Pressure drop through nozzle
Pressure drop through nozzle
(OP)
If I have a system like this...
1" 0 psig
^
|
3" 80 GPM 60 psig>-----------|----------> ? psig, 3"
How do I find the pressure drop across the tee if the 1" line is dumping water to atmospheric pressure. Basically I need to find an equation that finds the pressure in the right hand pipe taking into account a loss of mass flow. I couldn't find one anywhere.
1" 0 psig
^
|
3" 80 GPM 60 psig>-----------|----------> ? psig, 3"
How do I find the pressure drop across the tee if the 1" line is dumping water to atmospheric pressure. Basically I need to find an equation that finds the pressure in the right hand pipe taking into account a loss of mass flow. I couldn't find one anywhere.
-Mike





RE: Pressure drop through nozzle
RE: Pressure drop through nozzle
-Mike
RE: Pressure drop through nozzle
1" pipe length
3" pipe length
and either, or both of these
1) the flowrate in the 1" and/or the 3"
If you only know one of those, then we need this one too,
2) the end pressure at the outlet of the 3"
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Pressure drop through nozzle
Say the flowrate in the 1" line is 40 GPM.
This is a conceptual question so we really don't have to take into account line losses but included them just in case. I just needed some direction on how to calculate the pressure drop.
-Mike
RE: Pressure drop through nozzle
flowrate in the outgoing 3",
flowrate in the outgoing 1",
or
pressure at the end of the outgoing 3".
Without those, flow in both pipes is 0 to 80 gpm.
If you just want to try a very rough estimate, assuming the end pressure at the 3" is also 15 psi and pipe roughness is zero, ratio by pipe area and the 3" would have 72 gpm with 8 gpm in the 1".
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Pressure drop through nozzle
I'm thinking that the minimum bypass line is too small to handle the extra 220 GPM, since the 1" pipe is 20 ft long and I get a huge pressure drop of about 310 psig at 220 GPM. It looks like the max flow I can get out of the 1" line is around 90 GPM, since the pressure drop is about 55 psig for this flow.
Am I looking at this the right way?
(I realize how bad the design is, the bypass is only a temporary fix).
-Mike
RE: Pressure drop through nozzle
Anyway... if you want to recirculate more flow than that now, you'll have to size that recirc line for the flowrate you want now using a differential pressure equal to the pump discharge pressure (45 psig) minus the 1" outlet pressure (of the tank at 15 psig) and the 20 ft of length. Which looks like you can have a dP of 30 psi drop to work with. Size the line, let's say that's a 1-1/2". Then find a 1" or 1-1/2" control valve that will do that flowrate with the same pressure drop and at about the 70% open position.
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Pressure drop through nozzle
Good luck,
Latexman
RE: Pressure drop through nozzle
Seems to me like 50% throttling continuously will lead to pump problems pretty quickly without a good bypass flow.
-Mike
RE: Pressure drop through nozzle
I've seen values as low as 10% and occasionally run into them as low as 2% -- that one didn't survive.
Patricia Lougheed
******
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RE: Pressure drop through nozzle
20% is usually a reasonable minimum, 10% might be an absolute minimum, but heating is likely, so only do that if the manufacturer agrees, and neither for extended operation times. If its a large pump, these rates should only be used for startup, or shutdown sequences.
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Pressure drop through nozzle
-Mike
RE: Pressure drop through nozzle
Good luck,
Latexman
RE: Pressure drop through nozzle
Good luck,
Latexman
RE: Pressure drop through nozzle
thanks again
-Mike
RE: Pressure drop through nozzle
Good luck,
Latexman
RE: Pressure drop through nozzle
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Pressure drop through nozzle
just kidding...info from goulds is
3796 MTX 3x3-13 - 12 1/8" impeller, 1770 RPM
Min hydraulic flow 58.8 GPM
so that would mean that for the 3/4" (went back out in the field and found it was 3/4" SCH 40 NPS and not 1") line with 20' of piping and a minimum flow of 58.8 GPM, I would need about 56 psid to overcome the friction losses.
-Mike
RE: Pressure drop through nozzle
Good luck,
Latexman
RE: Pressure drop through nozzle
-Mike
RE: Pressure drop through nozzle
Good luck,
Latexman