets (denoted as “AIMD-c charge”). For both ILs, the total charge was found to be ±0.8 e for the cation and anion, respectively, due to the charge transfer between ions and polarization caused by the environment. These atomic charges were used in a force field developed within the general Amber force field framework. Using this force field, static, dynamic, and thermodynamic properties were computed for the two ILs using molecular dynamics Simulation. The results were compared against results obtained using the same Amber force field but four different sets of partial charges, denoted as full charge, scaled charge, AIMD-l charge, and AIMD-b charge, respectively. The full charge was derived from quantum chemistry calculation of isolated ions in a vacuum and resulted in a total charge of unity on each ion. The scaled charge was obtained by uniformly scaling the full charge by 0.8. AIMD-l and AIMD-b charges were derived from liquid Phase ab initio molecular dynamics Simulations. The scaled charges have the same total charge on the ions as the AIMD-c charge but different distributions. It was found that Simulation results not only depend on the total charge of each ion, but they are also sensitive to the charge distribution within an ion, especially for dynamic and thermodynamic properties. Overall, for the two ILs under study, the AIMD-c charge was found to predict experimental results better than the other four sets of charges, indicating that fitting charges from crystal Phase DFT calculations, instead of extensive sampling of the liquid Phase configurations, is a simple and reliable way to derive atomic charges for condensed Phase ionic liquid Simulations.

Xu Guo-zheng - One of the best experts on this subject based on the ideXlab platform.

  • Three-Phase Modeling of Vacuum Circuit Breakers Switching off Shunt Reactors
    High Voltage Apparatus, 2010
    Co-Authors: Xu Guo-zheng
    Abstract:

    Aiming at the operating conditions of 40.5 kV vacuum circuit breaker switching off shunt reactors,and in order to eliminate deficiencies in the existing Simulation model,a general review of simulating researches on vacuum circuit breakers switching off small reactive current is given.A three-Phase model of 40.5 kV circuit breakers switching off shunt reactors is set up based on the experimental results of a type of 4.5 kV vacuum circuit breaker,including the dielectric strength characteristics,high-frequency current quenching criteria and chopping current.And the interPhase coupling is considered in the model.A three-Phase Simulation is conducted for the transient process of the vacuum circuit breaker switching off shunt reactors via ATP-EMTP,and the Simulation results coincide almost with experimental results.

  • Three-Phase Modeling of Vacuum Circuit Breakers Switching off Shunt Reactors
    High Voltage Apparatus, 2010
    Co-Authors: Xu Guo-zheng
    Abstract:

    Aiming at the operating conditions of 40.5 kV vacuum circuit breaker switching off shunt reactors,and in order to eliminate deficiencies in the existing Simulation model,a general review of simulating researches on vacuum circuit breakers switching off small reactive current is given.A three-Phase model of 40.5 kV circuit breakers switching off shunt reactors is set up based on the experimental results of a type of 4.5 kV vacuum circuit breaker,including the dielectric strength characteristics,high-frequency current quenching criteria and chopping current.And the interPhase coupling is considered in the model.A three-Phase Simulation is conducted for the transient process of the vacuum circuit breaker switching off shunt reactors via ATP-EMTP,and the Simulation results coincide almost with experimental results.