The outlet exhaust temperature is calculated by subtracting the temperature drop in the flue gas from the inlet flue gas temperature. The temperature drop is the ratio of heat recovered to the heat capacity of the flue gas.

\begin{equation}\label{eq:air-heating-exhaust-outlet-temperature} T_{outlet} = T_{flue} - \frac{Q_{recovered}}{C_{flue}}\end{equation}

Symbols

\(T_{outlet}\)	Outlet exhaust temperature \([\unit{ \degreeFahrenheit}]\)
\(T_{flue}\)	Flue gas temperature \([\unit{ \degreeFahrenheit}]\)
\(Q_{recovered}\)	Heat recovered by cold air \([\unit{ \btu\per\hour}]\)
\(C_{flue}\)	Heat capacity of flue gas \([\unit{ \btu\per\degreeFahrenheit}]\)