C# wrapper help - Need to calculate Cricondentherm hydrocarbon dewpoint, Critical Pressure, Critical Temperature, Max Pressure

[prasadAnandaraman]

What is the best method to call to calculate Cricondentherm hydrocarbon dewpoint, Critical Pressure, Critical Temperature, Max Pressure? I need more info about the parameters. I have the following...
HYDROGEN;HELIUM;CO2;H2S;NITROGEN;OXYGEN;ARGON;METHANE;ETHANE;PROPANE;ISOBUTAN;BUTANE;NEOPENTN;IPENTANE;HEXANE;HEPTANE;OCTANE;NONANE;DECANE

[Matthew-Boyd]

Below is an example Python script you can modify for C#. Modify the mole fractions as appropriate--these are not standard values. Note that I'm using (n-)pentane instead of neopentane as it is more prevalent in natural gas. If you do wish to use the latter, then you can just substitute that.

import numpy as np
from ctREFPROP.ctREFPROP import REFPROPFunctionLibrary

RP = REFPROPFunctionLibrary(r"C:\Program Files (x86)\REFPROP")  # adjust path as needed
RP.SETPATHdll(r"C:\Program Files (x86)\REFPROP")

# GERG-2008 components in REFPROP fluid names
fluids = "HYDROGEN|HELIUM|CO2|H2S|NITROGEN|OXYGEN|ARGON|METHANE|ETHANE|PROPANE|ISOBUTANE|BUTANE|IPENTANE|PENTANE|HEXANE|HEPTANE|OCTANE|NONANE|DECANE"

# Mole fractions matching the order above
z = [
    0.0050,  # HYDROGEN
    0.0021,  # HELIUM
    0.0050,  # CO2
    0.0010,  # H2S
    0.0300,  # NITROGEN
    0.0005,  # OXYGEN
    0.0005,  # ARGON
    0.8500,  # METHANE
    0.0700,  # ETHANE
    0.0250,  # PROPANE
    0.0040,  # ISOBUTANE
    0.0040,  # BUTANE
    0.0008,  # IPENTANE
    0.0007,  # PENTANE
    0.0006,  # HEXANE
    0.0004,  # HEPTANE
    0.0002,  # OCTANE
    0.0001,  # NONANE
    0.0001,  # DECANE
]

assert abs(sum(z) - 1.0) < 1e-10, "Mole fractions must sum to 1.0"

# Set the mixture and use GERG-2008 equation of state
RP.FLAGSdll('GERG 2008', 1)     # 1 = use GERG-2008 model
RP.SETFLUIDSdll(fluids)
RP.SATSPLNdll(z)                # calculate phase boundary

# Calculate critical point
result = RP.CRITPdll(z)
print(f"T_critical = {result.Tc} [K]")
print(f"P_critical = {result.Pc * 1.e-3} [MPa]")
print(f"D_critical = {result.Dc} [mol/L]")

# Calculate cricondentherm and cricondenbar
iUnits = 1                      # 1 = MOLE SI
iMass = 0                       # 0 = molar basis
iFlag = 1                       # 1 = write labels and units
result = RP.ALLPROPSdll('TMAXT,PMAXT,DMAXT,TMAXP,PMAXP,DMAXP', iUnits, iMass, iFlag, 0, 0, z)    # see Table 1 in manual
print(f"T_cricondentherm = {result.Output[0]} [K]")
print(f"P_cricondentherm = {result.Output[1]} [MPa]")
print(f"D_cricondentherm = {result.Output[2]} [mol/L]")
print(f"T_cricondenbar = {result.Output[3]} [K]")
print(f"P_cricondenbar = {result.Output[4]} [MPa]")
print(f"D_cricondenbar = {result.Output[5]} [mol/L]")

T_critical = 221.2511662727773 [K]
P_critical = 8.079258592232971 [MPa]
D_critical = 12.33068581256604 [mol/L]
T_cricondentherm = 303.0555128508377 [K]
P_cricondentherm = 3.9459819211825593 [MPa]
D_cricondentherm = 1.7047984502317666 [mol/L]
T_cricondenbar = 260.81901211930943 [K]
P_cricondenbar = 10.557150526690775 [MPa]
D_cricondenbar = 7.687485911976723 [mol/L]

[prasadAnandaraman]

Thanks Mathew for your help. If I need to change the method to Perg-Robinson, what should I do?
Also, do I need to call CRITPdll? ALLpropsdll will give critical points also, correct?

[prasadAnandaraman]

When I provide this configuration thru the above code you have provided, it never gives me same results as you see in the picture. What am i doing wrong?