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Mass Flow Rate Calcs


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#1 Chem885

Chem885

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Posted 01 April 2015 - 06:47 AM

Hi,

 

I've recently started working for a company as a graduate engineer.

In one of the excel spreadsheets prepared by one of our senior engineers there is a section which calculates the mass flow rate in pipelines as below:

 

M=Ro * V * A

 

Where Ro= density of gas

V= Velocity 

A= Cross section area

 

We work on different projects with different pressures of natural gas but for all of them they use Ro=0.8 kg/m3 which is the density of natural gas in standard conditions and they don't consider the pressure of gas in the pipeline!

 

Please correct me if I'm wrong. I say they should calculate the gas density according to the gas conditions in the pipeline.

Your thoughts please.

 

Thank you.



#2 pdender

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Posted 01 April 2015 - 06:53 AM

yes, in that formula for mass flow I would include the density at "operating" conditions,

however I suggest to check the code to verify that it is mass flow with units Kg/s or equivalent,



#3 latexman

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Posted 01 April 2015 - 07:17 AM

Historically, gas/vapor volumetric flow at standard conditions has been used as a surrogate for mass flow rate.  What you have there is proof of this, but it's kind of the reverse, a surrogate mass flow rate.  There is nothing wrong with this as long as it is clearly stated the mass flow rate is based on a gas/vapor density at a specific T and P, i.e. standard conditions.  Most of the issues I've seen are because people get lazy and do not clearly state a T and P for a volumetric flow rate, or a surrogate mass flow rate in your case.


Edited by latexman, 01 April 2015 - 07:21 AM.


#4 Chem885

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Posted 01 April 2015 - 08:04 AM

Thanks guys.






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