Definition of SCFM

[ko99]

Hello,

Can anyone tell me the parameters used to determine SCFM? I've seen SCFM conditions described a few different ways:
- pressure is usually 1 atmosphere (14.696 psia)
- humidity is usually 0%, or not specified
- temperature is sometimes 60F, sometimes 68F, sometimes 25C

Does ASHRAE specify this? If not, can you recommend another widely accepted standard?

Thankyou





ko (

http://www.ecooling.biz)

 

[mbeychok]

ko99:

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.

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)
.

 

[25362]

It appears that AGA uses as standard conditions 60^oF and 30 inches (762 mm) of mercury.

In fan engineering (Buffalo Forge Company) U.S. units for standard air are:

Dry air: 29.921 in. Hg; 70^oF; humidity 0%; density 0.075 lb_m/ft³.

Moist air: 29.921 in. Hg; 68^oF; humidity 50%; density 0.075 lb_m/ft³.

Various other combinations are used in other fields of engineering, thus values for STP should always be specified. If the gas is not air, then the standard gas also should be specified.