Procedures

Soave $\alpha$ function and it’s derivatives.

MathiasCopeman alpha function definition

$A^r$ models consistency tests.

Wrapper subroutine to the SRK/PR Residula Helmholtz function to use the general interface

Define beta limits to avoid overshooting when solving the Rachford-Rice equation.

Modify K-factor values to assure that $\beta$ lies between (0,1)

Mixture repulsive parameter.

Quadratinc mixing rule for the repulsive parameter.

Quadratinc mixing rule for the repulsive parameter, using $b_{ij} = \frac{b_i + b_j}{2} (1 - l_{ij})$ as a combining rule.

Numerical continuation of a function.

Calculate residual heat capacity pressure constant given v and t.

Calculate residual heat capacity volume constant given v and t.

Constant $\delta_1$ parameter.

RKPR $\delta_1$ parameter mixing rule.

Calculate the mole fraction second derivatives respect to mole numbers

Calculate the mole fraction first derivatives respect to mole numbers

Attractive parameter mixing rule with quadratic mix.

Mixing rule at infinite pressure as defined in the book of Michelsen and Møllerup.

Convert the mole fraction derivatives of a quantity (calculated so they do not sum to 1) to mole number derivatives (where the mole fractions do sum to one). Requires the derivatives and the mole fractions of the mixture. From https://chemicals.readthedocs.io/chemicals.utils.html?highlight=dxs_to_dns#chemicals.utils.dxs_to_dns

Calculate residual enthalpy given volume and temperature.

Calculate residual entropy given volume and temperature.

Error function for phase-equilibria optimization. Using two-phase points and an error function of:

Calculate the excess Gibbs free energy and its derivatives of the UNIQUAC model.

Calculate the Gibbs excess energy of the UNIFAC model

Excess Gibbs model generic interface

Flash algorithm using sucessive substitutions.

Function that needs to be solved at each envelope point

Wrapper function to use the objective function with the Nelder-Mead algorithm

Calculate logarithm of fugacity, given pressure and temperature.

Calculate fugacity coefficent given volume and temperature.

Subroutine to solve a point.

Calculate the UNIFAC combinatorial term of Gibbs excess energy

$G^E$ models consistency tests

Evaluate the UNIFAC residual therm

Residual Helmholtz Energy for a generic Cubic Equation of State.

Get index of the maingoup with id: maingoup_id

Get the interaction parameter $a_{ij}$

Get the interaction parameter $b_{ij}$

Get the interaction parameter $c_{ij}$

Get index of the subgroup with id: subgroup_id

Get the subgroup’s maingroup

Get the subgroup’s $Q$ value

Get the subgroup’s $R$ value

Get the interaction parameter $a_{ij}$

Get the interaction parameter $b_{ij}$

Get the interaction parameter $c_{ij}$

Calculate the fluid composition based on an amount of addition of second fluid.

Calculate Zc, OMa and OMb from the delta_1 parameter.

Calculate residual Gibbs energy given volume and temperature.

Calculate the reduced residual Helmholtz Energy and it’s derivatives with the RKPR EOS

Linear interpolation.

K-factors regressión done by Wilson, used for initialization.

Combining rule that uses constant $k_{ij}$ values.

Combining rule that uses temperature dependant $k_{ij}$ values. With the following expression: $$k_{ij}(T) = k_{ij}^0 + k_{ij}^\infty \exp\left(\frac{-T}{T^*}\right)$$

Infinite pressure limit parameter $\Lambda$

Evaluate the Helmholtz derivatives with central finite difference.

Numeric $G^E$ model derivatives

Optimize the input function

Set a value to a default if it is not defined

Set a value to a default if it is not defined

PengRobinson76.

PengRobinson78.

PengRobinson 76 factory

PengRobinson 78 factory

Pressure calculation.

Solve pressure equality between two phases at a given temperature, total volume, vapor molar fractions and compositions.

Calculation of saturation pressure of a pure component using the secant method.

PT two-phase envelope calculation procedure.

Fugacity of a pure component

PX two-phase envelope calculation procedure.

Rachford-Rice equation for a two phase system

Residual Helmholtz model generic interface

RKPR Equation of State

RKPR $\delta_1$ parameter mixing rule.

Saturation pressure calculation function.

Saturation temperature calculation function.

Setup the basics variables that describe the model.

Instantiate a UNIFAC model

Instantiate a UNIQUAC model.

Get the size of the model.

SoaveRedlichKwong.

Solve the Rachford-Rice Equation.

Solve a linear sytem AX = b

Sort an array and return the indexes

…

SoaveRedlichKwong factory

Calculate the temperature dependence term of the UNIQUAC model.

Calculate the area fraciton of each froup on each molecule.

Michelsen’s modified $tpd$ function, $tm$.

Implementation of the $\psi(T)$ function of the UNIFAC model.

UNIFAC parameters

Cubic EoS volume initializer. For a Cubic Equation of State, the covolume calculated with the mixing rule is a good estimate for the initial volume solver on the liquid region.

ROUTINE FOR CALCULATION OF VOLUME, GIVEN PRESSURE

Solves volume roots using newton method. Given pressure and temperature.

Volume solver optimized for Cubic Equations of State.

Volume solver at a given pressure.

Calculation of lnphiP and derivatives rn mixture mole numbers (input) t temperature (k) (input) v volume (L) (input) p pressure (bar) (output) PHILOG vector of ln(phi(i)P) (output) 0 < INDIC < 5 DLPHIT t-derivative of ln(phi(i)) (const P, n) (output) 0 < INDIC = 2 or 4 DLPHIP P-derivative of ln(phi(i)) (const T, n) (output) 0 < INDIC < 5 FUGN comp-derivative of ln(phi(i)) (const t & P)(output) 2 < INDIC