UBC

PDF Research Fellow

Publications
Yulong Ding, Ryan Anderson, Lifeng Zhang, Xiaotao Bi, David P. Wilkinson, Simulations of two-phase flow distribution in communicating parallel channels for a PEM fuel cell, International Journal of Multiphase Flow, 2013,52,35-45.
Zhang L.F., Jiangtian Hou, Xiaotao T. Bi, John R. Grace, Travis Janke, Claudio Arator, Experiments on Charge Generation due to Particle-Particle and Particle-Wall Contact in Powder Mixtures, Particuology, 2012, doi:10.1016/j.partic.2011.07.006
Zhang L.F., Jiangtian Hou, Xiaotao T. Bi, John R. Grace, Travis Janke, Claudio Arator, Fluidization characterization and charging behavior of fly ash in a vibrated fluidized bed, Powder Technology, 2011, doi:10.1016/j.powtec.2011.10.005.
Zhang L.F., Xiaotao Bi, David P. Wilkinson, Ryan Anderson, Jurgen Stumper, Haijiang Wang, Gas-liquid Two-phase Flow Behaviour in Minichannels Bounded with a Permeable Wall, Chemical Engineering Science, 2011, 66, 3377-3385.
Anderson R., Zhang L.F., Ding Y., Blanco M., Bi, H.T., Wilkinson D.P., A Critical Review of Two-phase Flow in Gas Flow Channels of PEM Fuel Cells, Journal of Power Sources, 2010, 195, 4531-4553.
Anderson R., Wilkinson D.P., Bi, H.T., Zhang L.F., Two-phase Flow Pressure Drop Hysteresis in Parallel Channels of PEM Fuel Cell Flow Fields, Journal of Power Sources, 2010, 195, 4168-4176.
Du, W., Zhang, L.F., Bi, H.T., Wilkinson, D.P., Stumper, J., Wang, H.J., Gas-liquid two-phase flow in mini-channels with liquid side introduction , Ind. Eng. Chem. Res., 2010, 49(15), 6709-6721.
Zhang, L.F., Bi, H.T., Wilkinson D.P., Stumper, J., Wang, H.J., Journal of Power Sources, 2010, 195, 10, 3121-3129.
Zhang L.F., Du W., Bi H.T., Wilkinson D.P., Stumper J., Wang H.J., Gas Liquid Flow Distributions in Parallel Channels for Fuel Cells, Journal of Power Sources, 2009, 189(2), 1023-1031.
Zhang L.F., Bi H.T., Wilkinson D.P., Stumper J., Wang, H.J., Journal of Power Sources, 2008, 183(2), 643-650.

RES Group Inc.

Project Engineer

RES Group provides innovative technical solutions to high-value scientific & engineering problems for leading companies around the world in energy & chemicals, automotives & fuels, and pharmaceuticals.

