General Gas Law
Compressed Air Theory Volume-flow conversion between two pressure & temperature states
An interactive recreation of a classic compressed-air reference sheet. All figures follow the ideal-gas model with absolute temperature T = 273 + t °C.
01
Volumetric flow — three references
Free air delivery (FAD)
m3/min · l/s
Compressor capacity expressed as free-air volume at intake (atmospheric) conditions.
Air delivery
m3/min · l/s
Volume actually delivered at the compressor outlet, in the compressed state. (1 m3/min = 1000/60 ≈ 16.67 l/s)
Normal flow
m3/min
Volume referred to a fixed datum — 0 °C and 1.013 bar(a) at sea level — i.e. normal m3 (a proxy for mass flow).
02
The general gas law
p·v / T = R (constant) · p·V = m·Rs·T · p·V = n·Ru·T
State variables
p pressure, bar(a)V volume, m3v specific volume, m3/kgT absolute temperature, KQuantity
m mass, kgn amount of gas, kmolM molar mass — air ≈ 28.96 kg/kmolGas constants
Rs = Ru / M
Rs specific = 287.1 J/(kg·K)Ru universal = 8314 J/(kmol·K)Rs = Ru / M
P0·V0 / T0 = Pi·Vi / Ti
valid for a fixed mass of gas · T = 273 + t °C
03
Calculation — air delivery Vi at outlet conditions
Input / reference conditions (0)
l/s
bar(a)
°C
Outlet conditions (i)
bar(a)
°C
Vi / V0 volume ratio
Air delivery Vi
104.76l/s
= 6.285 m³/min
