The latent heat fraction is calculated by multiplying the fraction condensed by the moisture content factor (0.00935) and the latent heat of vaporization of water (1087 Btu/lb), then converting to a percentage by dividing by 100. The moisture content factor 0.00935 represents the typical water vapor content per unit fuel combusted, and 1087 Btu/lb is the approximate latent heat of vaporization at typical flue gas dewpoint conditions.

\begin{equation}\label{eq:air-water-cooling-flue-latent-heat-fraction} f_{latent} = \frac{f_{cond} \cdot 0.00935 \cdot 1087}{100}\end{equation}

Symbols

\(f_{latent}\)	Latent heat fraction \([\unit{ \unitless}]\)
\(f_{cond}\)	Fraction of water vapor condensed \([\unit{ \unitless}]\)
\(0.00935\)	Moisture content factor (typical water vapor per fuel unit) \([\unit{ \pound\per\pound}]\)
\(1087\)	Latent heat of vaporization at dewpoint \([\unit{ \btu\per\pound}]\)

Note

The constant 1087 Btu/lb is the latent heat of vaporization of water at typical flue gas dewpoint temperatures (approximately 140°F).