Definition of SCFM
Definition of SCFM
(OP)
Hello,
Does anyone know if there is a widely accepted spec that defines air properties at 'standard' conditions? I'd like to convert measured CFM to SCFM but I've seen SCFM defined a few ways:
- pressure is usually 1 atmosphere (14.696 psia)
- humidity is usually 0%, or not specified (one source mentioned 60%)
- temperature is sometimes 60F, sometimes 68F, sometimes 25C
Thanks!
Does anyone know if there is a widely accepted spec that defines air properties at 'standard' conditions? I'd like to convert measured CFM to SCFM but I've seen SCFM defined a few ways:
- pressure is usually 1 atmosphere (14.696 psia)
- humidity is usually 0%, or not specified (one source mentioned 60%)
- temperature is sometimes 60F, sometimes 68F, sometimes 25C
Thanks!
ko (www.ecooling.biz)





RE: Definition of SCFM
You can visit the following links for various views.
thread798-106556
thread124-95060
thread135-97506
thread378-90884
thread378-97454
Regards,
RE: Definition of SCFM
ko (www.ecooling.biz)
RE: Definition of SCFM
RE: Definition of SCFM
In Fan Engineering the combinations used for standard air are:
U.S. SI
Dry air
Humidity 0% 0%
Pressure 29.921 in Hg 101.325 kPa
Temperature 70oF 21oC
Density 0.075 lbm/ft3 1.2 kg/m3
Moist air
Humidity 50% 50%
Pressure 29.921 in Hg 101.325 kPa
Temperature 68oF 20oC
Density 0.075 lbm/ft3 1.2 kg/m3
RE: Definition of SCFM
There are many definitions of standard conditions that have been used in the USA for a standard cubic foot of gas. And then there are even more definitions of standard conditions used in the metric world.
It is also true (as already pointed out by others in this thread) that this question has been raised and discussed many, many times in Eng-Tips.
In the USA, the most common definition is the one widely used in the oil and gas industries, namely 60 degrees F and 14.696 psia. At those conditions, 1 pound-mol of any ideal gas equals 379.48 scf.
But since there are other definitions, one should always state the reference conditions of temperature and pressure when using the term scf.
Milton Beychok
(Contact me at www.air-dispersion.com)
.
RE: Definition of SCFM
Actual pound-molal volumes of real gases after correction for Gas Law deviation show almost negligible differences from the 379.48 scf quoted by mbeychock. These may be significant, however, when measurements involve moneys.
Some molar volumes at the standard conditions stated by mbeychock, are:
Oxygen 379.19
Nitrogen 379.38
Hydrogen 379.72
Methane 378.74
Ethane 376.29
Ethylene 377.08
Propane 372.69
n-Butane 366.66
Carbon dioxide 377.35
Sulfur dioxide 372.12
Ammonia 374.92
RE: Definition of SCFM
Thanks
katmar
RE: Definition of SCFM
The data can be obtained from
by looking at fluid properties.