View Full Version : conversion help

04-09-2003, 06:23 AM
How do I convert cubic feet per minute, (cfm,) to pounds per minute,(lb/min.)?



04-09-2003, 08:18 AM
That depends what flow you're trying to measure... air, right?

Air density at STP = 1.29 g/L = 0.0805 lb/cf

so 1 cfm = 0.0805 lb/min for air at STP (standard temp and pressure).

At different temperatures and pressures the density will change.

04-09-2003, 01:57 PM
Thanks for the info!

You were right on your guess of airflow. Basically, what I'm trying to do is work my way through the caculations in Maximum Boost on sizing a compressor. I've got the charts off of Turbonetics site, and I've done the math from the book, but I couldn't figure out how to convert the flow from cfm, (what the book gives,) and lb/min that is on the Turbonetics charts.

So, would the caculation that you provided work for this? In the book it gives a chart, (Table 3-1 if you have the book,) but that numbers seem to not add up, giving me like 390 lf/min based off of a cfm of 392.13 at 2000 feet of elevation.

I'm dying here! I've been figuring these all day from the numbers I came up with, and every compressor's surge point is lying way to the left of the surge line. Somethings not right!


*math-challenged, in case you couldn't tell...*