.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)

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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