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!

*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.

Jobs

Hydraulic Analysis -fluid mech

What is the difference between Fanning and Moody friction factors? by chemebabak
Posted: 6 Oct 11


Many folks calculate 4 times greater head loss (or 4 times less) than the actual friction loss.  This comes from confusion between Moody and Fanning Friction factors.  Some friction factor graphs are for Moody Friction factor, which is 4 times Fanning friction factor.  That is, f = 64/Re is Moody and f = 16/Re is Fanning.

Be careful with your hydraulic calcs.  It is easy to mix the two and calculate 400% greater (or 25% less) head loss.  The calculation for head loss in feet is:

using Moody Friction factor -
h(friction) = f(M) * (L/D) * v^2 / (2 * g)

using Fanning Friction factor -
h(friction) = 4*f(F) * (L/D) * v^2 / (2 * g)

where,
h(friction) = head loss by friction in feet
f(M) = Moody Friction factor
f(F) = Fanning Friction factor
L = length in feet
D = pipe inside diameter in feet
v = velocity in ft/s
g = 32.174 ft/s^2, acceleration due to gravity

The Colebrook-White equation is an iterative method that calculates Fanning friction factor.
f(F)^2 = 1 / ( -4 * Log(eps / (3.7 * D) + 1.256 / (Re * √f(F) )

where,
eps = pipe roughness in feet
Re = Reynold's number


 

Back to Chemical plant design & operations FAQ Index
Back to Chemical plant design & operations Forum

My Archive


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close