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Unregistered
02-13-2006, 02:13 PM
I need help can anyone help me convert 250cfm to lbs of ait assuming the temp is 70 deg.F

Robert Fogt
02-14-2006, 10:55 PM
I have the data for dry air at 20º C, which is 1.225 kg/m³. This is only about 68º F, but it is as close as I could find, and should provide a fairly accurate estimate.

1 ft³ = 0.0764741882572885 pounds

250 * 0.0764741882572885 = 19.118547064322125

250 CFM is about 19.11 pounds/minute

Unregistered
05-15-2006, 09:13 PM
i had originally had a much larger explanation with calculations but my computer turned off right as i finished.
any ways, use the percent composition of the different gasses in "air" to find what one mole of "air" weighs. which turns out to be 28.9701 g/mol.

use the equation V= [nRT]/P (where V=volume, n= # of moles, R= 0.08206, T=temp in kelvin and P=pressure in atm(which i assumed to be 1)) to find the volume of one mole of gas at 70 degrees (294.261 kelvin) which is equal to 24.1471 L

250cfm = 7079.21 L/min

divide that by 24.1471 to get moles per minute = 293.1703 mol/minute

multiply that by 28.9701 g/mol to get grams per minute = 8493.1718

divide this by 28.35 to get ounces per minute
and divide again by 16 to get pounds per minute

in the end you get 18.7239 pounds per minute

Ron Ogan
07-02-2007, 10:36 AM