250 lines
8.9 KiB
C++
250 lines
8.9 KiB
C++
/**
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* @file WaterProps.h
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* Header for a class used to house several approximation
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* routines for properties of water.
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* (see \ref thermoprops
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* and class \link Cantera::WaterProps WaterProps\endlink).
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*/
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// This file is part of Cantera. See License.txt in the top-level directory or
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// at https://cantera.org/license.txt for license and copyright information.
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#ifndef CT_WATERPROPS_H
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#define CT_WATERPROPS_H
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#include "cantera/base/ct_defs.h"
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namespace Cantera
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{
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class WaterPropsIAPWS;
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class PDSS_Water;
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/**
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* @defgroup relatedProps Electric Properties of Phases
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*
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* Computation of the electric properties of phases
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*
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* ### Treatment of the phase potential and the electrochemical potential of a species
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*
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* The electrochemical potential of species \f$k\f$ in a phase \f$p\f$, \f$ \zeta_k \f$,
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* is related to the chemical potential via the following equation,
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*
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* \f[
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* \zeta_{k}(T,P) = \mu_{k}(T,P) + z_k \phi_p
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* \f]
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*
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* where \f$ \nu_k \f$ is the charge of species \f$k\f$, and \f$ \phi_p \f$ is
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* the electric potential of phase \f$p\f$.
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*
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* The potential \f$ \phi_p \f$ is tracked and internally stored within the
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* base ThermoPhase object. It constitutes a specification of the internal state
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* of the phase; it's the third state variable, the first two being temperature
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* and density (or, pressure, for incompressible equations of state). It may be
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* set with the function, ThermoPhase::setElectricPotential(), and may be
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* queried with the function ThermoPhase::electricPotential().
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*
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* Note, the overall electrochemical potential of a phase may not be changed
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* by the potential because many phases enforce charge neutrality:
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*
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* \f[
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* 0 = \sum_k z_k X_k
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* \f]
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*
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* Whether charge neutrality is necessary for a phase is also specified within
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* the ThermoPhase object, by the function call
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* ThermoPhase::chargeNeutralityNecessary(). Note, that it is not necessary for
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* the IdealGas phase, currently. However, it is necessary for liquid phases
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* such as DebyeHuckel and HMWSoln for the proper specification of the chemical
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* potentials.
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*
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* This equation, when applied to the \f$ \zeta_k \f$ equation described
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* above, results in a zero net change in the effective Gibbs free energy of
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* the phase. However, specific charged species in the phase may increase or
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* decrease their electrochemical potentials, which will have an effect on
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* interfacial reactions involving charged species, when there is a potential
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* drop between phases. This effect is used within the InterfaceKinetics and
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* EdgeKinetics kinetics objects classes.
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*
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* ### Electrothermochemical Properties of Phases of Matter
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*
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* The following classes are used to compute the electrical and
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* electrothermochemical properties of phases of matter. The main property
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* currently is the dielectric constant, which is an important parameter for
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* electrolyte solutions. The class WaterProps calculate the dielectric
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* constant of water as a function of temperature and pressure.
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*
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* WaterProps also calculate the constant A_debye used in the Debye Huckel and
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* Pitzer activity coefficient calculations.
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*
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* @ingroup phases
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*/
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//@{
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//! The WaterProps class is used to house several approximation routines for
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//! properties of water.
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/*!
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* The class is also a wrapper around the WaterPropsIAPWS class which provides
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* the calculations for the equation of state properties for water.
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*
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* In particular, this class house routine for the calculation of the dielectric
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* constant of water
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*
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* Most if not all of the member functions are static.
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*/
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class WaterProps
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{
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public:
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//! Default constructor
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WaterProps();
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//! Constructor
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/*!
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* @param wptr Pointer to WaterPropsIAPWS object
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*/
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WaterProps(WaterPropsIAPWS* wptr);
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//! Constructor with pointer to Water PDSS object
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/*!
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* @param wptr Pointer to water standard state object
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*/
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WaterProps(PDSS_Water* wptr);
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// WaterProps objects are not copyable or assignable
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WaterProps(const WaterProps& b) = delete;
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WaterProps& operator=(const WaterProps& b) = delete;
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virtual ~WaterProps();
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//! Simple calculation of water density at atmospheric pressure.
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//! Valid up to boiling point.
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/*!
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* This formulation has no dependence on the pressure and shouldn't be used
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* where accuracy is needed.
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*
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* @param T temperature in kelvin
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* @param P Pressure in pascal
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* @param ifunc changes what's returned
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*
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* @return value returned depends on ifunc value:
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* - ifunc = 0 Returns the density in kg/m^3
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* - ifunc = 1 returns the derivative of the density wrt T.
