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Line Sizing For Gas


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#1 manchester

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Posted 08 March 2010 - 12:55 AM

Hi there,

Darcy equation for pressure drop calculation is commonly use for incompressible fluid. And I always use Weymouth and Panhandle equation to calculate pressure drop is gas line.

However, I've seen some spreadsheet using Darcy or Hazen Williams equation for gas line sizing. It assumes that this equation only applicable for short pipe, where density is not vary significantly.

My question: Is it true to apply Darcy's equation to calculate pressure drop for gas line,for such assumption??

Thank you all...I'll appreciate your answers..

#2 fallah

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Posted 08 March 2010 - 01:47 AM

My question: Is it true to apply Darcy's equation to calculate pressure drop for gas line,for such assumption??


Yes,provided that Dp would be lower than 10% of inlet/upstream pressure.At this condition density wouldn't considerably changed and therefore gas could be considered as almost incompressible.

Edited by fallah, 08 March 2010 - 01:52 AM.


#3 manchester

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Posted 14 March 2010 - 10:53 PM

Yes,provided that Dp would be lower than 10% of inlet/upstream pressure.At this condition density wouldn't considerably changed and therefore gas could be considered as almost incompressible.
[/quote]

However, isn't it too conventional to use Darcy equation for gas,even though it considerably in low pressure drop? Because I found different number of DP if I calculate with Panhandle or Weymouth equation. Hence, I found that line size of gas can be lowered by 1 stage due to it fulfills pressure drop/100 m criteria, if I use Panhandle equation (still, i found that Weymouth and Darcy gives almost the same number of dp in short pipe).

#4 ankur2061

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Posted 15 March 2010 - 10:11 AM

manchester,

Try to get hold of Crane Technical Paper No. 410M. It is really a treatise on fluid flow. All the gas pressure drop equations are covered with the explanation for their usage.

BTW, Hazen-Williams equation is exclusively used for cold water flow. The most widely followed application for Hazen-Williams equation is for pressure drop & sizing calculations of fire water networks.

Hope this helps.

Regards,
Ankur.




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