Pipe-Flo viscosity density?

[eagle1900]

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!!!

 

[eagle1900]

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

 

[BigInch]

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/

 

[katmar]

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

 

[eagle1900]

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...

 

[eagle1900]

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

 

[BigInch]

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/

 

[eagle1900]

yes we can

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