$A_{\mathrm{c}}$	Cross-section area, ${\mathrm{m}}^2$
$C_{\mathrm{p}}$	Molar heat capacity, $\mathrm{J}\cdot {\mathrm{mol}}^{-1}\cdot {\mathrm{K}}^{-1}$
D	Diameter, m
$N_{\mathrm{sum}}$	Molar flow rate, $\mathrm{mol}\cdot {\mathrm{s}}^{-1}$
K p	Equilibrium constant
$L$	Length, $m$
$M$	Molar mass, ${\mathrm{kg}·\mathrm{mol}}^{-1}$
$\mathrm{Pr}$	Prandtl number
$p$	Reaction pressure, Pa
$R$	Universal gas constant, ${\mathrm{J}·\mathrm{mol}·\mathrm{K}}^{-1}$
$R_i$	Molar fraction of component i
$\mathrm{Re}$	Reynolds number
$r$	Chemical reaction rate, ${\mathrm{mol}·\mathrm{s}}^{-1}$
S G	Entropy generation rate, ${\mathrm{J}·\mathrm{K}}^{-1}{·\mathrm{mol}}^{-1}$
$T$	Temperature, K
$\alpha$	Activity coefficient of partial pressure
$\epsilon$	Porosity
$\mu$	Dynamic viscosity, ${\mathrm{kg}·\mathrm{m}}^{-1}{·\mathrm{s}}^{-1}$
$\sigma$	Local entropy generate rate, ${\mathrm{J}·\mathrm{K}}^{-1}{·\mathrm{m}}^{-1}{·\mathrm{s}}^{-1}$
$\rho$	Density, $\mathrm{kg}\cdot {\mathrm{m}}^{-3}$
$\lambda$	Covariate variable vector
$\gamma$	activity coefficient
$\Delta G$	Gibbs free energy change of reaction, ${\mathrm{J}·\mathrm{mol}}^{-1}$
$\Delta H$	Enthalpy of reaction, ${\mathrm{J}·\mathrm{mol}}^{-1}$
AP	Ammonia production rate
AF	Exit ammonia molar fraction
ER	Total exothermic rate