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* - ifunc = 2 returns the 2nd derivative of the density wrt T
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* - ifunc = 3 returns the derivative of the density wrt P.
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*
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* Verification:
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* Agrees with the CRC values (6-10) for up to 4 sig digits.
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*
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* units = returns density in kg m-3.
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*/
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static doublereal density_T(doublereal T, doublereal P, int ifunc);
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//! Bradley-Pitzer equation for the dielectric constant
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//! of water as a function of temperature and pressure.
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/*!
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* Returns the dimensionless relative dielectric constant and its
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* derivatives.
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*
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* Range of validity: 0 to 350C, 0 to 1 kbar pressure
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*
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* @param T temperature (kelvin)
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* @param P_pascal pressure in pascal
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* @param ifunc changes what's returned from the function
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* @return Depends on the value of ifunc:
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* - ifunc = 0 return value
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* - ifunc = 1 return temperature derivative
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* - ifunc = 2 return temperature second derivative
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* - ifunc = 3 return pressure first derivative
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*
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* Validation: Numerical experiments indicate that this function agrees with
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* the Archer and Wang data in the CRC p. 6-10 to all 4 significant digits
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* shown (0 to 100C).
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*
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* value at 25C and 1 atm, relEps = 78.38
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*/
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doublereal relEpsilon(doublereal T, doublereal P_pascal, int ifunc = 0);
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//! ADebye calculates the value of A_Debye as a function of temperature and
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//! pressure according to relations that take into account the temperature
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//! and pressure dependence of the water density and dielectric constant.
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/*!
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* The A_Debye expression appears on the top of the ln actCoeff term in the
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* general Debye-Huckel expression It depends on temperature and pressure.
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* And, therefore, most be recalculated whenever T or P changes. The units
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* returned by this expression are sqrt(kg/gmol).
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*
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* \f[
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* A_{Debye} = \frac{1}{8 \pi} \sqrt{\frac{2 N_{Avog} \rho_w}{1000}}
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* {\left(\frac{e^2}{\epsilon k_{boltz} T}\right)}^{\frac{3}{2}}
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* \f]
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*
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* Nominal value at 25C and 1atm = 1.172576 sqrt(kg/gmol).
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*
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* Based on:
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* - epsilon/epsilon_0 = 78.54 (water at 25C)
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* - T = 298.15 K
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* - B_Debye = 3.28640E9 sqrt(kg/gmol)/m
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*
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* @param T Temperature (kelvin)
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* @param P pressure (pascal)
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* @param ifunc Changes what's returned from the routine
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* @returns a double whose meaning depends on ifunc:
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* - ifunc = 0 return value
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* - ifunc = 1 return temperature derivative
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* - ifunc = 2 return temperature second derivative
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* - ifunc = 3 return pressure first derivative
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*
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* Verification: With the epsRelWater value from the Bradley-Pitzer
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* relation, and the water density from the density_IAPWS() function, The
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* A_Debye computed with this function agrees with the Pitzer table p. 99 to
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* 4 significant digits at 25C. and 20C. (Aphi = ADebye/3)
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*/
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doublereal ADebye(doublereal T, doublereal P, int ifunc);
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//! Returns the saturation pressure given the temperature
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/*!
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* @param T temperature (kelvin)
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* @returns the saturation pressure (pascal)
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*/
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doublereal satPressure(doublereal T);
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//! Returns the density of water
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/*!
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* This function sets the internal temperature and pressure
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* of the underlying object at the same time.
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*
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* @param T Temperature (kelvin)
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* @param P pressure (pascal)
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*/
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doublereal density_IAPWS(doublereal T, doublereal P);
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//! Returns the density of water
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/*!
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* This function uses the internal state of the underlying water object
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*/
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doublereal density_IAPWS() const;
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//! returns the coefficient of thermal expansion
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/*!
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* @param T Temperature (kelvin)
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* @param P pressure (pascal)
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*/
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doublereal coeffThermalExp_IAPWS(doublereal T, doublereal P);
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//! Returns the isothermal compressibility of water
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/*!
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* @param T temperature in kelvin
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* @param P pressure in pascal
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*/
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doublereal isothermalCompressibility_IAPWS(doublereal T, doublereal P);
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protected:
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//! Pointer to the WaterPropsIAPWS object
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WaterPropsIAPWS* m_waterIAPWS;
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//! true if we own the WaterPropsIAPWS object
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bool m_own_sub;
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};
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//@}
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}
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#endif
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