RedlichKwongMFTP.h

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//! @file RedlichKwongMFTP.h
 
// This file is part of Cantera. See License.txt in the top-level directory or
// at https://cantera.org/license.txt for license and copyright information.
 
#ifndef CT_REDLICHKWONGMFTP_H
#define CT_REDLICHKWONGMFTP_H
 
#include "MixtureFugacityTP.h"
#include "cantera/base/Array.h"
 
namespace Cantera
{
/**
 * Implementation of a multi-species Redlich-Kwong equation of state
 *
 * @ingroup thermoprops
 */
class RedlichKwongMFTP : public MixtureFugacityTP
{
public:
    //! Construct a RedlichKwongMFTP object from an input file
    /*!
     * @param infile Name of the input file containing the phase definition.
     *               If blank, an empty phase will be created.
     * @param id     name (ID) of the phase in the input file. If empty, the
     *               first phase definition in the input file will be used.
     */
    explicit RedlichKwongMFTP(const string& infile="", const string& id="");
 
    string type() const override {
        return "Redlich-Kwong";
    }
 
    //! @name Molar Thermodynamic properties
    //! @{
    double cp_mole() const override;
    double cv_mole() const override;
    //! @}
    //! @name Mechanical Properties
    //! @{
 
    //! Return the thermodynamic pressure (Pa).
    /*!
     *  Since the mass density, temperature, and mass fractions are stored,
     *  this method uses these values to implement the
     *  mechanical equation of state @f$ P(T, \rho, Y_1, \dots, Y_K) @f$.
     *
     * @f[
     *    P = \frac{RT}{v-b_{mix}} - \frac{a_{mix}}{T^{0.5} v \left( v + b_{mix} \right) }
     * @f]
     */
    double pressure() const override;
 
    //! @}
 
public:
 
    //! Returns the standard concentration @f$ C^0_k @f$, which is used to
    //! normalize the generalized concentration.
    /*!
     * This is defined as the concentration by which the generalized
     * concentration is normalized to produce the activity. In many cases, this
     * quantity will be the same for all species in a phase. Since the activity
     * for an ideal gas mixture is simply the mole fraction, for an ideal gas
     * @f$ C^0_k = P/\hat R T @f$.
     *
     * @param k Optional parameter indicating the species. The default is to
     *          assume this refers to species 0.
     * @return
     *   Returns the standard Concentration in units of m3 kmol-1.
     */
    double standardConcentration(size_t k=0) const override;
 
    //! Get the array of non-dimensional activity coefficients at the current
    //! solution temperature, pressure, and solution concentration.
    /*!
     * For all objects with the Mixture Fugacity approximation, we define the
     * standard state as an ideal gas at the current temperature and pressure of
     * the solution. The activities are based on this standard state.
     *
     * @param ac Output vector of activity coefficients. Length: m_kk.
     */
    void getActivityCoefficients(span<double> ac) const override;
 
    //! @name  Partial Molar Properties of the Solution
    //! @{
 
    void getChemPotentials(span<double> mu) const override;
    void getPartialMolarEnthalpies(span<double> hbar) const override;
    void getPartialMolarEntropies(span<double> sbar) const override;
    void getPartialMolarIntEnergies(span<double> ubar) const override;
    void getPartialMolarCp(span<double> cpbar) const override {
        throw NotImplementedError("RedlichKwongMFTP::getPartialMolarCp");
    }
    void getPartialMolarVolumes(span<double> vbar) const override;
    //! @}
 
public:
    //! @name Initialization Methods - For Internal use
    //!
    //! The following methods are used in the process of constructing
    //! the phase and setting its parameters from a specification in an
    //! input file. They are not normally used in application programs.
    //! To see how they are used, see importPhase().
    //! @{
 
    bool addSpecies(shared_ptr<Species> spec) override;
    void initThermo() override;
    void getSpeciesParameters(const string& name, AnyMap& speciesNode) const override;
 
    //! Set the pure fluid interaction parameters for a species
    /*!
     *  The "a" parameter for species *i* in the Redlich-Kwong model is assumed
     *  to be a linear function of temperature:
     *  @f[ a = a_0 + a_1 T @f]
     *
     *  @param species   Name of the species
     *  @param a0        constant term in the expression for the "a" parameter
     *      of the specified species [Pa-m^6/kmol^2]
     *  @param a1        temperature-proportional term in the expression for the
     *      "a" parameter of the specified species [Pa-m^6/kmol^2/K]
     *  @param b         "b" parameter in the Redlich-Kwong model [m^3/kmol]
     */
    void setSpeciesCoeffs(const string& species, double a0, double a1, double b);
 
