Liquid density calculation

[Usseglio]

Hi Jasper,

I am having inconsistency to calculate liquid density in COFE.
Density for liquid phase is calculated = zero.

All the compounds involved are new added from PCD.
Liquid density is set up by T- correlation (I double checked the equations ...).

In COFE, inside flowsheet configuration, property package definition, I am setting up the following:

For density liquid: Amagat
For density/volumen liquid: temperatura correlation.

Do you have any idea where I am doing wrong ?

Thanks,

Marcelo

[jasper]

Can you send me an example fsd file that shows this behaviour?

Thanks.

[Usseglio]

What I found is that if I remove Air from the compound list, liquid density is calculated correctly, if I add Air, then liquid density recalculate a wrong value of liquid density.

[jasper]

Can you send me an example?

[Usseglio]

Please find attached an example.

[jasper]

The calculation of liquid density for air results zero. Hence, the liquid volume is infinite. The entire phase volume becomes infinite, with the entire phase density thus zero again.

The Air correlation is evaluated extremely far outside of its validity range and evaluates to A/infinity.

I suggest you do not use the Air liquid density temperature correlation for this case.

In Configure|Property Calculations, change the pure compound liquid densities to "Compound defined"; then in Configure|Compounds, leave the liquid density for all compounds to T-correlation, except Air, change it to for example Rackett.

That should solve the problem.

I do not see a more generic way to "ease the pain" of extrapolation of arbitrarily shaped compound temperature correlations that far out of their range of validity.

[Usseglio]

Thank you Jasper.
It is a good way to overcome the issue.

[Usseglio]

Jasper,

I think that from last revisión of COFE the following action (I copied from a former reply ) is no longer available:

" ...In Configure|Property Calculations, change the pure compound liquid densities to "Compound defined"; then in Configure|Compounds, leave the liquid density for all compounds to T-correlation, except Air, change it to for example Rackett ... "

Thanks,

Marcelo

[jasper]

Which part?

1) If you go into the TEA property configuration, you can manually add the property "density / volume (pure)", or this will automatically be added in case a mixture density routine is configured that requires it, such a Amagat.
2) Then, one of the "density / volume (pure)" options for the liquid phase is "Compound defined".
3) Once that is selected, the Compounds tab will have a column "Liquid density". A drop down is available for each compound, which defaults to "T correlation" if available. If you click on the drop down, several options are available, including Rackett and Hankinson/Thompson (aka COSTALD).

At which part are you getting stuck?

[Usseglio]

My apologies ..., my mistake.
I was setting up in density pure Rackett method instead of compound defined, then density property was not appearing.

Sorry ...!!

The only thing is that when I executed CUP to get last revisión, it did not remain the same property package configuration for TEA that, I set up prior to update COFE.

Anyway, thanks for your always promp reply !!