http://resgroupinc.com/

Singapore- MIT Alliance

Research Intern

Lifeng worked at Singapore- MIT Alliance as a Research Intern

University of Saskatchewan

Associate Professor

Lifeng worked at University of Saskatchewan as a Associate Professor

University of Saskatchewan

Assistant Professor

Lifeng worked at University of Saskatchewan as a Assistant Professor

University of Waterloo

Research Assistant

Publications
Zhang L.F., Pan Q.M., Rempel G.L., Hydrogenation of Unsaturated Polymers in a Multistage Agitated Contactor: Experiments and Numerical Simulation, Chemical Engineering Science, 2010, 65, 6, 2027-2036.
Zhang L.F., Pan Q.M., Rempel G.L., Residence Time Distribution in a Multistage Agitated Contactor: CFD Prediction and Experimental Validation, Ind. Eng. Chem. Res., 2007, 46(11), 3538-3546.
Zhang L.F., Pan Q.M., Rempel G.L., Liquid Phase Mixing and Gas Hold-up in a Multistage Agitated Contactor with Cocurrent Upflow: Air/Viscous Fluids, Chemical Engineering Science, 2006, 61, 6189-6198.
Zhang L.F., Pan Q.M., Rempel G.L., Liquid Phase Mixing and Gas Hold-up in a Multistage Agitated Contactor with Cocurrent Upflow, Ind. Eng. Chem. Res., 2005, 44(14), 5304-5311.
Zhang L.F., Pan Q.M., Rempel G.L., A Hydrodynamic Study and Mass Transfer Coefficient on a Multistage Agitated Contactor with Cocurrent Gas Liquid Upflow, the 7th World Congress of Chemical Engineering, 10-14 July, 2005, Glasgow, Scotland, no. 05-003, 10 pages.
Zhang L.F., Pan, Q.M., Rempel G.L., Modeling and Simulation of a Multistage Agitated Contactor for Hydrogenation of Nitrile Butadiene Rubber, International Journal of Chemical Reactor Engineering, 2005, A9.
Patent
Zhang L., Pan Q., Rempel G., Continuous Hydrogenation Process of Unsaturated Polymers, EP 08161101.4. (Granted in July 2009)

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Bifurcation analysis and multiplicity of steady states in a multistage agitated contactor for gas-liquid processes

The Canadian Journal of Chemical Engineering

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors.

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Bifurcation analysis and multiplicity of steady states in a multistage agitated contactor for gas-liquid processes

The Canadian Journal of Chemical Engineering

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors.

Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

International Journal of Hydrogen Energy

Water is an inevitable byproduct in proton exchange membrane fuel cells that can lead to complex two-phase flow throughout the cell's components, including the flow field channels utilized for gas delivery. A modified Lockhart–Martinelli (LM) approach based on unique water introduction through the gas diffusion layer is used here to predict the gas–liquid pressure drop in these channels by modifying the Chisholm parameter C. This paper exclusively uses experimental data of two-phase flow multipliers from four sources in the literature, all of which are obtained from active fuel cell operation. C does not appear to change strongly as a function of temperature, relative humidity, or air stoichiometry, but does vary significantly with the current density. This is especially true at low current densities (<500 mA cm−2). To capture this behavior, C is defined as a flow regime dependent parameter based on a flow regime map from the active fuel cell data. In addition to the traditionally used slug, film, and single-phase regimes, an ‘accumulating’ flow regime is proposed to capture the behavior of C and two-phase flow multipliers at low current densities. The proposed accumulating flow regime is consistent with visual observation reported in the literature. In addition, the developed LM approach can be employed to optimize fuel cell flow field design and operation.

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Bifurcation analysis and multiplicity of steady states in a multistage agitated contactor for gas-liquid processes

The Canadian Journal of Chemical Engineering

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors.

Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

International Journal of Hydrogen Energy

Water is an inevitable byproduct in proton exchange membrane fuel cells that can lead to complex two-phase flow throughout the cell's components, including the flow field channels utilized for gas delivery. A modified Lockhart–Martinelli (LM) approach based on unique water introduction through the gas diffusion layer is used here to predict the gas–liquid pressure drop in these channels by modifying the Chisholm parameter C. This paper exclusively uses experimental data of two-phase flow multipliers from four sources in the literature, all of which are obtained from active fuel cell operation. C does not appear to change strongly as a function of temperature, relative humidity, or air stoichiometry, but does vary significantly with the current density. This is especially true at low current densities (<500 mA cm−2). To capture this behavior, C is defined as a flow regime dependent parameter based on a flow regime map from the active fuel cell data. In addition to the traditionally used slug, film, and single-phase regimes, an ‘accumulating’ flow regime is proposed to capture the behavior of C and two-phase flow multipliers at low current densities. The proposed accumulating flow regime is consistent with visual observation reported in the literature. In addition, the developed LM approach can be employed to optimize fuel cell flow field design and operation.

