Air flow in a pipe

[moodysjAUEE87]

I am looking for an equation to determine air flow (standard) in a frictionless short pipe given diameter and the pressure differential across it. For example a 2.5" diameter pipe of 1 ft length has 20" H20 pressure across it. How much air (cfm) is it flowing? Thanks.

 

[Heckler]

This thread should give you the information needed to for the CFM with a given pressure drop. thread378-152231

Best Regards,

Heckler
Sr. Mechanical Engineer
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[touch84]

the flow of mass is m [kg/s]= rho*u*S
and this is constant in every section (if you are in a stable condition).
rho= density;
u=speed;
S=Area of the section that is constant in this case.

If the pipe is frictionless and the flow is adiabatic the total rho is constant (1.225 kg/m^3) so you can calculate the rho in this way:

rho=total rho*(1+(gamma-1)*M^2/2)^(-1/(gamma-1));
where
gamma=cp/cv=1.4;
M=number of mach;