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# Gas flow formula - multiple diameters of pipe in series

## Gas flow formula - multiple diameters of pipe in series

(OP)
Hello,

I am currently making a calculations spreadsheet for pipeline services and am thinking of how best to calculate gas flowrates. Liquid is simply the Darcy-Weisbach equation with Churchill (Darcy) Friction Factors.

However when it comes to gas, for example the dewatering of a liquid-use pipeline precommissioning, I am considering using the general gas flow formula described in "A Tutorial on Pipe Flow Equations" - Schroeder.

Currently I have five pipeline sections programmable, and a downline (hose) each could be different lengths and diameters.

Is there some form of this equation which accounts for the different sections?

If not, then I am considering setting an equivalent diameter of say 10" for example, and calculating the required length of this 10" pipe to generate the same back pressure as the original diameter and length of pipe, with the same flow rate. With all sections translated into the equivalent length of 10" pipe, then using this to calculate the required parameter. Is this acceptable?

Pipeline Services Engineer in the Oil & Gas Sector

### RE: Gas flow formula - multiple diameters of pipe in series

Friction factor is a function of both Reynolds Number (which includes pipe diameter as a first order parameter) and pipe diameter over pipe roughness. Don't try to make an homogenized "average" pipe diameter. Just run your sections as independent inputs to the next step. If you have a need of precision, your 10" answer will not satisfy it. If you are looking for order-of-magnitude numbers just use a simple chart that has upstream pressure vs. dP/unit length for various pipe sizes.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

### RE: Gas flow formula - multiple diameters of pipe in series

(OP)
Look's like I'll have to stop being and lazy and finding a work around and get coding then. Thanks alot.

Pipeline Services Engineer in the Oil & Gas Sector

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