2 replies to this topic

[Dmitry]

Hello all,

In Hysys I found next:

Water, at + 4 C, 1.013 bar:

Mass density is 1023 kg/m3
Std. Ideal Liq. mass density is 998 kg/m3
Liq. Mass density (Std. Cond.) is 1015 kg/m3


Why is the mass density in Hysys of water does not correspond with mass density from open resource, such Engineering ToolBox and another?
What is the difference between these 3 parameters? I tried to contact Aspen Support but I didn't understood their answer, probably someone will explain me "very simple"

Regards

[PaoloPemi]

while I consider a 2% error acceptable for many calc's possibly you may get more accurate values setting a specific model as the steam tables,
for your reference I give the values for water density at 4C calculated with Prode Properties

IAPWS 95 -> 999.9749 Kg/m3

Regular->1003.947 Kg/m3

Peng Robinson Extended -> 1018.397 Kg/m3

in this case the errors are about 0.3% with regular model and 1.8% with the Peng Robinson equation of state,
of course Peng Robinson gives much more flexibility with mixtures (say water + hydrocarbons)
As alternative to extended EOS you may try Costald or equivalent procedures

[Technical Bard]

Mass Density is actual at stream conditions
Std Ideal is ideal solution at 15°C / 1 atm (or 60°F and 1 atm - it will change with the temperature units).
Std Mass Density is the actual value at 15°C and 1 atm (or 60°F and 1 atm).

The reason HYSYS disagrees is that it depends on the property package you choose. ASME Steam (1967) versus NBS Steam (1984) or other may differ from other packages.