scispace - formally typeset
Search or ask a question
Author

Hua Meng

Other affiliations: Pennsylvania State University
Bio: Hua Meng is an academic researcher from Zhejiang University. The author has contributed to research in topics: Heat transfer & Supercritical fluid. The author has an hindex of 30, co-authored 65 publications receiving 2986 citations. Previous affiliations of Hua Meng include Pennsylvania State University.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, a three-dimensional non-isothermal model is developed to account rigorously for various heat generation mechanisms, including irreversible heat due to electrochemical reactions, entropic heat, and Joule heating arising from the electrolyte ionic resistance.

391 citations

Journal ArticleDOI
TL;DR: In this paper, the evolution of a cryogenic fluid jet initially at a subcritical temperature and injected into a supercritical environment, in which both the pressure and temperature exceed the thermodynamic critical state, has been investigated numerically.
Abstract: The evolution of a cryogenic fluid jet initially at a subcritical temperature and injected into a supercritical environment, in which both the pressure and temperature exceed the thermodynamic critical state, has been investigated numerically. The model accommodates full conservation laws and real-fluid thermodynamics and transport phenomena. All of the thermophysical properties are determined directly from fundamental thermodynamics theories, along with the use of the corresponding state principles. Turbulence closure is achieved using a large-eddy-simulation technique. As a specific example, the dynamics of a nitrogen fluid jet is studied systematically over a broad range of ambient pressure. Owing to the differences of fluid states and flow conditions between the jet and surroundings, a string of strong density-gradient regimes is generated around the jet surface and exerts a stabilizing effect on the flow development. The surface layer acts like a solid wall that transfers the turbulent kinetic energy...

220 citations

Journal ArticleDOI
TL;DR: In this paper, a unified treatment of general fluid thermodynamics is developed to handle fluid flows over their entire thermodynamic states, based on the concepts of partial-mass and partial-density properties, and accommodates thermodynamic nonidealities and transport anomalies in the transcritical regime.

211 citations

Journal ArticleDOI
TL;DR: In this article, a three-dimensional, single-phase, isothermal numerical model of polymer electrolyte fuel cell was employed to investigate effects of electron transport through the gas diffusion layer.
Abstract: A three-dimensional, single-phase, isothermal numerical model of polymer electrolyte fuel cell ~PEFC! was employed to investigate effects of electron transport through the gas diffusion layer ~GDL! for the first time. An electron transport equation was additionally solved in the catalyst and gas diffusion layers, as well as in the current collector. It was found that the lateral electronic resistance of GDL, which is affected by the electronic conductivity, GDL thickness, and gas channel width, played a critical role in determining the current distribution and cell performance. Under fully-humidified gas feed in the anode and cathode, both oxygen and lateral electron transport in GDL dictated the current distribution. The lateral electronic resistance dominated the current distribution at high cell voltages, while the oxygen concentration played a more decisive role at low cell voltages. With reduced GDL thickness, the effect of the lateral electronic resistance on the current distribution and cell performance became even stronger, because the cross-sectional area of GDL for lateral electron transport was smaller. Inclusion of GDL electron transport enabled the thickness of GDL and widths of the gas channel and current collecting land to be optimized for better current distribution and cell performance. In addition, the present model enables: ~i! direct incorporation of contact resistances emerging from GDL/catalyzed membrane or GDL/land interface, ~ii! implementation of the total current as a more useful boundary condition than the constant cell voltage, and ~iii! stack modeling with cells connected in series and hence having the identical total current.

209 citations

Journal ArticleDOI
TL;DR: In this article, a mathematical model for two-phase flow and flooding dynamics in polymer electrolyte fuel cells PEFCs is developed based on recent experimental observations, which consists of four submodels to account for two phase phenomena, including a catalyst coverage model in the catalyst layer, a two phase transport model in GDL, a liquid coverage model at the GDL-channel interface, and a twophase flow model in GC.
Abstract: A mathematical model for two-phase flow and flooding dynamics in polymer electrolyte fuel cells PEFCs has been developed based on recent experimental observations. This three-dimensional PEFC model consists of four submodels to account for two-phase phenomena, including a catalyst coverage model in the catalyst layer, a two-phase transport model in the gas diffusion layer GDL, a liquid coverage model at the GDL-channel interface, and a two-phase flow model in the gas channel GC .T he multiphase mixture M 2 model is employed to describe liquid water transport in the GDL while a mist flow model is used in the gas channel. An interfacial coverage model by liquid water at the GDL/GC interface is developed, for the first time, to account for water droplet emergence on the GDL surface. The inclusion of this interfacial model not only gives the present two-phase model a capability to predict the cathode flooding effect on cell performance, but also ultimately removes the inability of prior two-phase models to correctly capture effects of the gas velocity or stoichiometry on cell performance. Water management is a central issue in design and optimization of polymer electrolyte fuel cells PEFCs. There are two wellunderstood reasons: first, the proton conductivity of the electrolyte membrane depends strongly on hydration; second, the presence of excessive liquid water covers catalyst sites in the catalyst layer as well as blocks the oxygen transport in the gas diffusion layer GDL, resulting in substantial concentration polarization. Therefore, a delicate balance of water in the cell must be maintained to ensure proper operation. Because the oxygen reduction reaction ORR in the cathode catalyst layer produces water, prevention of liquid water flooding is especially crucial on the cathode side of the cell.

