flow equation for biogas line
flow equation for biogas line
(OP)
Hallo,
I am trying to choose proper equation to calculate pressure drops in biogas grid (50km) (CH4-0.6, CO2-0.4), pressure range is from 1 to max.20 bars, material is PE100. I thought about Spitzglass (>1psi).
Anybody can help?
I am trying to choose proper equation to calculate pressure drops in biogas grid (50km) (CH4-0.6, CO2-0.4), pressure range is from 1 to max.20 bars, material is PE100. I thought about Spitzglass (>1psi).
Anybody can help?





RE: flow equation for biogas line
Independent events are seldomly independent.
RE: flow equation for biogas line
RE: flow equation for biogas line
Independent events are seldomly independent.
RE: flow equation for biogas line
With a 50 km line you probably want a gas flow equation. Just a thought. You could use
- Panhandle A if your Reynolds number is between 5E6 and 1E7
- Weymouth if your pressure never exceeds 9 barg and you can ignore the assumption that the gas has zero CO2 or H2S
- AGA Fully Turbulent if you want to run concrete pipe (all of the modern pipes have an effective roughness outside the fully-turbulent region of the Moody Diagram)
- You could use the Isothermal Gas Flow equation if you never go below 6000 Reynolds Number and you have no condensation, and downstream density never drops below 90% of upstream density, and you don't have any heat transfer to or from the environment, and no work is done on or by the fluid
The only one that has any chance of matching measured pressure drops is Isothermal Gas Flow, but you may have to break up the line into fairly short segments to satisfy the incompressible assumption.I find that if I ignore compressibility I get farther and farther and farther from the calculation matching reality. Let's say that over your 50 km you drop from 20 barg to 1 barg at 30 C (which means that you had to break the line up into something like 1 km segments and solve it 50 times), the value of the compressibility of your gas increases about 4%. So to get +/-10% everything else has to be within 6%. Not a handicap I am going to give up easily. When I do this kind of problem I recalculate average pressure, friction factor, and compressibility for each step.
David Simpson, PE
MuleShoe Engineering
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RE: flow equation for biogas line
Thank you for all help!
RE: flow equation for biogas line
First off are you sure you don't have or wont have any liquids in this system as that will screw up any calcuations you have as they are all based on single phase gas.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: flow equation for biogas line
RE: flow equation for biogas line
Compressibility can be ignored with little loss of accuracy, when pressures are less than 200 psig.
Do NOT use Weymouth! That's for 20" + diameter, high pressure and long length.
Independent events are seldomly independent.
RE: flow equation for biogas line
Thank you BigInch.
RE: flow equation for biogas line
PE pipe pressure rating already allows a large element for aging and long term effects so don't double dip and end up with thicker pipe than you need.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: flow equation for biogas line
Thank you once more.