pressure loss 1

[mjh250473]

The Darcy - weisbach formula is a linear pressure drop relationship, how can this be used to determine pressure drop in turbulent compressible flows. It is known that the rate of pressure drop is much greater as the gas travels downstream as compared the rate of drop when it is at relatively high pressure.

for this calculation and other related calcs what conditions should density, dynamic viscocity and ratio of specific heats be measured at.

What does the application of Colebrook - White friction factor actually mean in the Darcy equation.? I can see that it relates relative roughness to Reynolds number but nothing seems to be getting over my non linearity problem.?

 

[Latexman]

mjh,

The rules of thumb I remember are:

1. If pressure drop < 10% of P₁, you can reasonably use the Darcy-Weisbach equation using upstream or downstream conditions.

2. If pressure drop = 10 to 40 % of P₁, you can reasonably use the Darcy-Weisbach equation using the average of upstream and downstream conditions.

3. If pressure drop > 40 % of P₁, you should use compressible flow methods.

Each point along the pipe/channel will have a value of the Colebrook-White friction factor. If pressure drop > 40 % of P₁, there are compressible flow methods that handle this. Some use the average of the upstream and downstream Colebrook-White friction factor.

Good luck,
Latexman

 

[vzeos]

You may want to go to the attached site and check out paper 0112: - "A Tutorial on Pipe Flow Equations"

http://www.psig.org/Papers/archive.asp?year=2001&submit=Retrieve+Papers