Water properties Aspen Plus are off 1

[Luuk21]

Hi,

I have this annoying problem I'm unable to solve. When I add Water as a component in Aspen (CAS 7732-18-5) and run a Pure-property analysis, the Cp (specific heat capacity) is well off.

Where it should be around 4.2 from 0 to 100 degC, its going from 4.0 to 4.5.

I used different property methods; NRTL, NRTL-RK & WILSON but no luck.

I know I've fixed this in the past but I forgot how. How do I get the correct thermal properties of water back, and why is it off in the first place? Does this influence the binary pairs as well?

Thanks

 

[PaoloPemi]

probably it depends from selected thermodynamic package for enthalpy calc's...
for accurate results you should select ASME or IAPWS (95, the most accurate, or 97) these models however work only with pure fluids (not mixtures),
not sure about the models Aspen includes,
with Prode Properties I can select IAPWS 95 (the most accurate but supports only water) or (with mixtures) GERG 2008 or GIBBS_POLY (similar to REFPROP formulations), additional options (with reduced accuracy) LK / LKP or BWR,
perhaps Aspen has similar features, check on manual...

 

[Luuk21]

That did the trick, thanks - I used IDEAL and STEAM-TA for the water properties, apparently the steam tables use the wrong properties, which is very very confusing, changing to IAPWS-95 solved it.

Thanks!