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# Pipe Segment And Gas Pipe In Hysys

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### #1 bentu

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Posted 07 October 2009 - 11:35 PM

Dear all,

i'm a beginner in HYSYS simulation, and my background is mechanical eng.
i just trying to make simulation for gas distribution piping.
i'm confuse what should i use to calculate pressure drop in piping,is it pipe segment or gas pipe.

for information, stream in single phase, gas only.
i try both of them and the result is difference.

### #2 daryon

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Posted 08 October 2009 - 12:35 AM

Dear Bentu,
Firstly I would recommend that you get hold of a copy of Crane Technical Paper 410M "Flow of Fluids" and have a read about the principles of compressible flow in pipes. This will give you a good background knowledge of gas flow in pipes and how pressure drop is calculated.

To answer your question you should be using the pipe segment in HYSYS to model your gas pipeline. The Pipe Segment is used to simulate a wide variety of piping situations ranging from single or multiphase plant piping and it also performs heat transfer estimation. You can enter the length of pipe and all the fittings. The fittings library within the pipe segment contains resistant coefficient data from Crane TP 410M and Perrys chemical engineering handbook and I believe is considered farily accurate. You can select a variety of 2-phase flow calculation methods, but for your single gas phase application the pipe segment will default to a modified version of the Darcy equation (see Crane TP 410M). The total heat loss from the pipe is also calculated using estimated heat transfer coefficients or user specified values on the Heat Transfer page of the Rating tab.

Edited by daryon, 08 October 2009 - 03:33 AM.

### #3 bentu

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Posted 08 October 2009 - 01:39 AM

Thankyou very much drayon,

and then when we use gas pipe? in what condition?

### #4 daryon

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Posted 08 October 2009 - 03:50 AM

Thankyou very much drayon,

and then when we use gas pipe? in what condition?

Hi again bentu,

Sorry mate i have deleted a bit of the previous post about velocity as it is not really relevant. Please let me clarify....

I don't ever use the gas pipe. To quote Aspentech "The Compressible Gas Pipe unit operation is primarily designed for transient calculations with streams. Steady state calculations have been implemented primarily for initialization of the Pipe State prior to transient calculations." Basically it is for use with the HYSYS dynamics liscense the only reason it is avaialble in the steady state mode is to set-up the pipe proir to switching to dynamic mode. If you have a dynmaic liscense (these are expensive) you may consider using it to moodel a pipeline and calculate the affects of process transient (changes in flow and pressure).

The pipe segment is more than adequate for you pipeline. It will break you pipe up into small increaments and calculate pressure loss using the Darcy equation for each one. The limitation of the Darcy equation is that it assume a constant density, according to Crane if the pressure drop along the pipe is greater than about 40% of the inlet pressure that the Darcy equations accuracy is unacceptable. The HYSYS pipe segment gets round this by splitting the pipe into small incremants and solving for each one, the result of the previous calculation increment is used as the input to the next. If the there is a pressure drop of greater than 10% across a increment then HYSYS will flag up an warning message and you will need to increase the number of increaments that pipe is split into. The default is 5 increments per pipe segment.

Hope this helps

### #5 bentu

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Posted 08 October 2009 - 08:43 PM

Regards,
Bentu

### #6 2solver

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Posted 09 October 2009 - 02:44 PM

Did you try SysEC from www.hyprentech.com? This software is for single phase and two phase line sizing.