The mean specific heat of combustion air is approximated using a linear correlation with temperature. This accounts for the temperature-dependent properties of O2, N2, and H2O in the air.

\begin{equation}\label{eq:gas-flue-gas-material-cp-linear-cpp} Cp_{mean} = a + b \cdot T\end{equation}

Symbols

\(Cp_{mean}\)	Mean specific heat of combustion air \([\unit{ \btu\per\pound\degreeFahrenheit}]\)
\(a\)	Linear coefficient (intercept) \([\unit{ \btu\per\pound\degreeFahrenheit}]\)
\(b\)	Linear coefficient (slope) \([\unit{ \btu\per\pound\degreeFahrenheit\squared}]\)
\(T\)	Temperature \([\unit{ \degreeFahrenheit}]\)