![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
ABSTRACT
In this work, a three-dimensional, non-isothermal, steady-state model for high temperature proton exchange membrane fuel cells with phosphoric acid polybenzimidazole membrane has been developed using computational fluid dynamics. The importance of the gas flow field design on the transport characteristics and cell performance is revealed by solving the mass, momentum, species, energy, and charge conservation equations. The numerical results show that the best cell performance is provided by the fuel cell with serpentine flow channel flow field. However, the pressure drop is also very high due to the large length of the serpentine channel. In addition, the velocity, oxygen mass fraction, and temperature distributions are unevenly distributed over the entire active area of the fuel cell having straight channels with small manifolds, especially at low cell voltages when a large amount of oxygen is required. The cell performance and durability can be significantly affected by the uniformity of the reactants within the fuel cell. It is suggested that the flow field configurations must be optimized to obtain uniform distributions of the reactants, maximize the cell performance, and minimize the pressure drop penalty. The present results provide detailed information about transport characteristics within fuel cells and give guidelines for design and manufacturing of current collectors.
Nomenclature
| a | = | effective surface area, m−1 |
| A | = | active area, m2 |
| c | = | mole concentration, mol m−3 |
| cp | = | specific heat, J kg1 K−1 |
| D | = | diffusivity, m2 s−1 |
| DL | = | doping level |
| F | = | Faraday constant, 96,485 C mol−1 |
| i | = | exchange current density, A m−2 |
| I | = | current density, A m−2 |
| j | = | volumetric current density, A m−3 |
| k | = | thermal conductivity, W m−1 K−1 |
| K | = | permeability, m2 |
| L | = | volume fraction |
| M | = | molecular weight, kg mol−1 |
| P | = | pressure, Pa |
| Q | = | mass flow rate, kg s−1 |
| R | = | universal gas constant, 8.314 J mol−1 K−1 |
| S | = | source term |
| T | = | temperature, K |
| = | velocity vector, m/s | |
| U | = | thermodynamic equilibrium potential, V |
| V | = | voltage, V |
| X | = | mole fraction |
| Y | = | mass fraction |
| Greek symbols | = | |
| α | = | transfer coefficient |
| ε | = | porosity |
| η | = | over-potential, V |
| μ | = | dynamic viscosity, Pa s |
| ξ | = | stoichiometric ratio |
| ρ | = | density, kg m−3 |
| σ | = | electron/proton conductivity, S m−1 |
| ϕ | = | potential, V |
| Superscripts and subscripts | = | |
| a | = | anode |
| c | = | cathode |
| CL | = | catalyst layer |
| eff | = | effective |
| f | = | fluid |
| g | = | gas |
| GDL | = | gas diffusion layer |
| i | = | ith species |
| m | = | membrane/mixture |
| mass | = | mass equation |
| mom | = | momentum equation |
| ref | = | reference |
| s | = | solid |
| T | = | temperature equation |
Nomenclature
| a | = | effective surface area, m−1 |
| A | = | active area, m2 |
| c | = | mole concentration, mol m−3 |
| cp | = | specific heat, J kg1 K−1 |
| D | = | diffusivity, m2 s−1 |
| DL | = | doping level |
| F | = | Faraday constant, 96,485 C mol−1 |
| i | = | exchange current density, A m−2 |
| I | = | current density, A m−2 |
| j | = | volumetric current density, A m−3 |
| k | = | thermal conductivity, W m−1 K−1 |
| K | = | permeability, m2 |
| L | = | volume fraction |
| M | = | molecular weight, kg mol−1 |
| P | = | pressure, Pa |
| Q | = | mass flow rate, kg s−1 |
| R | = | universal gas constant, 8.314 J mol−1 K−1 |
| S | = | source term |
| T | = | temperature, K |
| = | velocity vector, m/s | |
| U | = | thermodynamic equilibrium potential, V |
| V | = | voltage, V |
| X | = | mole fraction |
| Y | = | mass fraction |
| Greek symbols | = | |
| α | = | transfer coefficient |
| ε | = | porosity |
| η | = | over-potential, V |
| μ | = | dynamic viscosity, Pa s |
| ξ | = | stoichiometric ratio |
| ρ | = | density, kg m−3 |
| σ | = | electron/proton conductivity, S m−1 |
| ϕ | = | potential, V |
| Superscripts and subscripts | = | |
| a | = | anode |
| c | = | cathode |
| CL | = | catalyst layer |
| eff | = | effective |
| f | = | fluid |
| g | = | gas |
| GDL | = | gas diffusion layer |
| i | = | ith species |
| m | = | membrane/mixture |
| mass | = | mass equation |
| mom | = | momentum equation |
| ref | = | reference |
| s | = | solid |
| T | = | temperature equation |
Acknowledgment
This work was carried out at the Department of Energy Sciences, Lund University.