1. Jun 21, 2006

TSN79

http://www.cda.org.uk/megab2/build/pub125/sec4.htm#5.1 [Broken]

...and I tried calculating head loss using both the forumla given, and the nomogram. Aren't these supposed to give the same result? Or am I missing something fundemental? Because they don't equal each other by a long shot...

An explanation would be very much appreciated :-)

Last edited by a moderator: May 2, 2017
2. Jun 21, 2006

Staff: Mentor

What data are you plugging in?

3. Jun 21, 2006

FredGarvin

The nomograms will be made from the equations for head loss. Unless a type-o was made in the webpage, they should coincide pretty closely. Are you sure you don't have a units snafu somewhere?

4. Jun 21, 2006

TSN79

I got them pretty much equal now, don't even know what must have gone wrong before. Damn units...

One more question for you guys:

I often see in literature that head loss is often set to 100 Pa/m pipe, at least for pipes bigger than 15 mm without further calculations, but almost all of my calculations show much higher values than this. Any idea why?

5. Jun 22, 2006

FredGarvin

To my knowledge, a number like that is a design parameter (rule of thumb) developed after a lot of experience. It is a target to shoot for, not an absolute. This would help calculate the pipe diameter.

I really can't imagine someone saying that "well, my pipe size is over 15mm. I guess my pressure loss will be 100 Pa/m no matter what I am doing." That just doesn't make much sense.

6. Jun 26, 2006

civil_dude

The average losses should depend on an assumed pipe TYPE. Each type should have a different average loss coefficient.

7. Jun 27, 2006

FredGarvin

Average loss coefficient? What is that? The only factor that would depend on the type of pipe is the friction factor. And then most people assume a smooth pipe on the first go around anyways.