oxygen @ 50 psi flow rate

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oxygendoc
Posts: 1
Joined: Wed Mar 03, 2010 12:06 am

oxygen @ 50 psi flow rate

Post by oxygendoc » Wed Mar 03, 2010 3:05 pm

I have a customer who asked me what flow in scfm is possible with 50 psi oxygen in a 100 foot long 3 inch ID pipeline. I tried using some of the calculators but I am not confident with my progress and was hoping someone with some expertise could assist. Thanks in advance.

tsprentall
Posts: 5
Joined: Tue Mar 02, 2010 1:12 pm

Re: oxygen @ 50 psi flow rate

Post by tsprentall » Wed Mar 03, 2010 6:17 pm

The maximum theoretical exit velocity can be calculated by writing the energy equation using a pressure differential (delta p) of 64.7 PSIA (assume constant source), zero frictional head losses in the pipe and zero elevation change. Manipulate the equation to solve for v2 and assume v1 = 0. The actual flow will be lower depending upon real head losses which can be estimated and real delta p which can be measured with pressure gages. Once you have the exit velocity, apply Q=VA to get volumetric flow. I've done this before and it works quite well, especially in order to recommend a measuring range for a meter.

V2=(129.4 lbf/in^2/rho)^1/2

admin
Site Admin
Posts: 361
Joined: Mon Feb 08, 2010 7:47 pm

Re: oxygen @ 50 psi flow rate

Post by admin » Wed Mar 03, 2010 10:27 pm

The theory of pipe flow basics will soon be available on web site, but until then...

Here is the part of it regarding your question (I presume that the oxygen is in gas state - not cryogenic):

For compressible flow of fluid from a pipe to a larger area or larger cross section like in the case of discharge to the atmosphere, a modified Darcy formula can be used:
w=1.111*(10e-6)*Y*d^2*(Δp*ρ1/K)^0.5
where is:
• w - mass flow rate [kg/s]
• Y - expansion factor [ - ]
• d - internal pipe diameter [mm]
• Δ p - pressure drop [Pa]
• ρ - density [kg/m3]
• K - resistance coefficient [ - ]
The expansion factor Y depends on the specific heat ratio, the diameter ratio β and the ratio of downstream and upstream absolute pressures.
For compressible flow through nozzles and orifice is:

Y=1-(0.41+0.35*β^4)*(Δ p/χ*p1)
where is:
• Y - expansion factor
• χ - specific heat ratio
• β - diameter ratio d1/d2
• Δ p - pressure drop
• p1 - inlet pressure
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tsprentall
Posts: 5
Joined: Tue Mar 02, 2010 1:12 pm

Re: oxygen @ 50 psi flow rate

Post by tsprentall » Thu Mar 04, 2010 1:56 pm

I have never come accross the compressible flow formula and mine actually used the wrong differential by 14.7 PSI (discharging from gage pressure to atmosphere...duh!)! Placing the correct value in my version yields about 283 SCFM. I'm going to work through the other using pipe k=0.04 and x=1.4. I'll let ya know what I come up with.

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