Frection loss

[badr82]

Hi....
My questions is:
1-Is the three equations of calculating the head loss (Hazen-Williams formula, Darcy-Weisbach formula and Chezy-Manning formula) applicable all times in calculating the head loss?

2-If the pipe has many low and high points along the rout, how could I use these equations?

 

[MikeHalloran]

Read Crane Technical Paper 410.


Mike Halloran
Pembroke Pines, FL, USA

 

[bimr]

The Hazen-Williams equation is most frequently used in the design and analysis of pressure pipe systems. The equation was developed experimentally, and therefore should not be used for fluids other than water (and only within temperatures normally experienced in potable water systems). The Hazen-Williams formula is probably the most popular head loss equation for distribution systems.

The Darcy-Weisbach equation is a theoretically based equation commonly used in the analysis of pressure pipe systems. It applies equally well to any flow rate and any incompressible fluid.

The Chézy equation, in conjunction with Kutter’s equation, is widely used in sanitary sewer design and analysis. The Chezy-Manning formula is more commonly used for open channel flow.

The Hazen-Williams formula is often used for your application. You should assume a full pipe.

See the example in Chapter 8 of the linked document:

http://www.wbdg.org/ccb/ARMYCOE/COETM/tm_5_813_5.pdf

 

[PumpSmart]

badr82,

1. No.

2. It is water, yes. If different, you should use Darcy-Weisbach formula. If it is long pipeline you should analyse transient on hydraulics also.

 

[badr82]

It is water....
According to your replies, Hazen-Williams formula and Darcy-Weisbach equation are preferred.

 

[katmar]

If you have large differences between your high and low points you have much more important factors to consider than the method of calculating the friction head. Search for "Slack flow" and you will see there is a whole can of worms that you need to sort out before you worry about the niceties of accurate friction head calcs.

Katmar Software - Engineering & Risk Analysis Software

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[bimr]

badr82,

Did not recognize your handle at first.

Is this the same HDPE pipeline application that you posted a few weeks ago?

If so, your best option for calculations is to use the Hazen Williams. It is fully explained in the link above and the link includes sample calculations.

Transient flow,slack conditions, and other potential problems are also discussed in that link.

 

[PumpSmart]

badr82,
You will download a free basic TDH software calculator:

http://www.elefantin.nl/dP/download/dp_download.htm

Its apply for water and other viscous newtonian fluids.

I read your previous post, with a lot of data, do you find the problem? or could you resolve it?

If you see, this kind of basic equations and calculations , does not take care about low and high points along piping.
You have in mind three points: lowest, highest and final point.

In lowest point, make TDH calculation in this point.
In highest point, and make TDH calculation in this point.
and In final (discharge) point, and make TDH calculation in this point.

Then plot these 3 points in your pump curve and see what happen....if 3 points are in recommended range of operation.

Then analyse NPSH,

Then estimate time of transient, (time to fill piping)

Then, analyse slack flow....

Do you have pump curve?
Pump was lowara, SV8..., right?



I hope this helps.