×
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

Pipe-Flo viscosity density?

Pipe-Flo viscosity density?

Pipe-Flo viscosity density?

(OP)
Someone know if PipeFlo consider the difference between viscosity or density...

I've done test and for 2 systems identical + one at 20 cps and the other at 200 cps... I find the same pressure and flow ...

Is PipeFlo not enable to see or simulate the difference?

Thanks!!!

RE: Pipe-Flo viscosity density?

(OP)
I mean is Pipe-flo able to see the difference of viscosity? or the difference of density?

RE: Pipe-Flo viscosity density?

I don't use it, but I'm totally sure it must.
I suspect your pipe isn't long enough, flowrate is small  and the pipe is flat (same inlet & outlet elevations).  What flowrate, diameter, length and what Reynolds number did you have in each case?

To see a pressure difference due to density alone enter a vertical pipe with no flow.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pipe-Flo viscosity density?

It is theoretically possible that the viscosity change makes no difference to the pressure drop and flow, but most unlikely in practice.

If you look at the Moody (or Fanning) friction chart you will see that in the upper right portion of the chart the lines are horizontal - i.e. the friction factor is independent of the Reynolds number.  The only influence that viscosity has in the Darcy-Weisbach formula is via the friction factor, and if you are in a regime where the friction factor is independent of the Reynolds number then the viscosity would not impact on the pressure drop.

However, to get into this part of the Moody chart you need to have a high Reynolds number and/or a high roughness to diameter ratio.  In practice a high roughness to diameter ratio means a small pipe.  The combination of a small pipe with a 200 cP viscosity means that it is almost impossible to reach the high Reynolds number required.

If you do have laminar flow (likely with high viscosities) then it is correct that the density has no impact on the pressure drop for a horizontal pipe with a fixed volumetric flow. In laminar flow the Darcy Weisbach formula collapses to Poiseuilles's law and the head is proportional to
  (viscosity x length x velocity) / (diameter^2 x density)

To convert from head (units of length) to pressure drop you must multiply by (density x gravity).  This cancels the density term and therefore, for a given volumetric flowrate and a constant velocity, the pressure drop (in pressure terms, not head) is independent of density.

This means that it is not possible to say whether your software is behaving correctly unless we have actual examples.
 

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Pipe-Flo viscosity density?

(OP)
Well hear an exemple :

pipe 1: 10 000Ft, diam. 8 inch, Steel, Roughness 0.0018inch, Schedule 40, elevation 0 to 0ft
With fluid : Water at 15.6C, pressure 0psig, density 999 and visocsity 1.121. Design limit: velocity 0 to 200ft/s, pressure -14psig to 1000psig


pipe 2: 10 000Ft, diam. 8 inch, Steel, Roughness 0.0018inch, Schedule 40, elevation 0 to 0ft
With fluid : XXX at 15.6C, pressure 0psig, density 1000 and visocsity 200. Design limit: velocity 0 to 200ft/s, pressure -14psig to 1000psig

And I don't see difference...

RE: Pipe-Flo viscosity density?

(OP)
My source is 20psig at 0 ft (like a tank)
the output is 100gpm

RE: Pipe-Flo viscosity density?

velocity 0 to 200 fps, 14 to 1000 psig, what are you doing?

Can you just pick one flowrate, keep inlet pressure the same and change viscosities?

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Pipe-Flo viscosity density?

(OP)
yes we can ;)

I only try to understand how react Pipe-flo! haha!

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