Symbols
$a$	Channel width/$\mathrm{m}$
$b$	Channel height/$\mathrm{m}$
$C$	Volumetric molar concentration/${\mathrm{mol} \mathrm{m}}^{-3}$
$c_k$	Concentration of mobile charge carriers k/${\mathrm{mol} \mathrm{m}}^{-3}$
$D_{ik}$	Binary diffusion coefficient of species i into k/${\mathrm{m}}^2{\mathrm{s}}^{-1}$
$D_h$	Hydraulic diameter/$\mathrm{m}$
$D_{Kn}$	Knudsen diffusion coefficient/${\mathrm{m}}^2{\mathrm{s}}^{-1}$
$E_{act}^f$	Activation energy of forward reaction/${\mathrm{kJ} \mathrm{mol}}^{-1}$
$E_{act}^r$	Activation energy of reverse reaction/${\mathrm{kJ} \mathrm{mol}}^{-1}$
$F$	Faraday constant/$\mathrm{96,485.33}{ \mathrm{C} \mathrm{mol}}^{-1}$
$h$	Specific molar enthalpy/${\mathrm{kJ} \mathrm{mol}}^{-1}$
$h_m$	Mass transfer coefficient/${\mathrm{m} \mathrm{s}}^{-1}$
$i_k$	Current density of charge carrier k/${\mathrm{A} \mathrm{m}}^{-2}$
$j_i$	Diffusive molar flux of species i/${\mathrm{mol} \mathrm{s}}^{-1}{ \mathrm{m}}^{-2}$
$k_f$	Forward reaction rate constant/${\mathrm{kmol} \mathrm{m}}^{-2}{\mathrm{s}}^{-1}$
$k_r$	Reverse reaction rate constant/${\mathrm{kmol} \mathrm{m}}^{-2}{\mathrm{s}}^{-1}$
$k_{eq}$	Equilibrium constant of reaction/-
$M_i$	Molecular mass of species i/${\mathrm{kg} \mathrm{kmol}}^{-1}$
$N_i$	Absolute molar flux of species i/${\mathrm{mol} \mathrm{s}}^{-1}{ \mathrm{m}}^{-2}$
$p$	Pressure/$\mathrm{Pa}$
$\dot{Q}$	Thermal power/${\mathrm{kW} \mathrm{m}}^{-3}$
$R$	Universal gas constant/$8314{ \mathrm{J} \mathrm{kmol}}^{-1}{\mathrm{K}}^{-1}$
$r_{pore}$	Average pore radius/$\mathsf{\mu }\mathrm{m}$
$r$	Reaction rate/${\mathrm{mol} \mathrm{s}}^{-1}{ \mathrm{m}}^{-3}$
$Sh$	Sherwood number/-
$T$	Temperature/$\mathrm{K}$
$t$	Support thickness/$\mathrm{mm}$
$x_i$	Molar fraction of species i/-
$v_i$	Velocity/${\mathrm{m} \mathrm{s}}^{-1}$
$z_k$	Number of charge carrier k/-
$z$	Transversal coordinate through supported membrane/-
Greek symbols
${\delta }_m$	Mass diffusion boundary layer/$\mathrm{m}$
$\mathsf{\Delta }{H}_r^{°}$	Standard reaction enthalpy/${\mathrm{kJ} \mathrm{mol}}^{-1}$
$ϵ$	Average porosity/-
$\varphi$	Electrostatic potential/$\mathrm{V}$
${\mu }_k$	Chemical potential of charge carrier k/$\mathrm{V}$
${\nu }_i$	Molecule diffusion volume of species i/-
${\sigma }_k$	Charge carrier k conductivity/${\mathrm{S} \mathrm{m}}^{-1}$
$\tau$	Average tortuosity/-
Acronyms
OTM	Oxygen Transport Membrane
MIEC	Mixed Ionic-Electronic Conductor
ORR	Oxygen Reduction Reaction
TPB	Triple Phase Boundary
DPB	Double Phase Boundary
SFM	Stagnant Film Model
DGM	Dusty Gas Model
SOFC	Solid Oxide Fuel Cells
VSA	Vacuum Swing Adsorption
PSA	Pressure Swing Adsorption
Subscripts/Superscripts
$w$	Membrane wall
$b$	Gas bulk phase
$mix$	Mixture
′	Feed (reduction) side
″	Permeate (oxidation) side
$eff$	Effective property
$Kn$	Knudsen diffusion term