Contents

Index

Volume-Temperature Based Properties

Clapeyron.pressure — Function
pressure(model::EoSModel, V, T, z=SA[1.])

default units: [Pa]

Returns the pressure of the model at a given volume, temperature and composition, defined as:

p = -∂A/∂V
Clapeyron.second_virial_coefficient — Function
second_virial_coefficient(model::EoSModel, T, z=SA[1.])

Default units: [m^3]

Calculates the second virial coefficient B, defined as:

B = lim(V->∞)[ V^2/RT *  (∂Aᵣ∂V + V*∂²Aᵣ∂V²) ]

where Aᵣ is the residual helmholtz energy.

Clapeyron.pip — Function
pip(model::EoSModel,V,T,z=[1.0])

Phase identification parameter Π. as described in 1. If Π > 1, then the phase is clasified as a liquid or a liquid-like vapor, being a vapor or vapor-like liquid otherwise.

This identification parameter fails at temperatures and pressures well aboVe the critical point.

Calculated as:

Π = V*((∂²p/∂V∂T)/(∂p/∂T) - (∂²p/∂V²)/(∂p/∂V))
  1. G. Venkatarathnama, L.R. Oellrich, Identification of the phase of a fluid using partial derivatives of pressure, volume,and temperature without reference to saturation properties: Applications in phase equilibria calculations, Fluid Phase Equilibria 301 (2011) 225–233

Pressure-Temperature Based Bulk Properties

In general almost all bulk properties follow the pattern:

function property(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)
    V = volume(model, p, T, z; phase, threaded, vol0)
    return VT_property(model,V,T,z)
end

So, you can calculate the property with Volume-Temperature variables by calling VT_property(model,V,T,z). Another way to do this is by using units, provided by Unitful.jl:

using Unitful
r = 18u"kg/m^3"
T = 373.15"K"
prop = helmholtz_free_energy(model,r,T,z,output = u"kJ")

Where r could be any molar or mass density, molar or mass volume, total volume or pressure. It also supports mass and mol amounts defined as units for the composition (z) If no units are provided for the composition, they will be considered moles.

Methods that require first order VT derivatives

Clapeyron.volume — Function
volume(model::EoSModel, p, T, z=SA[1.0]; phase=:unknown, threaded=true, vol0=nothing)

Calculates the volume (m³) of the compound modelled by model at a certain pressure, temperature and moles. phase is a Symbol that determines the initial volume root to look for:

  • If phase =:unknown (Default), it will return the physically correct volume root with the least gibbs energy.
  • If phase =:liquid, it will return the volume of the phase using a liquid initial point.
  • If phase =:vapor, it will return the volume of the phase using a gas initial point.
  • If phase =:solid, it will return the volume of the phase using a solid initial point (only supported for EoS that support a solid phase)
  • If phase =:stable, it will return the physically correct volume root with the least gibbs energy, and perform a stability test on the result.

All volume calculations are checked for mechanical stability, that is: dP/dV <= 0.

The calculation of both volume roots can be calculated in serial (threaded=false) or in parallel (threaded=true).

An initial estimate of the volume vol0 can be optionally be provided.

Tip

The volume computation may fail and return NaN because the default initial point is too far from the actual volume. Providing a value for vol0 may help in these situations. Such a starting point can be found from physical knowledge, or by computing the volume using a different model for example.

Stability checks

The stability check is disabled by default. that means that the volume obtained just follows the the relation P = pressure(model,V,T,z). For single component models, this is alright, but phase splits (with different compositions that the input) can and will occur, meaning that the volume solution does not correspond to an existing phase. For unknown multicomponent mixtures, it is recommended to use a phase equilibrium procedure (like tp_flash) to obtain a list of valid compositions, and then perform a volume calculation over those compositions. You can also pass phase=:stable to perform the stability test inside the volume solver. Finally, you can perform the stability test after the volume solver:

v = volume(model,p,T,z)
isstable(model,v,T,z)
Clapeyron.helmholtz_free_energy — Function
helmholtz_free_energy(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the helmholtz free energy, defined as:

A = eos(model,V(p),T,z)

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_helmholtz_free_energy(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.helmholtz_free_energy_res — Function
helmholtz_free_energy_res(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the residual helmholtz free energy, defined as:

A = eos_res(model,V(p),T,z)

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_helmholtz_free_energy_res(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.molar_density — Function
molar_density(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

default units: [mol/m^3]

Calculates the molar density, defined as:

ρₙ = ∑nᵢ/V

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_molar_density(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.mass_density — Function
mass_density(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true)

default units: [kg/m^3]

Calculates the mass density, defined as:

ρₙ = Mr/V

Where Mr is the molecular weight of the model at the input composition.

