Compressible Fluid Flow Calculation

[EVEN01]

Hi,

Recently I came across a copy of "Gas-Flow Calculations: Don't Choke from Trey Walters" that describes the behavior compressible fluids undergo as they travel down the line. He describes a series of steps and iterations to carry out in order to come up with an accurate solution to determining the mass flow rate of a gas in a pipe.
On the other hand I found a relationship for short lines(very simplified) in the latest edition of rules of thumb for chemical engineers.
Any leads on this? is there a "mid-point" between the very daunting task of having to divide the line and analyze each one of the divisions and the simplified version of the exercise?

Any help will be highly appreciated.

 

[BigInch]

Break the line up into segments such that no pressure drop in any segment is > 10% of the inlet pressure.

Get a flow program that will do gas pipelines.
Stoner Pipeline Simulator,
Pipeline Studio,
Olga2000,
Hire a consultant that knows one of the above.



**********************
"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/

 

[CJKruger]

EVEN01, if the pipe diameter is constant, you could use the isothermal compressible equation. It is iterative but not difficult. When you are done, just check the velocities to ensure they are all below sonic/sqrt(k).

As far as software is concerned. If you are worried about choke flow, then you have to specifically ask the software vendor if their software support choke flow. Most don't.

 

[EVEN01]

As a matter of fact the flow becomes chocked as the gas experiences both restriction and expansion.
I'd be more than happy to get a hold of some software to do the calculation however with the current economic downturn it is difficult to do since our corporate office cut our budget.
I think aft.com's compressible flow estimator should be able to carry out this calculation.

 

[CJKruger]

EVEN01, ask AFT before assuming it handles compressible choked flow correctly.

I am involved with Korf (

http://www.korf.co.uk)

and knows for a fact that it handles compressible choke flow correctly.

 

[4Pipes]

I would not have thought isothermal approximations should be used for sonic or near sonic. You should be using a Fanno line adiabatic calc. There are recommendations for the range of mach number for which isothermal should be used. (I cannot recall the exact range but it is definitely well below choking).