.FuelCellLib.Basics.tp_act

Information

tp_act-Transport Phenomena


The following eq, shows the flux of gases depending of two phenomena: Stefan-Maxwell diffusion, and Knudsen diffusion.

The following eqs., shows the expression of binary diffusion coeffient and Knudsen diffusion coefficient equations. This is variable modeling hypothesis, and it could be simulated as a constant or a dependence on pore size equation.

This equation shown the flux of liquid water like a dependence on the gradient of water load and electrosmotic drag. In the library , the electrosmotic drag is a opcional modeling hypothesis, selected by the parameter "ModHyp3" in active layer (ACT_LAYER) located in LAYER1D package.

Electrosmotic drag coefficient is a empirical equation, this depends on the water load of the electrolyte and the lectrolyte pore. This coefficient shows the water flux and protonic flux ratio.

The electronic current is shown as a ohm?s law

The maximum water load in active layer is shown next and it depends on the density of water and the membrane and the volume of electrolyte.

The pore volume is the blank space that doesn't fill the electrolyte, liquid water and solid volume.

Protonic flux depends on the gradient of electrolyte voltage multiply by the protonic conductivity and the electrolyte volume.

In the library the proton conductivity is another variable modeling hypothesis, called "ModHyp4" located in "ACT_LAYER" in the Layers1D package. The user select with "ModHyp4" a constant proton conductivity or a water load dependence equation of proton conductivity.

Parameters

Name Default Description
tau   Tortuosity
Es   Volumetric fraction of the solid
Ee   Volumetric fraction of the electrolyte
da   Thickness of transport phenomena [m]
T   Operation temperature [K]
Dwl   Surface diffusion coefficient of H2O, liquid phase [m2/s]
ks   Electrical conducivity of the solid [S/m]
rom   Density of the electrolyte [kg/m3]
ros   Density of the solid [kg/m3]
kpo   Constant protonic conducivity of the electrolyte [S/m]
roh2ol   Density of water [kg/m3]
posat   Reference Saturation pressure [Pa]
Tosat   Reference Saturation temperature [K]
D1co   Constant Knudsen diffusion coefficient for oxygen [m2/s]
D2co   Constant Knudsen diffusion coefficient for steam water [m2/s]
rp   Pore size of porous media [m]
D12o   Constant binary diffusion coefficient [m2/s]
pAref   Reference pressure to measure the binary diffusion coefficient [Pa]
Tref   Reference temperature to measure the binary diffusion coefficient [K]
Mm   Molecular mass of the membrane [kg/mol]
ModHyp2   Knudsen diffusion pore size dependence(0:Off,1:On)
ModHyp3   Electro-Osmotic drag effect(0:Off,1:On)
ModHyp4   Electrolyte conductivity dependence(0:Off,1:On)


References


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