The available heat is adjusted from the standard available heat to account for the benefits of oxygen enrichment. Enriching the combustion air with oxygen reduces the nitrogen content, which decreases sensible heat losses in the flue gas. The correction is proportional to the oxygen enrichment level, flue gas temperature, and the difference from ambient conditions.

\begin{equation}\label{eq:o2-enrichment-available-heat} AH = AH_{std} + 100 \cdot k_O \cdot \frac{O_{2,air} - 0.21}{O_{2,air}} \cdot 0.02 \cdot \frac{T_{flue} - 60}{980}\end{equation}

Symbols

\(AH\)	Available heat with enrichment \([\unit{ \percent}]\)
\(AH_{std}\)	Standard available heat \([\unit{ \percent}]\)
\(k_O\)	Oxygen enrichment factor (9.38) \([\unit{ \unitless}]\)
\(O_{2,air}\)	Oxygen in combustion air \([\unit{ \unitless}]\)
\(0.21\)	Reference oxygen fraction in air \([\unit{ \unitless}]\)
\(0.02\)	Available heat fraction factor \([\unit{ \unitless}]\)
\(T_{flue}\)	Flue gas temperature \([\unit{ \degreeFahrenheit}]\)
\(60\)	Ambient reference temperature \([\unit{ \degreeFahrenheit}]\)
\(980\)	Available heat temperature divisor \([\unit{ \degreeFahrenheit}]\)
\(100\)	Conversion factor to percentage \([\unit{ \unitless}]\)