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_mass_density(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.compressibility_factor — Function
compressibility_factor(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Calculates the compressibility factor Z, defined as:

Z = p*V(p)/R*T

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.gibbs_free_energy — Function
gibbs_free_energy(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the gibbs free energy, defined as:

G = A + p*V

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_gibbs_free_energy(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.gibbs_free_energy_res — Function
gibbs_free_energy_res(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the residual gibbs free energy, defined as:

G = Ar - V*∂Ar/∂V

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_gibbs_free_energy_res(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.entropy — Function
entropy(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J/K]

Calculates entropy, defined as:

S = -∂A/∂T

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_entropy(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.entropy_res — Function
entropy_res(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J/K]

Calculates residual entropy, defined as:

S = -∂Ares/∂T

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_entropy_res(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.enthalpy — Function
enthalpy(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the enthalpy, defined as:

H = A - T * ∂A/∂T - V * ∂A/∂V

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_enthalpy(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.internal_energy — Function
internal_energy(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the internal energy, defined as:

U = A - T * ∂A/∂T

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_internal_energy(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.internal_energy_res — Function
internal_energy_res(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J]

Calculates the residual internal energy, defined as:

U = Ar - T * ∂Ar/∂T

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_internal_energy_res(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Methods that require second order VT derivatives

Clapeyron.isochoric_heat_capacity — Function
isochoric_heat_capacity(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J/K]

Calculates the isochoric heat capacity, defined as:

Cv = -T * ∂²A/∂T²

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_isochoric_heat_capacity(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Accurate ideal model required

This property requires at least second order ideal model temperature derivatives. If you are computing these properties, consider using a different ideal model than the BasicIdeal default (e.g. EoS(["species"];idealmodel = ReidIdeal)).

Clapeyron.isobaric_heat_capacity — Function
isobaric_heat_capacity(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J/K]

Calculates the isobaric heat capacity, defined as:

Cp = -T*(∂²A/∂T² - (∂²A/∂V∂T)^2 / ∂²A/∂V²)

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_isobaric_heat_capacity(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Accurate ideal model required

This property requires at least second order ideal model temperature derivatives. If you are computing these properties, consider using a different ideal model than the BasicIdeal default (e.g. EoS(["species"];idealmodel = ReidIdeal)).

Clapeyron.isothermal_compressibility — Function
isothermal_compressibility(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

default units: [Pa^-1]

Calculates the isothermal compressibility, defined as:

κT = (V*∂p/∂V)^-1

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_isothermal_compressibility(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.isentropic_compressibility — Function
isentropic_compressibility(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

default units: [Pa^-1]

Calculates the isentropic compressibility, defined as:

κS = (V*( ∂²A/∂V² - ∂²A/∂V∂T^2 / ∂²A/∂T² ))^-1

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_isentropic_compressibility(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Accurate ideal model required

This property requires at least second order ideal model temperature derivatives. If you are computing these properties, consider using a different ideal model than the BasicIdeal default (e.g. EoS(["species"];idealmodel = ReidIdeal)).

Clapeyron.speed_of_sound — Function
speed_of_sound(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

default units: [m/s]

Calculates the speed of sound, defined as:

c = V * √(∂²A/∂V² - ∂²A/∂V∂T^2 / ∂²A/∂T²)/Mr)

Where Mr is the molecular weight of the model at the input composition.

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_speed_of_sound(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Accurate ideal model required

This property requires at least second order ideal model temperature derivatives. If you are computing these properties, consider using a different ideal model than the BasicIdeal default (e.g. EoS(["species"];idealmodel = ReidIdeal)).

Clapeyron.isobaric_expansivity — Function
isobaric_expansivity(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

default units: [K^-1]

Calculates the isobaric expansivity, defined as:

α = -∂²A/∂V∂T / (V*∂²A/∂V²)

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_isobaric_expansivity(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.joule_thomson_coefficient — Function
joule_thomson_coefficient(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

default units: [K/Pa]

Calculates the joule thomson coefficient, defined as:

μⱼₜ = -(∂²A/∂V∂T - ∂²A/∂V² * ((T*∂²A/∂T² + V*∂²A/∂V∂T) / (T*∂²A/∂V∂T + V*∂²A/∂V²)))^-1

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_joule_thomson_coefficient(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Accurate ideal model required

This property requires at least second order ideal model temperature derivatives. If you are computing these properties, consider using a different ideal model than the BasicIdeal default (e.g. EoS(["species"];idealmodel = ReidIdeal)).

Methods that require first order composition derivatives

Clapeyron.chemical_potential — Function
chemical_potential(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J/mol]

Calculates the chemical potential, defined as:

μᵢ = ∂A/∂nᵢ

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_chemical_potential(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.chemical_potential_res — Function
chemical_potential_res(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Default units: [J/mol]

Calculates the residual chemical potential, defined as:

μresᵢ = ∂Ares/∂nᵢ

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_chemical_potential_res(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Clapeyron.fugacity_coefficient — Function
fugacity_coefficient(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)

Calculates the fugacity coefficient φᵢ, defined as:

log(φᵢ) = μresᵢ/RT - log(Z)

Where μresᵢ is the vector of residual chemical potentials and Z is the compressibility factor.

Internally, it calls Clapeyron.volume to obtain V and calculates the property via VT_fugacity_coefficient(model,V,T,z).