Pressure drop and pressure fluctuations in spouted beds with binary mixtures of particles

Powder Technology

When handling fine particles in spouted beds, addition of coarse particles has shown improved spouting stability than single particle systems. However, segregation may still occur because of insufficient mixing in binary mixtures, which will adversely influence the process performance. Therefore, in this study, analysis of pressure drop and its fluctuation signals were for the first time used to understand mechanisms of flow regime transitions in spouted beds with binary mixtures. The results showed that the typical varying sequence of pressure drop can be observed for spouted bed with binary mixtures and the peak pressure drop is related to the mixing degree of particles, which is mainly influenced by the inter-particle forces between fine particles and their counterpart coarse ones. The statistic characteristics of pressure drop time series, i.e., average value, standard deviation and probability distributions, were found to vary for different flow regimes. Therefore, they could be used for the characterization of these flow regimes. The spouting stability of binary mixtures can be reflected by power spectrum analysis; the influences of particles size and density difference on spouting stability were discussed through power spectral analysis.

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Bifurcation analysis and multiplicity of steady states in a multistage agitated contactor for gas-liquid processes

The Canadian Journal of Chemical Engineering

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors.

Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

International Journal of Hydrogen Energy

Water is an inevitable byproduct in proton exchange membrane fuel cells that can lead to complex two-phase flow throughout the cell's components, including the flow field channels utilized for gas delivery. A modified Lockhart–Martinelli (LM) approach based on unique water introduction through the gas diffusion layer is used here to predict the gas–liquid pressure drop in these channels by modifying the Chisholm parameter C. This paper exclusively uses experimental data of two-phase flow multipliers from four sources in the literature, all of which are obtained from active fuel cell operation. C does not appear to change strongly as a function of temperature, relative humidity, or air stoichiometry, but does vary significantly with the current density. This is especially true at low current densities (<500 mA cm−2). To capture this behavior, C is defined as a flow regime dependent parameter based on a flow regime map from the active fuel cell data. In addition to the traditionally used slug, film, and single-phase regimes, an ‘accumulating’ flow regime is proposed to capture the behavior of C and two-phase flow multipliers at low current densities. The proposed accumulating flow regime is consistent with visual observation reported in the literature. In addition, the developed LM approach can be employed to optimize fuel cell flow field design and operation.

Pressure drop and pressure fluctuations in spouted beds with binary mixtures of particles

Powder Technology

When handling fine particles in spouted beds, addition of coarse particles has shown improved spouting stability than single particle systems. However, segregation may still occur because of insufficient mixing in binary mixtures, which will adversely influence the process performance. Therefore, in this study, analysis of pressure drop and its fluctuation signals were for the first time used to understand mechanisms of flow regime transitions in spouted beds with binary mixtures. The results showed that the typical varying sequence of pressure drop can be observed for spouted bed with binary mixtures and the peak pressure drop is related to the mixing degree of particles, which is mainly influenced by the inter-particle forces between fine particles and their counterpart coarse ones. The statistic characteristics of pressure drop time series, i.e., average value, standard deviation and probability distributions, were found to vary for different flow regimes. Therefore, they could be used for the characterization of these flow regimes. The spouting stability of binary mixtures can be reflected by power spectrum analysis; the influences of particles size and density difference on spouting stability were discussed through power spectral analysis.

A Critical Review of Two-phase Flow in Gas Flow Channels of PEM Fuel Cells

Journal of Power Sources, 195 (15) 4531-4553 (2010)

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Bifurcation analysis and multiplicity of steady states in a multistage agitated contactor for gas-liquid processes

The Canadian Journal of Chemical Engineering

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors.

Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

International Journal of Hydrogen Energy

Water is an inevitable byproduct in proton exchange membrane fuel cells that can lead to complex two-phase flow throughout the cell's components, including the flow field channels utilized for gas delivery. A modified Lockhart–Martinelli (LM) approach based on unique water introduction through the gas diffusion layer is used here to predict the gas–liquid pressure drop in these channels by modifying the Chisholm parameter C. This paper exclusively uses experimental data of two-phase flow multipliers from four sources in the literature, all of which are obtained from active fuel cell operation. C does not appear to change strongly as a function of temperature, relative humidity, or air stoichiometry, but does vary significantly with the current density. This is especially true at low current densities (<500 mA cm−2). To capture this behavior, C is defined as a flow regime dependent parameter based on a flow regime map from the active fuel cell data. In addition to the traditionally used slug, film, and single-phase regimes, an ‘accumulating’ flow regime is proposed to capture the behavior of C and two-phase flow multipliers at low current densities. The proposed accumulating flow regime is consistent with visual observation reported in the literature. In addition, the developed LM approach can be employed to optimize fuel cell flow field design and operation.

