The feedwater mass flow rate is calculated by adding the blowdown fraction to the steam mass flow. Blowdown is the water deliberately discharged from the boiler to control dissolved solids concentration.

\begin{equation}\label{eq:water-heating-flue-feedwater-mass-flow} \dot{m}_{fw} = \dot{m}_{steam} \cdot (1 + BD)\end{equation}

Symbols

\(\dot{m}_{fw}\)	Feedwater mass flow rate \([\unit{ \kilogram\per\hour}]\)
\(\dot{m}_{steam}\)	Steam mass flow rate \([\unit{ \kilogram\per\hour}]\)
\(BD\)	Blowdown percentage (fraction) \([\unit{ \unitless}]\)