Head Loss Calculation: Discrepancies?

In summary, the conversation on the given webpage discusses the calculation of head loss using both a formula and a nomogram. The participants initially noticed a discrepancy between the two methods, but later realized it was due to incorrect units. They also discuss the use of a standard head loss of 100 Pa/m in literature, which is a design parameter and not an absolute value. The average loss coefficient may vary depending on the type of pipe used.
  • #1
TSN79
424
0
I was reading on this page...

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

...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:
Engineering news on Phys.org
  • #2
What data are you plugging in?
 
  • #3
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
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
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
The average losses should depend on an assumed pipe TYPE. Each type should have a different average loss coefficient.
 
  • #7
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.
 

1. What is head loss and why is it important?

Head loss is the reduction in pressure that occurs as a fluid flows through a pipe or channel. It is important because it affects the performance and efficiency of various systems, such as water distribution networks and pumps.

2. What are some common discrepancies in head loss calculations?

Some common discrepancies in head loss calculations include using incorrect equations or assumptions, neglecting minor losses, and not accounting for changes in fluid properties or flow conditions.

3. How can discrepancies in head loss calculations be minimized?

To minimize discrepancies in head loss calculations, it is important to use accurate equations and assumptions, account for all sources of head loss (including minor losses), and use appropriate values for fluid properties and flow conditions. It is also helpful to validate the results with experimental data.

4. Can software or computer programs accurately calculate head loss?

Yes, there are many software and computer programs available that can accurately calculate head loss. However, it is important to verify the results and make sure all necessary inputs and assumptions are correctly entered.

5. How does temperature affect head loss calculations?

Temperature can affect head loss calculations because it can change the viscosity and density of the fluid, which in turn affects the friction factor used in head loss equations. It is important to account for these changes in temperature when calculating head loss.

Similar threads

Calculating Head Losses through a Pipe Network
    • General Engineering
Replies
11
Views
15K
I Is there a way to calculate expected value from probabilistic data?
    • General Math
3
Replies
76
Views
4K
Calculate head loss per meter clarification
    • Engineering and Comp Sci Homework Help
Replies
1
Views
1K
How Do You Calculate Head Loss in a Venturi Meter Using Bernoulli's Equation?
    • Introductory Physics Homework Help
Replies
3
Views
6K
Micro hydro turbine calculations
    • General Engineering
Replies
1
Views
2K
Concept subsea PHES system, /advice with calculations
    • Mechanical Engineering
Replies
8
Views
783
Calculating flow rate through turbine
    • Mechanical Engineering
Replies
6
Views
8K
How can the velocity at points of change in pipe systems be determined?
    • Classical Physics
Replies
4
Views
2K
Calculating mass flow rate while assuming shock losses
    • Engineering and Comp Sci Homework Help
Replies
1
Views
1K
I Linearity of power spectral density calculations
    • Calculus
Replies
3
Views
1K

Hot Threads

Recent Insights

Back
Top