    //! Set values for the interaction parameter between two species
    /*!
     *  The "a" parameter for interactions between species *i* and *j* is
     *  assumed by default to be computed as:
     *  @f[ a_{ij} = \sqrt(a_{i,0} a_{j,0}) + \sqrt(a_{i,1} a_{j,1}) T @f]
     *
     *  This function overrides the defaults with the specified parameters:
     *  @f[ a_{ij} = a_{ij,0} + a_{ij,1} T @f]
     *
     *  @param species_i   Name of one species
     *  @param species_j   Name of the other species
     *  @param a0          constant term in the "a" expression [Pa-m^6/kmol^2]
     *  @param a1          temperature-proportional term in the "a" expression
     *      [Pa-m^6/kmol^2/K]
     */
    void setBinaryCoeffs(const string& species_i,
                         const string& species_j, double a0, double a1);
    //! @}
 
protected:
    // Special functions inherited from MixtureFugacityTP
    double sresid() const override;
    double hresid() const override;
 
public:
    double liquidVolEst(double TKelvin, double& pres) const override;
    double densityCalc(double T, double pressure, int phase, double rhoguess) override;
    double dpdVCalc(double TKelvin, double molarVol, double& presCalc) const override;
 
    double isothermalCompressibility() const override;
    double thermalExpansionCoeff() const override;
    double soundSpeed() const override;
 
    //! Calculate dpdV and dpdT at the current conditions
    /*!
     *  These are stored internally.
     */
    void pressureDerivatives() const;
 
    //! Update the a and b parameters
    /*!
     *  The a and the b parameters depend on the mole fraction and the
     *  temperature. This function updates the internal numbers based on the
     *  state of the object.
     */
    void updateMixingExpressions() override;
 
    //! Calculate the a and the b parameters given the temperature
    /*!
     * This function doesn't change the internal state of the object, so it is a
     * const function.  It does use the stored mole fractions in the object.
     *
     * @param temp  Temperature (TKelvin)
     * @param aCalc (output)  Returns the a value
     * @param bCalc (output)  Returns the b value.
     */
    void calculateAB(double temp, double& aCalc, double& bCalc) const;
 
    // Special functions not inherited from MixtureFugacityTP
 
    double da_dt() const;
 
    void calcCriticalConditions(double& pc, double& tc, double& vc) const override;
 
    //! Prepare variables and call the function to solve the cubic equation of state
    int solveCubic(double T, double pres, double a, double b, span<double> Vroot) const;
 
protected:
    //! Form of the temperature parameterization
    /*!
     *  - 0 = There is no temperature parameterization of a or b
     *  - 1 = The a_ij parameter is a linear function of the temperature
     */
    int m_formTempParam = 0;
 
    //! Value of b in the equation of state
    /*!
     *  m_b is a function of the temperature and the mole fraction.
     */
    double m_b_current = 0.0;
 
    //! Value of a in the equation of state
    /*!
     *  a_b is a function of the temperature and the mole fraction.
     */
    double m_a_current = 0.0;
 
    vector<double> a_vec_Curr_;
    vector<double> b_vec_Curr_;
 
    Array2D a_coeff_vec;
 
    //! Explicitly-specified binary interaction parameters
    map<string, map<string, pair<double, double>>> m_binaryParameters;
 
    enum class CoeffSource { EoS, CritProps, Database };
    //! For each species, specifies the source of the a and b coefficients
    vector<CoeffSource> m_coeffSource;
 
    int NSolns_ = 0;
 
    double Vroot_[3] = {0.0, 0.0, 0.0};
 
    //! Temporary storage - length = m_kk.
    mutable vector<double> m_pp;
 
    // Partial molar volumes of the species
    mutable vector<double> m_partialMolarVolumes;
 
    //! The derivative of the pressure wrt the volume
    /*!
     * Calculated at the current conditions. temperature and mole number kept
     * constant
     */
    mutable double dpdV_ = 0.0;
 
    //! The derivative of the pressure wrt the temperature
    /*!
     *  Calculated at the current conditions. Total volume and mole number kept
     *  constant
     */
    mutable double dpdT_ = 0.0;
 
    //! Vector of derivatives of pressure wrt mole number
    /*!
     *  Calculated at the current conditions. Total volume, temperature and
     *  other mole number kept constant
     */
    mutable vector<double> dpdni_;
 
private:
    //! Omega constant for a -> value of a in terms of critical properties
    /*!
     *  this was calculated from a small nonlinear solve
     */
    static const double omega_a;
 
    //! Omega constant for b
    static const double omega_b;
 
    //! Omega constant for the critical molar volume
    static const double omega_vc;
};
}
 
#endif