Pressure drop due to pump

SnekaySquid · July 2, 2024, 20:37

Hi,

I need to calculate the pressure drop across a vertical pipe with a pump, the problem is I have no clue how to add the pump. The pump has a flowrate and a pressure given( 3PGM and 55psi). I don't know how to include it such that the pressure drop reflects it. I know there is a way to use a momentum source to model a pump, but I don't know how this will affect my pipe.

All help would be useful. the geometry is very simple (a cylinder as a pipe).

xisluke · July 4, 2024, 05:05

Quote:

Originally Posted by SnekaySquid

Hi,

I need to calculate the pressure drop across a vertical pipe with a pump, the problem is I have no clue how to add the pump. The pump has a flowrate and a pressure given( 3PGM and 55psi). I don't know how to include it such that the pressure drop reflects it. I know there is a way to use a momentum source to model a pump, but I don't know how this will affect my pipe.

All help would be useful. the geometry is very simple (a cylinder as a pipe).

Maybe I didn't get the question correctly but the pressure drop in a pipe does not depend on the pump, given an incompressible fluid the characteristic curve of your system (therefore the losses and the pressure drop) depends on the pipe itself. If there is a specific volumetric flow rate of fluid flowing into the pipe, the pressure drop will be somehow proportional to velocity^2; it is something that you can estimate with a Moody chart or some other semi-empiric correlation for internal flows in pipes. Obviously in your case the pipe is vertical and you need to account also for potential energy.

If you need to do a check with Fluent you can impose a fixed velocity at the inlet of the pipe and a fixed static pressure at the outlet, the code will evaluate the drop that the pump will need to overcome.

SnekaySquid · July 7, 2024, 15:07

According to my calculations, the pressure drop is calculated using the energy equation, where the driving pressure change is due to head loss from a pump. the potential and frictional parts play a role as well, but not as significant. My problem is I cannot find a way to show this in Fluent.

At the inlet: I put flowrate (as a velocity) at the pumps pressure (55psi or 380Kpa)
At the outlet: I keep that at 0 gage pressure

Yet for what ever reason the answer is never close to that and is around 1Pa
which is the frictional loss in the pipe.

July 2, 2024, 20:37	Pressure drop due to pump	#1
SnekaySquid New Member karl Join Date: Jul 2024 Posts: 3 Rep Power: 2	Hi, I need to calculate the pressure drop across a vertical pipe with a pump, the problem is I have no clue how to add the pump. The pump has a flowrate and a pressure given( 3PGM and 55psi). I don't know how to include it such that the pressure drop reflects it. I know there is a way to use a momentum source to model a pump, but I don't know how this will affect my pipe. All help would be useful. the geometry is very simple (a cylinder as a pipe).

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July 7, 2024, 15:07		#3
SnekaySquid New Member karl Join Date: Jul 2024 Posts: 3 Rep Power: 2	According to my calculations, the pressure drop is calculated using the energy equation, where the driving pressure change is due to head loss from a pump. the potential and frictional parts play a role as well, but not as significant. My problem is I cannot find a way to show this in Fluent. At the inlet: I put flowrate (as a velocity) at the pumps pressure (55psi or 380Kpa) At the outlet: I keep that at 0 gage pressure Yet for what ever reason the answer is never close to that and is around 1Pa which is the frictional loss in the pipe.