battery Model description

Proton exchange membrane fuel cell thermal field simulation, mainly through the application of basic physical laws, transmission mechanism, the electrochemical theory of the internal battery to simulate complex physical phenomena, and to visualize the simulation results,dell laptop battery increase the proton exchange membrane thermal field distribution inside the fuel cell to understand, effectively guide the PEMFC thermal management, thus improving battery performance.

1.1 Geometry

PEMFC geometry, such as 1, (a) three-dimensional diagram, the body is equivalent to the interception of the actual flow of a single cell, only in the number of different flow channel, its components, including collector plates, flow, diffusion layer, catalyst layer, proton exchange membrane; the flow channel length of 50mm. 1 (b) for the profile structure dimensions, the current collector plate thickness of 2mm, the flow channel size of 1mm × 1mm, the cathode, the anode diffusion layer thickness is 0.2mm, the thickness of the catalyst layer is 0.005mm,dell Inspiron 4000 battery, dell Inspiron 4100 battery, dell Inspiron 2500 battery, dell Latitude CPX battery, dell Latitude C600 battery, dell Latitude C610 battery, dell Latitude C640 battery, proton exchange membrane thickness of 0.05mm, the catalyst layer and proton exchange membrane of total thickness of 0.06mm.

1.2 Mathematical model

1.2.1 Continuity equation

The assumption of continuous medium and low fluid flow conditions, the continuity equation is: where: on the left the first non-steady-state items, the second for the convective terms on the left, the right term for the mass source. Followed by density, porosity, velocity vector, the quality of the source term, which depending on the calculation of Sm domains, solve them separately. Current according to Faraday's Theorem and the introduction of the relationship between the reaction gas consumption, the quality of the source term derived formula to solve for the molar mass, respectively, the Faraday constant, current density,dell Inspiron 4000 battery, water phase change rate, voltage; subscript letters for the component or electrode, H2, O2 , H2O, a, c as hydrogen, oxygen, water, anode and cathode.

1.2.2 Momentum equation

For Newtonian fluid, considering the shear stress and normal stress, the application of Stokes law of viscosity introduced in the form of the momentum equation: the first non-steady-state entry on the left, second left for the convection term; right of the first and second Items for the diffusion term, the right third of the momentum source term. In which p, $, Su was pressure, viscosity, porosity, the momentum source term.

1.2.3 Energy equation

The role of viscous dissipation can be ignored for the steady state of low flow, energy equation can be expressed in: left the first non-steady-state items, the left second to convection; the first term of diffusion, the second term for the energy source term. Which, cp, T, respectively, the specific heat at constant pressure and temperature.

keff is the effective thermal conductivity, namely:

keff = kf + (1 -) ks

Where: subscripts f, s denote fluid and solid; SQ as the energy source term S is the production rate of water vapor; rw for water phase change rate; Sa, c, respectively for the anode and cathode exchange current density; ( for the activation overpotential and concentration overpotential of the total; h is enthalpy; reaction, L, respectively, chemical reactions, phase transitions.

1.2.4 components of equation

When it comes to mixing and chemical reactions, instead of the continuity equation from the equation components, dell Inspiron 4100 battery, namely: where: the first non-steady-state entry on the left; left the second for the convection term; the first term is the diffusion term; right-hand side two diffusion source term. Which, ck,), Sk, respectively, component concentration, porosity and composition of the source term; subscript k for the component code in the cathode, respectively, oxygen, nitrogen and water.

D is the effective diffusion coefficient, which is: Where: Dk,, b, s for the free diffusion coefficient of component k, the curvature of the hole porous medium, the correction factor and liquid water saturation.

1.2.5 Electrochemical model of PEMFC electrochemical reaction exchange current density through the Butler-Volmer equations, namely: the anode-cathode type, considering the reaction gas concentration, temperature, polarization of the electrochemical reaction. Where: The overpotential; Jref reference exchange current density; C, C, C, C are the molar concentrations of hydrogen and references to local molar concentration, molar concentration of oxygen in the local and reference molar concentration; for the concentration index; - for the transfer coefficient; subscript letters a, c, respectively, the anode and cathode.

Proton exchange membrane fuel cells based on the existence of the electric potential in the form of artificially defined as the solid phase potential and the membrane phase potential, called the dual potential. According to charge conservation principle, the current conservation equation is:

△ (e △ / e) + Se = 0

△ (0mem △ 1mem) + Smem = 0

Where: 2 for the local electric potential; S as a current source term,dell Inspiron 4000 battery, dell Inspiron 4100 battery, dell Inspiron 2500 battery, dell Latitude CPX battery, dell Latitude C600 battery, dell Latitude C610 battery, dell Latitude C640 battery, which only exists in the catalyst layer of the electrochemical reaction zone, and Smem + Se = 0; 3 for the electrical conductivity; subscript letters e, mem, respectively, electronic and film. Current source term in the anode and cathode there are some differences. In the anode, Se =- Sa <0, Smem = + Sa> 0; in the cathode Se = Sc> 0, Sm =- Sc 0.

Electrode potential, as well as over two-potential electric potential exists between certain relationship,dell Inspiron 2500 battery, such as shown in eq. Its expression in the anode and cathode are the same, but the value of Vref is different, the anode, Vref = 0; in the cathode, V = Vopen.