Determining Flow from a forcemain

[Zorq]

Hi all,

I have been tasked with determining the friction loss and flow in a system. I have the pipe sizes and lengths, pumps, and pump run time hours.

My question is can I use the Velocity formula derived from the Hazen-Willams formula, and plug that velocity into the Darcy equation for the Headloss due to friction in the system?

My goal is to find the total head loss in the system and plot it on the pump curve for to obtain the flow.

 

[jgailla]

If you're doing a forcemain it doesn't have to be that complicated.
Find your equivalent system length. Determine several flow rates which will be well above, below, and through your expected flow.
Use Hazen-Williams with an appropriate C value (usually 120 for PVC) for each flow rate and that will generate your curve with velocity on the x-axis and headloss on the y-axis. You have a range of flows. I usually use about 6-8 points and that will get you a good curve.
Draw the system curve (which is independent of the pump curve) directly on the pump curve and the intersection is where your pump will operate.
The headloss in the system will be dependent on the flow rate.

 

[bimr]

The calculation is most easily accomplished using the equivalent length method. Here is a link to an example:

http://www.engineeringtoolbox.com/equivalent-pipe-length-method-d_804.html

 

[rconner]

Is this an existing, or instead in some fashion conceptual system?