×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

HGL vs EGL

HGL vs EGL

HGL vs EGL

(OP)
I am trying to recalculate the HGL of a simple run of pipe after adding 3 more cfs into the system that it wasn't originally designed for. (Original design used wrong C factor in rational formula) I have a known elevation of the HGL and velocity at any given point along the stretch of pipe.

We know that the EGL = HGL + velocity head ((V)(V)/2g).

If I start at a point where the HGL is known, lets say it's 2-ft above the crown of the pipe. I also know the velocity at this point, say 5 ft/s. So in calculating the EGL = 2-ft + (5)(5)/2g = 2.38 ft.

Now if we introduce an additional 3 cfs into the pipe, the new velocity through the pipe increases, (v=q/a) which makes the velocity head also increase.

Subtracting the new velocity head from the calculated EGL, the new HGL is lower than the old HGL.

So there must be something wrong with my approach. Adding more fluid into the system couldn't lower the HGL, it would have to raise it.

What am I doing wrong here?

Maybe by adding the 3 cfs and increasing velocity, I also add to the frictional losses that determine the HGL in the first place. So while the velocity head grows, so does the frictional loss. Making the overall HGL rise?



RE: HGL vs EGL

yes

RE: HGL vs EGL

You must have realized it already.
Assuming additional 3 cfs flowing through the same pipe means you (unknowingly) changed both the HGL and EGL.
So you just start again from scratch. Re-calculate both HGL, velocity and EGL.
Thanks

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources