torrensjoaquin/gerg2008

Code written by Eric Lemmon. Posted on the NIST website. But now in JavaScript, the best EOS for natural gases straight from the browser.

GERG2008

Code written by Eric Lemmon. Posted on the NIST website. But now in JavaScript, the best EOS for natural gases straight from the browser.

Github page in the following link...

https://torrensjoaquin.github.io/GERG2008/

The methane number according to EN16726 is also added as a result.

gerg2008's Issues

Doubt with residual parameters calculation

I have a doubt on how you calculate the residual Helmholtz energy, specifically the first derivative with the reduced density.

According to the GERG-2008 paper the polinomial term should be:

In your code, around line 555:

for(let k = 1; k <= kpol[i]; k++){
          ndt = x[i] * delp[doik[i][k]] * taup[i][k];
          ndtd = ndt * doik[i][k];
          ar[0][1] = ar[0][1] + ndtd;

For what I understood, taup[i][k] equals to n_{oi,k} * tau ^ t_{oi,k}. So each term of the derivative is calculated like:

delta^d_{oi,j} * n_{oi,k} * tau ^ t_{oi,k} * d_{oi,j}
When the term of the paper is:
delta^(d_{oi,j}-1) * n_{oi,k} * tau ^ t_{oi,k} * d_{oi,j}

I'm sure your code work, since I've tested a bit of it and reached good results, could you tell me what I'm reading wrongly?
(I'm trying to make my own implementation on Python and Fortran and not getting the expected results)

Thank you for your time!

Licence

Hi Joaquin,
There's no licence file in this repository, so I'm not sure whether you're open to this being used by others or if the code is just here for reference.
Would you mind adding a licence file? The convention is simply to put your licence terms in a file named LICENCE.md in the root of your repository. (I'd love to see it with an MIT licence, but anything describing permitted use would be helpful)
Thanks!