Pressure drop and pressure fluctuations in spouted beds with binary mixtures of particles

Powder Technology

When handling fine particles in spouted beds, addition of coarse particles has shown improved spouting stability than single particle systems. However, segregation may still occur because of insufficient mixing in binary mixtures, which will adversely influence the process performance. Therefore, in this study, analysis of pressure drop and its fluctuation signals were for the first time used to understand mechanisms of flow regime transitions in spouted beds with binary mixtures. The results showed that the typical varying sequence of pressure drop can be observed for spouted bed with binary mixtures and the peak pressure drop is related to the mixing degree of particles, which is mainly influenced by the inter-particle forces between fine particles and their counterpart coarse ones. The statistic characteristics of pressure drop time series, i.e., average value, standard deviation and probability distributions, were found to vary for different flow regimes. Therefore, they could be used for the characterization of these flow regimes. The spouting stability of binary mixtures can be reflected by power spectrum analysis; the influences of particles size and density difference on spouting stability were discussed through power spectral analysis.

A Critical Review of Two-phase Flow in Gas Flow Channels of PEM Fuel Cells

Journal of Power Sources, 195 (15) 4531-4553 (2010)

Flow regime transition and hydrodynamics of spouted beds with binary mixtures

Powder Technology

The spouting of fine particles is significantly different from that of coarse particles and a stable spouting can only be obtained under very constrained operating conditions. However, the stability of a spouted bed with fine particles can be effectively improved by addition of coarse particles. In this work, the flow regime transition and hydrodynamics of spouted beds with binary mixtures were experimentally investigated under a broad range of operating parameters. Effects of particle size, density, mixing ratio, gas velocity and nozzle diameter on flow regime transition and minimum spouting velocity in spouted beds were explored. The results show that a moderate increase in the mean particle diameter and density due to addition of coarse particles is beneficial to spouting stability. However, segregation is also observed when adding excess amount of coarse particles, thus leading to decreased spouting stability.

Measurements of Electrostatic Charging of Powder Mixtures in a Free-fall Test Device

Procedia Engineering

Numerical study of liquid coverage in a gas–liquid–solid packed bed

Particuology

In this work, computational fluid dynamics (CFD) simulations using the volume-of-fluid (VOF) model were employed to investigate the effects of liquid properties, liquid and gas flow rates, and wettability of particles on liquid maldistribution at the microscopic level in a fixed bed reactor. The simulation results show that the number of wetted particles decreases with increasing gas velocity, consequently leading to lower liquid–solid contact areas. The radial liquid distribution is greatly enhanced by increasing the liquid flow rate, whereas the time for the liquid to pass through the whole bed is decreased, as expected. Based on simulation results, it was found that the liquid–solid contact area can be increased by using liquids of high viscosities and more wettable particles. However, the flow-through time increases with increasing liquid viscosity. An increase in the gas density showed a minimal impact on the liquid flow-through time, and the liquid density does not impact the radial liquid distribution or the liquid flow time within a range of liquid densities typically encountered in the petrochemical industry.

Triboelectric charging behavior of wood particles during pellet handling processes

Journal of Loss Prevention in the Process Industries

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.

Bifurcation analysis and multiplicity of steady states in a multistage agitated contactor for gas-liquid processes

The Canadian Journal of Chemical Engineering

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors.