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Mixing

Clapeyron.mixing — Function
mixing(model::EoSModel, p, T, z=SA[1.], property; phase=:unknown, threaded=true, vol0=nothing)

Calculates the mixing function for a specified property as:

f_mix = f(p,T,z) - ∑zᵢ*f_pureᵢ(p,T)

The keywords phase, threaded and vol0 are passed to the Clapeyron.volume solver.

Initial guess functions

Clapeyron.lb_volume — Function
lb_volume(model::EoSModel,z=SA[1.0])

Returns the lower bound volume. It has different meanings depending on the Equation of State, but symbolizes the minimum allowable volume at a certain composition:

  • SAFT EoS: the packing volume
  • Cubic EoS, covolume (b) parameter

On empiric equations of state, the value is chosen to match the volume of the conditions at maximum pressure and minimum temperature , but the equation itself normally can be evaluated at lower volumes. On SAFT and Cubic EoS, volumes lower than lb_volume will likely error. The lower bound volume is used for guesses of liquid volumes at a certain pressure, saturated liquid volumes and critical volumes.

Clapeyron.T_scale — Function
T_scale(model::EoS,z=SA[1.0])

Represents a temperature scaling factor. On any EoS based on Critical parameters (Cubic or Empiric EoS), the temperature scaling factor is chosen to be the critical temperature. On SAFT or other molecular EoS, the temperature scaling factor is chosen to be a function of the potential depth ϵ. Used as scaling factors in saturation_pressure and as input for solving crit_pure

Clapeyron.p_scale — Function
p_scale(model::SAFTModel,z=SA[1.0])

Represents a pressure scaling factor On any EoS based on Critical parameters (Cubic or Empiric EoS), the pressure scaling factor is chosen to be a function of the critical pressure. On SAFT or other molecular EoS, the temperature scaling factor is chosen to a function of ∑(zᵢϵᵢ(σᵢᵢ)³) Used as scaling factors in saturation_pressure and as input for solving crit_pure

Clapeyron.x0_volume — Function
x0_volume(model,p,T,z; phase = :unknown)

Returns an initial guess of the volume at a pressure, temperature, composition and suggested phase. If the suggested phase is :unknown or :liquid, calls x0_volume_liquid. If the suggested phase is :gas, calls x0_volume_gas. If the suggested phase is solid, calls x0_volume_solid. Returns NaN otherwise

Clapeyron.x0_volume_solid — Function
x0_volume_solid(model,T,z)
x0_volume_solid(model,p,T,z)

Returns an initial guess to the solid volume, dependent on temperature and composition. needs to be defined for EoS that support solid phase. by default returns NaN. can be overrided if the EoS defines is_solid(::EoSModel) = true

Clapeyron.x0_volume_liquid — Function
x0_volume_liquid(model,T,z)
x0_volume_liquid(model,p,T,z)

Returns an initial guess to the liquid volume, dependent on temperature and composition. by default is 1.25 times lb_volume.

Clapeyron.x0_volume_gas — Function
x0_volume_gas(model,p,T,z)

Returns an initial guess to the gas volume, depending of pressure, temperature and composition. by default uses volume_virial

Clapeyron.volume_virial — Function
volume_virial(model::EoSModel,p,T,z=SA[1.0])
volume_virial(B::Real,p,T,z=SA[1.0])

Calculates an aproximation to the gas volume at specified pressure, volume and composition, by aproximating:

Z(v) ≈ 1 + B(T)/v

where Z is the compressibility factor and B is the second virial coefficient. If B>0, (over the inversion temperature) returns NaN. If the solution to the problem is complex (Z = 1 + B/v implies solving a quadratic polynomial), returns -2*B. If you pass an EoSModel as the first argument, B will be calculated from the EoS at the input T. You can provide your own second virial coefficient instead of a model.

Clapeyron.x0_sat_pure — Function
x0_sat_pure(model::EoSModel,T)

Returns a 2-tuple corresponding to (Vₗ,Vᵥ), where Vₗ and Vᵥ are the liquid and vapor initial guesses. Used in saturation_pressure methods that require initial volume guesses. It can be overloaded to provide more accurate estimates if necessary.

Clapeyron.x0_psat — Function
x0_psat(model::EoSModel, T,crit = nothing)

Initial point for saturation pressure, given the temperature and V,T critical coordinates. On moderate pressures it will use a Zero Pressure initialization. On pressures near the critical point it will switch to spinodal finding. Used in saturation_pressure methods that require initial pressure guesses. if the initial temperature is over the critical point, it returns NaN. It can be overloaded to provide more accurate estimates if necessary.

Clapeyron.antoine_coef — Function
antoine_coef(model)

should return a 3-Tuple containing reduced Antoine Coefficients. The Coefficients follow the correlation:

lnp̄ = log(p / p_scale(model))
T̃ = T/T_scale(model)
lnp̄ = A - B/(T̄ + C))

By default returns nothing. This is to use alternative methods in case Antoine coefficients aren't available. Used mainly in single and multicomponent temperature calculations.

Clapeyron.x0_crit_pure — Function
x0_crit_pure(model::EoSModel)

Returns a 2-tuple corresponding to (k,log10(Vc0)), where k is Tc0/T_scale(model,z)