×
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

Simple Formula for pressure in pipe

Simple Formula for pressure in pipe

Simple Formula for pressure in pipe

(OP)
I am looking for a simple formula to compute pressure drop in a straight new pipe(basically no friction). Its just a simple 2' straight pipe with water flowing in it. How do you figure pressure drop? Is there a simple formula for pressure drop in a pipe?


Thank you for your time.  

RE: Simple Formula for pressure in pipe

Check Moody chart or equivalent equations in a fluids book or engineering handbook.

Unless the pipe is awfully small or the flow rate is awfully high, the pressure drop in 2' will be negligible.

RE: Simple Formula for pressure in pipe

use Hazen Williams Hydraulic Tables / formula
V = 1.318C * r^.63 * s^.54

V = avg velocity
C = discharge coefficient
r = hydraulic radius
s = h/l = energy loss per foot of pipe

values for C can be found in many textbooks and vary depending upon size, type and condition of pipe

you may also want to try the Handbook of Hydraulics by Brater and King

RE: Simple Formula for pressure in pipe

Before you get too caught up in the equations, there are plenty of tabulated books for easy reference.  Just tell us the pipe material (steel, copper, plastic, etc.), the size of the pipe (nominal diameter or actual), and the flow rate (gpm) or velocity of the water.

RE: Simple Formula for pressure in pipe

(OP)
Thank you for all the input ... the pipe is copper the id is .5 its actually two 24" lengths joined by two 90s and a 4" section of pipe to make a long U the flow is 2.5 gpm.


Once again thank you for all the help.

RE: Simple Formula for pressure in pipe

eegeek,

I think you'll have not much -- something between 0.5 PSI and 1 PSI drop.  If you desire accuracy, plug your data into the calculator on this link:
 http://www.efunda.com/formulae/fluids/calc_pipe_friction.cfm#calc

If you consider your two elbows to be equal to about 4 feet each of equivalent straight pipe length, you'll be pretty close.

Enjoy!

Old Dave

RE: Simple Formula for pressure in pipe

I agree with Old Dave's approximation.  I get about 0.7 psi or 1.6 ft H20 drop.  I was assuming about 3.1 ft of equivalent length for each elbow which brings your total "hydraulic" lenght up to ~8.53'.

RE: Simple Formula for pressure in pipe

eegeek: this is the pressure drop for headloss due to the flow velocity.  you may also need to add (or subtract) due to the change in elevation from one end of the pipe to the other.

RE: Simple Formula for pressure in pipe

Oops.  Forgot to add in the last 2'.  I should have said:
0.86 psi or ~2 ft H2O drop (based on an hydraulic length of 10.53' and a pressure drop of 18.8'/100').

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