3 replies to this topic

[smalawi]

Hi,

did any one try to compare the results for vessel depressuring between hysys (unisim) and pro ii ?

In pro ii what is the recommended steps to size the depressuring valve or orifice ? any particlure areas to consider ?

cheer,

sm

[JoeWong]

My comments may discouraging nor disappointing some parties... i decided to keep...
Just simple advice...
Establish good basis for PV term and isentropic efficiency...
be careful flowrate and temperature predicted by HYSYS...
be careful temperature predicted by Pro-II...

Reader may choose to ignore my "observation"...

[smalawi]

My comments may discouraging nor disappointing some parties... i decided to keep...
Just simple advice...
Establish good basis for PV term and isentropic efficiency...
be careful flowrate and temperature predicted by HYSYS...
be careful temperature predicted by Pro-II...

Reader may choose to ignore my "observation"...

Hi,

I have checked my calcualtions with both Hysys (Unisim) and Pro II

Seems the results are very deferent and I cant tell which one is more accurate. I can compare the results with maual calcuations but still these are approximations !

Why would you say the flow and temperature in Hysys is questionable ?
Also why temperature in Pro II is questionable ? (Actually I see that it gives higher temperature than expected)

The PV term eff is about 100%, it could be lower but unless I have good reasons not to design at that temperature such as cost and delivery I will use it.

Aprecaite more comments and experiance based advise, for such a standared calcuation there seem to be more to learn !

cheers,

SM

[JoeWong]

I have checked my calcualtions with both Hysys (Unisim) and Pro II

Seems the results are very deferent and I cant tell which one is more accurate. I can compare the results with maual calcuations but still these are approximations !

What i really suggest to you is that browse through the HYSYS and Pro-II manual and looks for the equations used.

Secondly compare the detail results i.e heat transfer coefficient used, any mass inclusion, etc in order to identify the differences.

Did you use Groth equation for manual calculation or other method. Groth method only applicable to vapor only system.

Why would you say the flow and temperature in Hysys is questionable ?
Also why temperature in Pro II is questionable ? (Actually I see that it gives higher temperature than expected)

Results from Rigorous model and experiences...that's all i can say...

The PV term eff is about 100%, it could be lower but unless I have good reasons not to design at that temperature such as cost and delivery I will use it.

Read more in this... Hope it helps.
Isentropic Efficiency And Its Implications