Runtime depends on storage volume, atmospheric pressure, airflow demand, and the pressure band between full-load and unload pressure. Blowdown runtime is limited by the configured blowdown time.

\begin{equation}\label{eq:load-unload-unload-runtime} t_{unload} = \frac{V_s \cdot 60(P_{UL} - P_{FL})}{Q \cdot P_{atm}} \end{equation}

\begin{equation}\label{eq:load-unload-blowdown-runtime} t_{bd} = \min(t_{bd,set}, t_{unload}) \end{equation}

\begin{equation}\label{eq:load-unload-decay-time} \tau_{bd} = \frac{t_{bd,set}}{\ln(1/\epsilon)} \end{equation}

Symbols

\(t_{unload}\)	Time available during unloaded decay \([\unit{ \second}]\)
\(V_s\)	Receiver storage volume \([\unit{ \cubicFoot}]\)
\(P_{UL}\)	Unload pressure \([\unit{ \psig}]\)
\(P_{FL}\)	Full-load pressure \([\unit{ \psig}]\)
\(Q\)	Airflow demand represented by the curve point \([\unit{ \acfm}]\)
\(P_{atm}\)	Atmospheric pressure \([\unit{ \psia}]\)
\(t_{bd,set}\)	Configured blowdown time \([\unit{ \second}]\)
\(\tau_{bd}\)	Blowdown exponential decay time constant \([\unit{ \second}]\)
\(\epsilon\)	Legacy decay tolerance (0.02) \([\unit{ \unitless}]\)