200 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this article, the authors present the latest status of PEM fuel cell technology development and applications in the transportation, stationary, and portable/micro power generation sectors through an overview of the state-of-the-art and most recent technical progress.

2,687 citations

Journal ArticleDOI
TL;DR: Technical Challenges 4754 4.2.1.
Abstract: 3.8.2. Temperature Distribution Measurements 4749 3.8.3. Two-Phase Visualization 4750 3.8.4. Experimental Validation 4751 3.9. Modeling the Catalyst Layer at Pore Level 4751 3.10. Summary and Outlook 4752 4. Direct Methanol Fuel Cells 4753 4.1. Technical Challenges 4754 4.1.1. Methanol Oxidation Kinetics 4754 4.1.2. Methanol Crossover 4755 4.1.3. Water Management 4755 4.1.4. Heat Management 4756 4.2. DMFC Modeling 4756 4.2.1. Needs for Modeling 4756 4.2.2. DMFC Models 4756 4.3. Experimental Diagnostics 4757 4.4. Model Validation 4758 4.5. Summary and Outlook 4760 5. Solid Oxide Fuel Cells 4760 5.1. SOFC Models 4761 5.2. Summary and Outlook 4762 6. Closing Remarks 4763 7. Acknowledgments 4763 8. References 4763

1,132 citations

Journal ArticleDOI
TL;DR: In this article, the state and transport mechanism of water in different components of PEMFC are elaborated in detail, and the experimental techniques have been developed to predict distributions of water, gas species, temperature and other parameters in polymer electrolyte membrane fuel cell (PEMFC).

717 citations

Journal ArticleDOI
TL;DR: This review has highlighted the important effects that should be modeled and shown the vast complexities of transport within polymer-electrolyte fuel cells and the various ways they have been and can be modeled.
Abstract: In this review, we have examined the different models for polymer-electrolyte fuel cells operating with hydrogen. The major focus has been on transport of the various species within the fuel cell. The different regions of the fuel cell were examined, and their modeling methodologies and equations were elucidated. In particular, the 1-D fuel-cell sandwich was discussed thoroughly because it is the most important part of the fuel-cell assembly. Models that included other effects such as temperature gradients and transport in other directions besides through the fuel-cell sandwich were also discussed. Models were not directly compared to each other; instead they were broken down into their constitutive parts. The reason for this is that validation of the models is usually accomplished by comparison of simulation to experimental polarization data (e.g., Figure 3). However, other data can also be used such as the net flux of water through the membrane. In fitting these data, the models vary not only in their complexity and treatments but also in their number and kind of fitting parameters. This is one reason it is hard to justify one approach over another by just looking at the modeling results. In general, it seems reasonable that the more complex models, which are based on physical arguments and do not contain many fitting parameters, are perhaps closest to reality. Of course, this assumes that they fit the experimental data and observations. This last point has been overlooked in the validation of many models. For example, a model may fit the data very well for certain operating conditions, but if it does not at least predict the correct trend when one of those conditions is changed, then the model is shown to be valid only within a certain operating range. This review has highlighted the important effects that should be modeled. These include two-phase flow of liquid water and gas in the fuel-cell sandwich, a robust membrane model that accounts for the different membrane transport modes, nonisothermal effects, especially in the directions perpendicular to the sandwich, and multidimensional effects such as changing gas composition along the channel, among others. For any model, a balance must be struck between the complexity required to describe the physical reality and the additional costs of such complexity. In other words, while more complex models more accurately describe the physics of the transport processes, they are more computationally costly and may have so many unknown parameters that their results are not as meaningful. Hopefully, this review has shown and broken down for the reader the vast complexities of transport within polymer-electrolyte fuel cells and the various ways they have been and can be modeled.

649 citations

Journal ArticleDOI
TL;DR: A comprehensive review of the lattice Boltzmann (LB) method for thermofluids and energy applications, focusing on multiphase flows, thermal flows and thermal multi-phase flows with phase change, is provided in this paper.

618 citations