The compression ratio of free air to compressed air
Free air is air at ambient conditions at a specific location where
- ambient temperature
- moisture content
- barometric pressure
Compression Ratio is the ratio between Discharge Pressure Absolute and Suction Pressure Absolute.
The compression ratio of free air - to compressed air, is indicated in the diagram below.
Compression Ratio - Pressure (psi)
- 1 psi = 6.9 kPa = 0.069 bar
- 1 ncfm = 0.5 nl/s
Example - Converting a Compressed Air Volume to a Free Air Volume
A compressed air volume flow of 10 acfm at 100 psig must be multiplied with compression ratio approx. 8 to estimate the free air at atmospheric pressure.
- in this case approx. 80 scfm
Compression Ratio - Pressure (bar)