Development of two-phase flow regime specific pressure drop models for proton exchange membrane fuel cells

International Journal of Hydrogen Energy

Water is an inevitable byproduct in proton exchange membrane fuel cells that can lead to complex two-phase flow throughout the cell's components, including the flow field channels utilized for gas delivery. A modified Lockhart–Martinelli (LM) approach based on unique water introduction through the gas diffusion layer is used here to predict the gas–liquid pressure drop in these channels by modifying the Chisholm parameter C. This paper exclusively uses experimental data of two-phase flow multipliers from four sources in the literature, all of which are obtained from active fuel cell operation. C does not appear to change strongly as a function of temperature, relative humidity, or air stoichiometry, but does vary significantly with the current density. This is especially true at low current densities (<500 mA cm−2). To capture this behavior, C is defined as a flow regime dependent parameter based on a flow regime map from the active fuel cell data. In addition to the traditionally used slug, film, and single-phase regimes, an ‘accumulating’ flow regime is proposed to capture the behavior of C and two-phase flow multipliers at low current densities. The proposed accumulating flow regime is consistent with visual observation reported in the literature. In addition, the developed LM approach can be employed to optimize fuel cell flow field design and operation.

Pressure drop and pressure fluctuations in spouted beds with binary mixtures of particles

Powder Technology

When handling fine particles in spouted beds, addition of coarse particles has shown improved spouting stability than single particle systems. However, segregation may still occur because of insufficient mixing in binary mixtures, which will adversely influence the process performance. Therefore, in this study, analysis of pressure drop and its fluctuation signals were for the first time used to understand mechanisms of flow regime transitions in spouted beds with binary mixtures. The results showed that the typical varying sequence of pressure drop can be observed for spouted bed with binary mixtures and the peak pressure drop is related to the mixing degree of particles, which is mainly influenced by the inter-particle forces between fine particles and their counterpart coarse ones. The statistic characteristics of pressure drop time series, i.e., average value, standard deviation and probability distributions, were found to vary for different flow regimes. Therefore, they could be used for the characterization of these flow regimes. The spouting stability of binary mixtures can be reflected by power spectrum analysis; the influences of particles size and density difference on spouting stability were discussed through power spectral analysis.

A Critical Review of Two-phase Flow in Gas Flow Channels of PEM Fuel Cells

Journal of Power Sources, 195 (15) 4531-4553 (2010)

Flow regime transition and hydrodynamics of spouted beds with binary mixtures

Powder Technology

The spouting of fine particles is significantly different from that of coarse particles and a stable spouting can only be obtained under very constrained operating conditions. However, the stability of a spouted bed with fine particles can be effectively improved by addition of coarse particles. In this work, the flow regime transition and hydrodynamics of spouted beds with binary mixtures were experimentally investigated under a broad range of operating parameters. Effects of particle size, density, mixing ratio, gas velocity and nozzle diameter on flow regime transition and minimum spouting velocity in spouted beds were explored. The results show that a moderate increase in the mean particle diameter and density due to addition of coarse particles is beneficial to spouting stability. However, segregation is also observed when adding excess amount of coarse particles, thus leading to decreased spouting stability.

Experimental and statistical analysis of the void size distribution and pressure drop validations in packed beds

Chemical Engineering Research and Design

The void size distribution inside a packed bed is one of the most important parameters affecting the reactor performance. The non-uniform distribution of material and energy flows can be avoided by a reasonable arrangement of the void size distribution. In this work, the void size distributions in a packed bed with structured and random packing were investigated through both theoretical calculations and statistical analysis of experimental results to characterize the bed voids between the particles. In theoretical analysis, the equivalent diameters of voids at different two-dimensional layers in a packed bed with three types of structured packing were first calculated, and then the wax replacement method was adopted to measure the voids inside a randomly packed bed. Different two-dimensional layers of the bed were sliced and photographed for further analysis. The effects of particle size, shape, and packing method were investigated, and the results showed that the relative void size (void size/particle size) was not affected by the particle size. In contrast, the particle shape, which can be represented by particle sphericity, significantly affected the void size distribution. A more flat void size distribution curve was obtained for particles with sphericity close to unity. A new correlation was established based on statistical analysis of the experimental data to account for the void size distribution. This new correlation was validated by predicting the pressure drop of a packed bed and the results of comparison showed good agreement with experimental results.