Getting started

Fortran

Maybe you’ve heard of Fortran as that old and cryptic language that everyone is afraid of. Well, not anymore! Fortran is really easy to understand and has been updated a lot in the recent decades. There is a fairly direct guide on the fortran-lang site

Getting yaeos

yaeosis a Fortran library intended to be used as a fpm package, fpm can be easily easily obtained with the Python package manager pip with a simple:

pip install --user fpm

With fpm installed you can create a new Fortran project by running:

fpm new your_project_name

A new directory with the name of your project will be created.

You include yaeos in your fpm project by adding it as a dependency on your fpm.toml file by adding this:

[dependencies]
stdlib="*"
yaeos = {git="https://github.com/ipqa-research/yaeos"}

Or maybe you want a specific version:

[dependencies]
stdlib="*"
yaeos = {git="https://github.com/ipqa-research/yaeos", tag="0.1.0b2"}

Setting up a model

On yaeos there is a series of models implemented, right now we include Residual Helmholtz energy models (like Cubic Equations of State), but plan on extening to a broader variety.

In this example we’ll show how a model in yaeos can be used. We’ll take the Peng-Robinson equation of state as an example, but all the implemented models can be seen at yaeos__models. Inside your app/main.f90 file use

program main
    use yaeos

    ! Set the variable `model` as a generic `ArModel`
    class(ArModel), allocatable :: model

    ! Set the the variables that we're going to use
    ! as variable lenght arrays
    real(pr), allocatable :: n(:), tc(:), pc(:), w(:)

    n = [0.3, 0.7]    ! Number of moles of each component
    tc = [190, 310]   ! Critical temperatures
    pc = [14, 30]     ! Critical pressures
    w = [0.001, 0.03] ! Acentric factors

    ! Now we set our model as the PengRobinson76
    ! Equation of state.
    model = PengRobinson76(tc, pc, w)

end program

And then it’s all set, now we’ve set the model variable to use in our calculations

Calculating thermodynamic properties

Some thermodynamic properties can be calculated with yaeos models, and we’re adding more! In this example we’ll calculate a PV isotherm from our previously defined model. For the sake of simplicity all the next code blocks are assumed to be extensions of the previous one, before the end program sentence.

pv_isotherm: block
    real(pr) :: v, t, p   ! Thermodynamic variables
    real(pr) :: v0, vf, dv ! End and start volumes
    integer :: i, n_points ! iteration variable and how many points to calc

    v0 = 0.001
    vf = 10
    dv = (vf - v0)/n_points

    do i=1,n_points
        v = v0 + i*dv  ! Set new volume point

        call pressure(model, n, v, t, p) ! Calculate pressure

        print *, v, p
    end do
end block pv_isotherm

Also some useful derivatives are available when calculating each property, they can be easily accessed as optional arguments of the routine. For example, to obtain the derivative of pressure with respect to volume the line that calculates pressure should be changed to:

call pressure(model, n, v, t, p, dpdv=dpdv) ! Calculate pressure and dPdV

The available thermodynamic properties to calculate can be seen at the yaeos__thermoprops module.

Phase equilibria