flow direction
flow direction
(OP)
Hopefully this will be an easy question for most of you.
80Psi(alpha)
_____\_
/ |__/_____20Psi(beta)
| \
\|/
|
ATM(charlie)
If I connect a 1/4" pipe @ 20psi (alpha) to an 8" pipe @ 80psi (beta) will both fluids exit at "charlie"? Or will there be backflow into the "beta" stream. Please help. thanx
80Psi(alpha)
_____\_
/ |__/_____20Psi(beta)
| \
\|/
|
ATM(charlie)
If I connect a 1/4" pipe @ 20psi (alpha) to an 8" pipe @ 80psi (beta) will both fluids exit at "charlie"? Or will there be backflow into the "beta" stream. Please help. thanx





RE: flow direction
Patricia Lougheed
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RE: flow direction
Engineering is the practice of the art of science - Steve
RE: flow direction
RE: flow direction
Patricia Lougheed
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RE: flow direction
Thanks.
RE: flow direction
Just to make sure I understand you right, there is a 1/4" pipe (alpha) at 80 psi dumping into an 8" verticle header (charlie). 2 feet below that is another pipe (beta, unknown diameter) at 20 psi, also dumping into this 8" verticle header. 1 foot below beta is the 8" pipe opening to atmosphere.
Because of the relatively large size (8") of your header, I'd bet there is a good chance that both pipes, alpha and beta, will both discharge perfectly well, and there will be no backflow into beta. Unfortunately, the problem isn't sufficiently defined. The pipe ID's are unknown, and the fluid is unknown. Answer those and you can calculate losses more accurately, though I doubt the single restriction (1/4" pipe rapid expansion for alpha) is sufficient to properly define the flow from either pipe.
If you could better define the piping systems, say if there is a valve on alpha or beta near the header for example, and what that valve Cv and upstream pressure is, that would help tremendously in more accurately calculating the flow rates and thus the pressure drops inside the header.
RE: flow direction
An 8" line is coming from a pump at ground level and going up and into a tank which is 20' in heigh. The pressure in this pipe is 80psig. This is transporting water. I would like to inject NaOCL into the 8" pipe just before it dumps into the tank using a 1/4" line having a pressure of 20psig.
RE: flow direction
Couple questions:
Do you know the pump flow rate?
Is the 20 foot high tank at atmospheric pressure at the top (20 ft up)?
Where is the 80 psi measured (ie: how far from the tank/how long is the pipe before entering the tank)?
Are there any valves or other restrictions such as bends in the 8" pipe between where you're measuring pressure and the entrance to the tank?
RE: flow direction
RE: flow direction
I'm also assuming the control valve is in the 8" pipe between the pump outlet and before the 1/4" pipe. Do you know the Cv of that valve? Should I also assume the point at which you're measuring the 80 psi is before the valve?
Do you know the pump flow rate?
RE: flow direction
You need to determine the pressure in the 8" line where you are injecting at 20 psi via the 1/47" line.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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RE: flow direction
Naresuan University
Phitsanulok
Thailand
RE: flow direction
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com
RE: flow direction
That would be right if the pump is only dedicated to this service. Is it ?
RE: flow direction
You can therefore add in the 20 psi line. It is however standard practice to include a check valve to prevent backflow in the line.
If you add the small line just downstream of the valve you'll also get good mixing.
RE: flow direction
RE: flow direction
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: flow direction
Your 1/4" (6 mm) 80 psi nozzle flow has to expand into an 8" (200 mm) volume, so your Pressue Volume values have to change. You will probably get critical flow at the nozzle, a shock wave front, cooling and condensation, if not freezing in a two-phase fluid.
This is different to single phase liquid flow.
Johnp.Rz
http://www.mets.net.au
RE: flow direction
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: flow direction
My approach:
Calculate the total pressure(pressure head, velocity head and elevation) at the point where the fluid is to be injected. This calculation should be based on conditions as if there were no tap for injected flow.
If the calculated total pressure is less that the total pressure of the 20 psi source, there will be flow from the 20 psi source into the line. If the total pressure is greater than the 20 psi (total pressue) than some flow will go to the 20 psi as a reverse flow.
Regards
RE: flow direction