Calculation of pressure in a pipeline derived from volume flow rate.
Calculation of pressure in a pipeline derived from volume flow rate.
(OP)
Is it possible to derive the pressure of air flowing through a pipeline from the volume flow rate and the diameter of the pipe. For instance pipe I.D. = 150mm and volume flow rate = 0.3m³/sec.
I have looked at Bernoulli's eqn and the continuity eqn and hence come to the conclusion that the pressure is dependant on the input to the line. I have no other data for this query other than I can tell you the media is air and the pipe is situated in a tunnel.
Please help, for I am getting a little bit frustrated.
I have looked at Bernoulli's eqn and the continuity eqn and hence come to the conclusion that the pressure is dependant on the input to the line. I have no other data for this query other than I can tell you the media is air and the pipe is situated in a tunnel.
Please help, for I am getting a little bit frustrated.





RE: Calculation of pressure in a pipeline derived from volume flow rate.
If you get involved in pipe calculations for gases, the following equations may be useful to you.
General Gas flow equation:
Qb= 234.8 (Tb /Pb )(√1/f){(P12- P22)/( G L ZavgTavg)}1/2 D2.5
General Gas flow equation with elevation correction:
Qb= 234.8 (Tb /Pb )(√1/f){(P12- P22 - 0.0375 G dX (Pavg2/ZavgTavg))/( G L ZavgTavg)}1/2 D2.5
Where:
Qb=scfh
Tb=base temp, deg R
Pb=base pressure, psia
√1/f = transmission factor (f= Darcy-Weisbach friction factor)
P1 and P2 = inlet and outlet pressure, psia
D=diameter, inches
G= gravity relative to air
dX=elevation change, feet
Pavg=average pressure, psia
Tavg=average temperature, deg R
L=Length, feet
Zavg=average compressibility
Colebrook (Darcy-Weisbach)
1/√f= -2Log{(ke/3.7D)+(2.51/NRe)1/√f}