Liquid Heat Capacity calculations using PC-SAFT

[tillkoen]

Hello everyone, I have a small problem. I measured experimental heat capacities for my components and want to use the data for parameter fitting. I then wanted to implement the fitting, when I noticed heat capacity calculations are not that straightforward.
I can calculated the resiual heat capacity, but not the total isobaric heat capacity and if I try, I get the Error: No ideal gas model initialized!

Now my question is, how can I initialize an ideal gas model? Or, how can I otherwise calculate the isobaric heat capacity with FEOS without the need for additional parameters or data?

I already did look in the documentation, but did not find anything on how to initialize an ideal gas model.
Looking forward to responsens. Thanks!

[g-bauer]

Hi and thanks for the question!

If I understand correctly you want to adjust parameters of a residual model (like PC-SAFT) to measured liquid heat capacities?
If that's the case, you have two options:

1. You extract the residual heat capacity from your experiments of the total heat capacity. To do so, you need an ideal gas model and subtract the ideal contribution from your measurements. There are several options depending on whether there exist parameters for your specific substances or not. With these residual heat capacities, you can use feos without any ideal gas models. So if you need an ideal gas model that is not implemented in feos, this is probably the way to do it.
2. You add an ideal gas model to feos. That's what you asked specifically. You can find an example in this notebook. When building the model, you simply add the ideal model to the residual model (in that order), e.g. feos.EquationOfState.pcsaft(pc_saft_parameters).dippr(dippr_parameters).

But you are right - we should properly document this with examples.