Find CFM Formula: Pipe Diameter & PSI

  • Thread starter Thread starter shellback
  • Start date Start date
  • Tags Tags
    Cfm Formula
AI Thread Summary
To calculate CFM (cubic feet per minute) for air flow through a pipe, knowing only the pipe diameter and static pressure is insufficient. A differential pressure measurement, such as across an orifice or using a pitot tube, is necessary to determine airflow accurately. The velocity can be calculated using Bernoulli's equation, specifically V=4005*sqrt(Vp), where Vp is the velocity pressure in inches of water gauge. The discussion emphasizes that static pressure alone does not indicate airflow, as it does not account for velocity. Additional details about the setup and pressure measurements are crucial for accurate calculations.
shellback
Messages
3
Reaction score
0
I just want the formula that shows how to find for CFM. I have the pipe diameter and the PSI that are available. I'm just using air, nothing special.
 
Engineering news on Phys.org
shellback said:
I just want the formula that shows how to find for CFM. I have the pipe diameter and the PSI that are available. I'm just using air, nothing special.

Can you be more specific with what you want to know? I presume you mean how to determine the flow rate of air in cubic feet per minute through a pipe when knowing only the pipe diameter and back pressure?

CS
 
stewartcs said:
Can you be more specific with what you want to know? I presume you mean how to determine the flow rate of air in cubic feet per minute through a pipe when knowing only the pipe diameter and back pressure?

CS

Yes, that's exactly right. I know there's a way to do it. I just haven't been able to work that out.
 
The pressure is the static pressure in the pipe? That isn't enough to determine the airflow. You need a differential pressure across an orifice, pressure drop in a venturi or velocity pressure from a pitot tube.

Once you get some form of velocity pressure (and if you give us more details about your setup, we can tell you how to measure/estimate it), you can use a form of Bernoulli's equation to find the velocity:

V=4005*sqrt(Vp)
where
V= velocity in fpm
Vp= velocity pressure in inches of water gauge.
 
Last edited:
russ_watters said:
The pressure is the static pressure in the pipe? That isn't enough to determine the airflow. You need a differential pressure across an orifice, pressure drop in a venturi or velocity pressure from a pitot tube.

We're going to have a compressor maintaining a constant pressure of +100psi regulated to 100psi and a 3/8" ID for the pipe at its' most narrow.
 
That's static pressure. It doesn't have anything directly to do with velocity (consider an air tank pressurized to 100psi: no airflow at all). What is this pipe supplying? Or is it open ended?
 
Thread 'I need a concave mirror with a focal length length of 150 feet'
I need to cut down a 3 year old dead tree from top down so tree causes no damage with small pieces falling. I need a mirror with a focal length of 150 ft. 12" diameter to 36" diameter will work good but I can't think of any easy way to build it. Nothing like this for sale on Ebay. I have a 30" Fresnel lens that I use to burn stumps it works great. Tree service wants $2000.
Hi all, i have some questions about the tesla turbine: is a tesla turbine more efficient than a steam engine or a stirling engine ? about the discs of the tesla turbine warping because of the high speed rotations; does running the engine on a lower speed solve that or will the discs warp anyway after time ? what is the difference in efficiency between the tesla turbine running at high speed and running it at a lower speed ( as fast as possible but low enough to not warp de discs) and: i...
Back
Top