Deviation in density calculation

[torlid]

Describe the bug
Significant deviation in density

To Reproduce
The density if gas phase in neqsim : 11.31
The density in Unisim: 11.15

1.4% deviation

The SRK model is used in both unisim and neqsim-python (v 3.0.11)

Should I expect "exact" same result in both Unisim and Neqsim, or is this what I should expect?

Steps to reproduce the behavior:

Gas composition:
component - value [mol%]
nitrogen - 1.09
CO2 - 1.67
methane - 83.48
ethane - 7.36
propane - 3.68
i-butane - 0.59
n-butane - 1.06
i-pentane - 0.28
n-pentane - 0.28
n-hexane - 0.16
water - 0.23
n-heptane - 0.1118
n-octane - 0.0182
T = 30°C
P = 13.813 bar a

Expected behavior
Equal values

[EvenSol]

Thanks for reporting this issue.

I tested the composition you reported with the SRK-EoS and reproduced your results using NeqSim. You can see my discussion in the following notebook:

https://github.com/EvenSol/NeqSim-Colab/blob/master/notebooks/thermodynamics/density_of_gas_using_SRK_EoS.ipynb

I suspect the density difference might be due to minor variations in the critical temperature (Tc), critical pressure (Pc), acentric factor or molecular weight of some components. If anyone could verify these results with other software, it would be helpful. My feeling is that the GERG-2008 EoS should provide the most accurate density calculation for this gas.

[torlid]

Thanks Even, for your reply.
Then I do not have to search for some error in my script :-)
Tore