Merge branch 'master' of https://github.com/ypaul21/Clapeyron.jl

docs/src/properties/bulk.md

@@ -62,6 +62,7 @@ Clapeyron.internal_energy_res
 ```@docs
 Clapeyron.isochoric_heat_capacity
 Clapeyron.isobaric_heat_capacity
+Clapeyron.adiabatic_index
 Clapeyron.isothermal_compressibility
 Clapeyron.isentropic_compressibility
 Clapeyron.speed_of_sound

src/methods/VT.jl

@@ -84,6 +84,14 @@ function VT_isobaric_heat_capacity(model::EoSModel, V, T, z=SA[1.])
     return -T*(∂²A∂T² - ∂²A∂V∂T^2/∂²A∂V²)
 end
 
+function VT_adiabatic_index(model::EoSModel, V, T, z=SA[1.])
+    d²A = f_hess(model,V,T,z)
+    ∂²A∂V∂T = d²A[1,2]
+    ∂²A∂V² = d²A[1,1]
+    ∂²A∂T² = d²A[2,2]
+    return 1 - ∂²A∂V∂T*∂²A∂V∂T/(∂²A∂V²*∂²A∂T²)
+end
+
 function VT_isothermal_compressibility(model::EoSModel, V, T, z=SA[1.])
     p0,∂p∂V = p∂p∂V(model,V,T,z)
     return -1/V/∂p∂V

src/methods/differentials.jl

@@ -10,7 +10,7 @@
 returns `f` and `∂f/∂T` at constant total volume and composition, where f is the total helmholtz energy, given by `eos(model,V,T,z)`
 
 """
-function ∂f∂T(model,V,T,z=SA[1.0])
+function ∂f∂T(model,V,T,z)
     f(∂T) = eos(model,V,∂T,z)
     return Solvers.derivative(f,T)
 end
@@ -21,9 +21,8 @@ end
 returns `f` and `∂f/∂V` at constant temperature and composition, where f is the total helmholtz energy, given by `eos(model,V,T,z)`, and V is the total volume
 """
 function ∂f∂V(model,V,T,z)
-    f(∂V) = a_res(model,∂V,T,z)
-    dadv = Solvers.derivative(f,V)
-    return Rgas(model)*T*(dadv - sum(z)/V)
+    f(∂V) = eos(model,∂V,T,z)
+    return Solvers.derivative(f,V)
 end
 
 #returns a tuple of the form ([∂f∂V,∂f∂T],f),using the least amount of computation

src/methods/pT.jl

@@ -275,6 +275,31 @@ function isobaric_heat_capacity(model::EoSModel, p, T, z=SA[1.]; phase=:unknown,
     V = volume(model, p, T, z; phase, threaded, vol0)
     return VT_isobaric_heat_capacity(model,V,T,z)
 end
+
+"""
+    adiabatic_index(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)
+
+Default units: `[J/K]`
+
+Calculates the isobaric heat capacity, defined as:
+
+```julia
+γ = Cp/Cv
+```
+Internally, it calls [`Clapeyron.volume`](@ref) to obtain `V` and
+calculates the property via `VT_adiabatic_index(model,V,T,z)`.
+
+The keywords `phase`, `threaded` and `vol0` are passed to the [`Clapeyron.volume`](@ref) solver.
+
+!!! warning "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)`).
+
+"""
+function adiabatic_index(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)
+    V = volume(model, p, T, z; phase, threaded, vol0)
+    return VT_adiabatic_index(model,V,T,z)
+end
+
 """
     isothermal_compressibility(model::EoSModel, p, T, z=SA[1.]; phase=:unknown, threaded=true, vol0=nothing)
 
@@ -762,7 +787,7 @@ end
 export entropy, internal_energy, enthalpy, gibbs_free_energy, helmholtz_free_energy
 export entropy_res, internal_energy_res, enthalpy_res, gibbs_free_energy_res, helmholtz_free_energy_res
 #second derivative order properties
-export isochoric_heat_capacity, isobaric_heat_capacity
+export isochoric_heat_capacity, isobaric_heat_capacity,adiabatic_index
 export isothermal_compressibility, isentropic_compressibility, speed_of_sound
 export isobaric_expansivity, joule_thomson_coefficient, inversion_temperature
 #higher derivative order properties

test/test_methods_eos.jl

@@ -5,6 +5,7 @@ using Clapeyron, Test, Unitful
     system = PCSAFT(["ethanol"])
     p = 1e5
     T = 298.15
+    T2 = 373.15
     @testset "Bulk properties" begin
         @test Clapeyron.volume(system, p, T) ≈ 5.907908736304141e-5 rtol = 1e-6
         @test Clapeyron.volume(system, p, T;phase=:v) ≈ 0.020427920501436134 rtol = 1e-6
@@ -20,6 +21,9 @@ using Clapeyron, Test, Unitful
         @test Clapeyron.helmholtz_free_energy(system, p, T) ≈ -18329.785451419295 rtol = 1E-6
         @test Clapeyron.isochoric_heat_capacity(system, p, T) ≈ 48.37961296309505 rtol = 1E-6
         @test Clapeyron.isobaric_heat_capacity(system, p, T) ≈ 66.45719988319257 rtol = 1E-6
+        Cp = Clapeyron.isobaric_heat_capacity(system, p, T2)
+        Cv = Clapeyron.isochoric_heat_capacity(system, p, T2)
+        @test Clapeyron.adiabatic_index(system, p, T2) ≈ Cp/Cv rtol = 1E-12
         @test Clapeyron.isothermal_compressibility(system, p, T) ≈ 1.1521981407243432e-9 rtol = 1E-6
         @test Clapeyron.isentropic_compressibility(system, p, T) ≈ 8.387789464951438e-10 rtol = 1E-6
         @test Clapeyron.speed_of_sound(system, p, T) ≈ 1236.4846683094133 rtol = 1E-6 #requires that the model has Mr