fixed some conversion funcs, added new ones

src/HelperFunctions.jl

@@ -372,22 +372,48 @@ function density_to_molar_volume(density_g_cm3, mole_fractions, molecular_weight
     return molar_volume  # L / mol
 end
 
+# todo verify this 
+"Convert `CC(STP)/CC(polymer)`` to `g(penetrant)/g(polymer)`"
+function ccpen_per_ccpol_to_gpen_per_gpol(cc_per_cc, polymer_density_g_cm3, penetrant_molecular_weight)
+    return cc_per_cc / CC_PER_MOL_STP * penetrant_molecular_weight / polymer_density_g_cm3
+end
+
 "Convert polymer phase mass fractions to `g(penetrant)/g(polymer)`. Assumes that the polymer is the first item in the vector."
 function polymer_phase_mass_fractions_to_gpen_per_gpol(mass_fractions)
     return mass_fractions[2:end] ./ mass_fractions[1]
 end
 
-"Convert polymer phase mass fraction to CC(STP)/CC(polymer)."
+"Convert polymer phase mass fraction to CC(STP)/CC(polymer). Assumes that the polymer is the first item in the vector."
 function polymer_phase_mass_fractions_to_ccpen_per_ccpol(mass_fractions, polymer_density_g_cm3, penetrant_molecular_weights)
     # mass fractions includes the polymer
-    g_per_g = polymer_phase_mass_fractions_to_gpen_per_gpol(mass_fractions)
-    return g_per_g * CC_PER_MOL_STP * polymer_density_g_cm3 ./ penetrant_molecular_weights
-end
 
-# todo verify this 
-"Convert `CC(STP)/CC(polymer)`` to `g(penetrant)/g(polymer)`"
-function ccpen_per_ccpol_to_gpen_per_gpol(cc_per_cc, polymer_density_g_cm3, penetrant_molecular_weight)
-    return cc_per_cc / CC_PER_MOL_STP * penetrant_molecular_weight / polymer_density_g_cm3
+    mass_pol = mass_fractions[1]
+    mass_pens = mass_fractions[2:end]
+
+    vol_pol = mass_pol / polymer_density_g_cm3 # cm3
+    mol_pens = mass_pens ./ penetrant_molecular_weights # g / (g/mol) = mol
+
+    cc_pens = mol_pens .* CC_PER_MOL_STP # mol * cc(STP) /mol = cc(STP)
+    concs = cc_pens ./ vol_pol # CC/CC
+    return concs
+
+    # g_per_g = polymer_phase_mass_fractions_to_gpen_per_gpol(mass_fractions)
+    # return g_per_g * CC_PER_MOL_STP * polymer_density_g_cm3 ./ penetrant_molecular_weights
+end
+
+"Convert concentrations in CC(STP)/CC(polymer) to polymer phase mass fractions. The first index will be the polymer."
+function ccpen_per_ccpol_to_mass_fractions(cc_per_cc, polymer_density_g_cm3, penetrant_molecular_weights)
+    @assert length(cc_per_cc) == length(penetrant_molecular_weights)
+    # assume that x cc/cc is x CC STP per 1 cm3 of polymer
+    mol_pens = cc_per_cc ./ CC_PER_MOL_STP # cm3(stp) / (cm3(STP)/mol) = mol
+    mass_pens = mol_pens .* penetrant_molecular_weights # mol * g/mol = g
+    mass_poly = 1 * polymer_density_g_cm3
+    mass_system = sum(mass_pens) + mass_poly
+    mfracs = [mass_poly/mass_system; mass_pens ./ mass_system]
+    return mfracs
+
+    # mfrac_i = cc_per_cc .* penetrant_molecular_weights ./ (CC_PER_MOL_STP .* polymer_density_g_cm3)
+    # return [1-sum(mfrac_i); mfrac_i]
 end
 
 "Convert polymer density to specific volume, optionally with dilation."

src/MembraneBase.jl

@@ -46,6 +46,7 @@ module MembraneBase
     export density_to_molar_volume
     export polymer_phase_mass_fractions_to_gpen_per_gpol
     export polymer_phase_mass_fractions_to_ccpen_per_ccpol
+    export ccpen_per_ccpol_to_mass_fractions
     export polymer_specific_volume
 
     # isotherm methods

test/runtests.jl

@@ -76,6 +76,19 @@ using TaylorSeries
         recovered_mole_fractions = mass_fractions_to_mole_fractions(mass_fractions, molecular_weights)
         @test mole_fractions ≈ recovered_mole_fractions
 
+        rho = 1.1
+        mw = [11, 12, 13, 14, 15]
+        ccs_1 = [1, 2, 3, 4, 5]
+
+        mfracs = MembraneBase.ccpen_per_ccpol_to_mass_fractions(ccs_1, rho, mw)
+        recovered_concs = polymer_phase_mass_fractions_to_ccpen_per_ccpol(mfracs, rho, mw)
+        @test recovered_concs ≈ ccs_1
+
+        ccs_2 = 4
+        mfrac = MembraneBase.ccpen_per_ccpol_to_mass_fractions(ccs_2, rho, mw[4])
+        recovered_conc = polymer_phase_mass_fractions_to_ccpen_per_ccpol(mfrac, rho, mw[4])
+        @test ccs_2 ≈ recovered_conc[1]
+
         molar_volume = 0.228  # L/mol
         density = molar_volume_to_density(molar_volume, mole_fractions, molecular_weights)
         recovered_molar_volume = density_to_molar_volume(density, mole_fractions, molecular_weights)