flow through 3/4 nps sch 80 steel pipe
flow through 3/4 nps sch 80 steel pipe
(OP)
If a system has 1500 psi upstream pressure with 400 cu ft of compressed air storage (50,000 cubic feet of air available), will the flow through 45 ft of 3/4 nps sch 80 pipe with four (4) elbows be greater than 10,000 scfm with a pressure drop of 900 or more psi?
MY calculation is 11278 cfm, but I have a colleague who says it is only 2700 cfm.
Any help would be appreciated.
MY calculation is 11278 cfm, but I have a colleague who says it is only 2700 cfm.
Any help would be appreciated.
J. Alton Cox
www.delucatest.com





RE: flow through 3/4 nps sch 80 steel pipe
With an exit to atmosphere, I got 269 lb/min. This is about 3330 scfm.
Good luck,
Latexman
RE: flow through 3/4 nps sch 80 steel pipe
J. Alton Cox
www.delucatest.com
RE: flow through 3/4 nps sch 80 steel pipe
With a 2" pipe I get 37000 cfm.
To get 10000 cfm the program predicts a required diameter of 1.16".
It is interesting to note that with a small diameter like 3/4" the calculation is rather sensitive to the pipe roughness you assume. I got 4500 cfm with drawn tubing (e=0.00006") through 3300 cfm for new pipe (e=0.002") to 2500 cfm with "slightly rusty" pipe (e=0.012").
regards
Katmar
RE: flow through 3/4 nps sch 80 steel pipe
I was using 0.051 for roughness factor.
Thanks for the input.
J. Alton Cox
www.delucatest.com
RE: flow through 3/4 nps sch 80 steel pipe
RE: flow through 3/4 nps sch 80 steel pipe
Good luck,
Latexman
RE: flow through 3/4 nps sch 80 steel pipe
J. Alton Cox
www.delucatest.com
RE: flow through 3/4 nps sch 80 steel pipe
G=mass flux flow per unit area
V=specific volume
P= pressure
f= moody friction factor (mean value over the flow length)
L= equivalent length of pipe
D= pipe inside diameter
gamma= ratio of Cp/Cv
Subscripts
0 source stagnation conditions
1 pipe entrance conditions
Conservation of mass, energy and momentum yield after integration of differential equations
G^2(gamma+1)/gamma *ln (V/V1) + PoVo(1/V^2-1/V1^2) +G^2fL/D =0
For a known flow rate and fL/D calcualte V
Pressure is obtained from energy equation
P=PoVo/V - (gamma-1)/2/gamma *(GV)^2
As an approximation use V1=V0
NOTE flow is choked if
(GV)= sqrt[2PoVogamma/(gamma+1)]
RE: flow through 3/4 nps sch 80 steel pipe
For a known flow rate and fL/D calcualte V
Pressure is obtained from energy equation
P=PoVo/V - (gamma-1)/2/gamma *G^2*V