Use this method when a compressor can partially replenish the storage volume during the demand event through a controlled recovery flow. In many compressed air systems this recovery flow is regulated by a needle valve that meters air into or out of the storage receiver at a slower fixed rate \(Q_{metered}\). The calculator accounts for both the stored air and the metered recovery flow available during the event: only the net demand \((Q_{flow} - Q_{metered})\) draws from the stored volume, often reducing the required tank size compared to a storage-only design. This method is appropriate for intermittent, high-flow applications where a controlled refill rate is desired.

\begin{equation}\label{eq:receiver-tank-metered-storage-size} V_{required} = \frac{k_{gal} \cdot t_{demand} \cdot (Q_{flow} - Q_{metered}) \cdot P_{atm}}{P_{in} - P_{out}} \end{equation}

Symbols

\(V_{required}\)	Required receiver tank size \([\unit{ \gallon}]\)
\(k_{gal}\)	Gallons per cubic foot (7.48) \([\unit{ \gallon\per\cubicFoot}]\)
\(t_{demand}\)	Duration of the air demand event \([\unit{ \minute}]\)
\(Q_{flow}\)	Required air flow rate during the demand event \([\unit{ \cubicFoot\per\minute}]\)
\(Q_{metered}\)	Metering valve (needle valve) flow rate \([\unit{ \cubicFoot\per\minute}]\)
\(P_{atm}\)	Atmospheric pressure \([\unit{ \psi}]\)
\(P_{in}\)	Initial tank pressure \([\unit{ \psi}]\)
\(P_{out}\)	Final tank pressure \([\unit{ \psi}]\)