3 replies to this topic

[Frya_R]

Hello,

 

So I'm having this problem in designing a simple pipe segment, in hysys,

its a pipe segment of,

 

od 24" and id of 22.8699" that is 25 miles long with inlet conditions of 60barg, 86F, and 652MMSCFD, with friction factor of 50 microns, and I cant manage to get it it right.

 

I'm a relatively new process engineer, I know I can increase the diameter or increase inlet pressure and all that, but my supervisor says its a problem with the heat transfer.

 

can you guys help me figure this out I've been at it for two days I feel like I'm missing something very simple.

 

the following is the attached hysys file.

 

thanks for your time.

[katmar]

I was unable to see your data file, so I have assumed the gas to be pure methane to determine the physical properties. This will give a ballpark estimate and an indication of the problem.

The attached image shows the pressure drop and exit velocity calculated in AioFlo using the isothemal compressible model. If there are heat losses along the pipe the density of the gas will be slightly higher and the pressure drop lower by a couple of percent, but the overall picture will not change significantly. At these high pressure drops and Reynolds Numbers the calculated pressure drop is very sensitive to the pipe roughness and the margin of error is higher then usual.

The reason for Hysys to not solve the problem may be that the gas properties are significantly different from pure methane, or they may have put checks into the solution algorithm that do not allow such a high pressure drop relative to the inlet pressure.
 

Attached Files

•  Frya_R Cheresources 20 July 2025.gif   101.01KB   0 downloads

[Frya_R]

I was unable to see your data file, so I have assumed the gas to be pure methane to determine the physical properties. This will give a ballpark estimate and an indication of the problem.

The attached image shows the pressure drop and exit velocity calculated in AioFlo using the isothemal compressible model. If there are heat losses along the pipe the density of the gas will be slightly higher and the pressure drop lower by a couple of percent, but the overall picture will not change significantly. At these high pressure drops and Reynolds Numbers the calculated pressure drop is very sensitive to the pipe roughness and the margin of error is higher then usual.

The reason for Hysys to not solve the problem may be that the gas properties are significantly different from pure methane, or they may have put checks into the solution algorithm that do not allow such a high pressure drop relative to the inlet pressure.
 

if i may ask why would it be a problem if the gas properties differ from pure methane? i mean it is not purely just methane but the composition is taken from a real natural gas that is more than 90% mthane

[katmar]

The relevant properties are the viscosity and the molecular weight.

 

Changes in viscosity will have a very minor effect.  The viscosity affects the Reynolds number which in turn affects the friction factor.  But at high Reynolds Numbers the friction factor is almost independent of the Reynolds Number - and therefore independent of the viscosity.

 

The molecular weight affects the density and the mass flow rate (for a constant flow expressed at standard volumetric conditions).  So if the MW is higher than that of methane the density will be higher than that of methane and the mass flow rate will be higher than the 320 lb/s we had previously.  This will result in a higher pressure drop than I showed in my previous post.  Conversely, if the MW is lower than that of methane the pressure drop will be lower.

 

What viscosity and molecular weight did you enter into Hysys?