Inaccurate property methods about clapeyron.jl HOT 4 CLOSED

Hi Alex,

This is on us for not being clearer in the documentation. By setting up the models in this way, you've used the default ideal model which we call "BasicIdeal". This only carries a volume and composition dependence, no temperature dependence. This makes properties that depend on the first and second order temperature derivatives unusable.

Fixing this is relatively straight-forward, you can use the WalkerIdeal model since it has the parameters you need (we do need to greatly expand our database for the ideal models since these are quite lacking):

julia> using Clapeyron, Unitful

julia> N2_PR = PR(["nitrogen"];idealmodel=WalkerIdeal)
PR{WalkerIdeal} with 1 component:
 "nitrogen"
Contains parameters: a, b, acentricfactor, Tc, Pc, Mw

julia> N2_SAFT = PCSAFT(["nitrogen"];idealmodel=WalkerIdeal)
PCSAFT{WalkerIdeal} with 1 component:
 "nitrogen"
Contains parameters: Mw, segment, sigma, epsilon, epsilon_assoc, bondvol

julia> speed_of_sound(N2_PR, 101325u"Pa", 300u"K")
347.00051443031396 m s⁻¹

julia> speed_of_sound(N2_SAFT, 101325u"Pa", 300u"K")
347.0215687936945 m s⁻¹

julia> isobaric_heat_capacity(N2_PR, 101325u"Pa", 300u"K") / isochoric_heat_capacity(N2_PR, 101325u"Pa", 300u"K")
1.4016251686654189

julia> isobaric_heat_capacity(N2_SAFT, 101325u"Pa", 300u"K") / isochoric_heat_capacity(N2_SAFT, 101325u"Pa", 300u"K")
1.4014850964933816

The next area of focus for us is indeed the tests (and refining the docs); thank you for pointing this out!

from clapeyron.jl.

I've now added a very basic fix to the BasicIdeal model where it now includes the translational motions of the species; it's still not quantitatively accurate, but it will give more-reasonable values for these second derivative properties.

from clapeyron.jl.

Thanks, those values are now within 10-20% with BasicIdeal.

from clapeyron.jl.

Yes, it's not meant to be quantitatively accurate since nitrogen has rotational and vibrational modes not accounted for in the BasicIdeal model.

from clapeyron.jl.