How do I calculate %Liquid by Volume for a mixture

[AndrewLindsay]

Similar to the issue below, maybe I'm just too long since I've done any meaningful chemistry, but when I calculate the state of my mixture at a given temperature and pressure, is there a way to calculate the %Liquid by volume easily? It's been a long day trying to get my head back around Thermo, and any assistance would be appreciated.

[ianhbell]

Do you really want what you are asking for? Volume fractions are always tricky because volumes are not exactly additive in the way that mass and moles are.

But I could also imagine you have a cylinder of fixed volume and you just want to answer where the miniscus is. In that case you can get it from

vf_liq = V_liq/V_tot = (v_liq*n_liq)/(v_tot*n_tot) = v_liq/v_tot*x_liq

where:

v_tot = v_liq*x_liq + v_vap*(1-x_liq)

and x are mole fractions, and v are specific volumes (on a molar basis), and liq and vap correspond to the liquid and vapor, respectively.

[AndrewLindsay]

Yes, unfortunately that's what I'm after. I am trying to create up updated brittle fracture model using updated thermodynamics, and one of the key elements of the model is the volume fraction of liquids in the pipeline.

[ianhbell]

In that case, see my response above

[AndrewLindsay]

Thanks. That’s greatly appreciated.