Isothermal receiver free-air rate calculator

This ideal isothermal drawdown balance estimates average free-air use, without a leakage-pressure correction.

Units

Q_{\text{free}} = \frac{V \times \left(P_{1} - P_{2}\right)}{P_{\text{atm}} \times t}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

Q_{\text{free}} = \frac{120 \times \left(105 - 85\right)}{14.7 \times 2} \approx 81.633

Symbol	Meaning	Unit
$Q_{\text{free}}$	average free-air withdrawal	cfm
$V$	connected tank and piping volume	ft³
$P_{1}$	initial gauge pressure	psig
$P_{2}$	final gauge pressure	psig
$P_{\text{atm}}$	site atmospheric pressure	psia
$t$	withdrawal duration	min

Symbol	Meaning	Unit
$Q_{\text{free}}$	average free-air withdrawal	L/s
$V$	connected tank and piping volume	L
$P_{1}$	initial gauge pressure	kPa(g)
$P_{2}$	final gauge pressure	kPa(g)
$P_{\text{atm}}$	site atmospheric pressure	kPa(a)
$t$	withdrawal duration	s

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.