gas flow

[VikingUK]

I have gas flowing through a pipe and have calculated the velocity. I now need to decrease the velocity for a pigging operation. I can calculate the flow I need at the new velocity but need to work out the pressure at these conditions. Does anyone have a link to an online calculator or any othe radvice on the calculation I should use.

 

[BigInch]

You can get any pressure. It depends what you hold at the inlet, or what you hold at the outlet and the flowrate. Pressure drop between the inlet and outlet will be the sum of friction loss at that velocity + what's required to move the pig along.

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"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/

 

[VikingUK]

thanks.... no wonder I could not calculate it the way I tried ! I can just use a pressure drop calculation then given that I know flow and velocity ?

 

[BigInch]

Exactly right. You can't calculate 3 unknowns with 1 equation. You have to set 2 of the three variables, inlet pressure, outlet pressure, or pressure drop and calculate the remaining unknown.

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