Supporting Information: Isobaric Heat Capacity Measurements of Liquid
Methane + Propane, Methane + Butane and a Mixed Refrigerant by
Differential Scanning Calorimetry at High Pressures and Low
Temperatures
Tauqir H. Syed, Thomas J. Hughes, Kenneth N. Marsh, and Eric F. May*
Centre for Energy, School of Mechanical and Chemical Engineering, The University of
Western Australia, Crawley WA 6009, Australia.
Supporting Information
S.1 – AspenTech Hysys Peng-Robinison equation of state
Tables S1 to S3 contain parameters used within the Peng-Robinson equation of state as
implemented in AspenTech Hysys.
Table S1 Default critical temperatures, critical pressures and acentric factors from
AspenTech Hysys
Methane
Ethane
Propane
Butane
Nitrogen
Tc/K
190.699
305.428
369.898
425.199
126.194
Pc/kPa
4640.68
4883.85
4256.66
3796.62
3394.37
ω
1.15E-02
9.86E-02
0.1524
0.201
4.00E-02
Table S2 Default ideal gas heat capacity polynomial coefficients* from AspenTech Hysys
Methane
Ethane
Propane
Butane
Nitrogen
a
2.36459
1.1429
0.395
0.008541
0.982747
b
-4.26E-03
-6.47E-04
4.23E-03
6.55E-03
1.94E-04
c
1.70E-05
1.27E-05
1.19E-06
-3.33E-06
-1.25E-09
d
-1.49E-08
-1.36E-08
-2.67E-09
7.07E-10
-1.46E-11
e
4.30E-12
4.41E-12
8.40E-13
-3.20E-14
2.03E-15
Tmin/K
3.15
3.15
3.15
3.15
3.15
Tmax/K
5273.15
-1
5273.15
5273.15
5273.15
5273.15
-1
* The cp in kJ·kg ·K is calculated from the polynomial expression:
cp = a + bT + cT2 + dT3 + eT4
Table S3. Default binary interaction (kij) parameters from AspenTech Hysys for the PengRobinson equation of state
Methane
Ethane
Propane
Butane
Nitrogen
Methane
2.24E-03
6.83E-03
1.23E-02
3.60E-02
Ethane
2.24E-03
1.26E-03
4.10E-03
5.00E-02
Propane
6.83E-03
1.26E-03
8.19E-04
8.00E-02
Butane
1.23E-02
4.10E-03
8.19E-04
9.00E-02
Nitrogen
3.60E-02
5.00E-02
8.00E-02
9.00E-02
1
The default Peng-Robinson equation of state in AspenTech Hysys is represented by the
following equations:
p=
RT
aα
−
v − b v (v + b ) + b (v − b )
2


T 
2
with α =  1 + n  1 −
  and n = 0.37464 + 1.54226ω − 0.26992ω


TC  


Mixing rules:
N
N
i
j
amix = ∑∑ xi x j (1 − kij ) ai a j
N
bmix = ∑ xi bi
i
S.2 – REFPROP Peng-Robinson equation of state
The alpha function and the binary interaction parameters that REFPROP uses with its default
Peng-Robinson equation of state are inaccessible to the user. The sources of isobaric ideal
gas heat capacities and critical properties used in REFPROP for the components we studied
are listed in table S4.
Table S4 Sources of isobaric ideal gas heat capacity and critical properties used in
REFPROP’s default Peng-Robinson equation of state
Methane
Setzmann, U.; Wagner, W. A New Equation of State and Tables of
Thermodynamic Properties for Methane Covering the Range from the Melting
Line to 625 K at Pressures up to 1000 MPa. J. Phys. Chem. Ref. Data 1991, 20,
1061-1151
Ethane
Bücker, D.; Wagner, W. A Reference Equation of State for the
Thermodynamic Properties of Ethane for Temperatures from the Melting Line
to 675 K and Pressures up to 900 MPa. J. Phys. Chem. Ref. Data 2006, 35,
205-266
Propane
Lemmon, E. W.; McLinden, M. O.; Wagner, W. Thermodynamic Properties of
Propane. III. A Reference Equation of State for Temperatures from the Melting
Line to 650 K and Pressures up to 1000 MPa. J. Chem. Eng. Data 2009, 54,
3141-3180.
Butane
Bücker, D.; Wagner, W. Reference Equations of State for the Thermodynamic
Properties of Fluid Phase n-Butane and Isobutane. J. Phys. Chem. Ref. Data
2006, 35, 929-1019.
Nitrogen
Span, R.; Lemmon, E.W.; Jacobsen, R.T; Wagner, W.; Yokozeki, A. A
Reference Equation of State for the Thermodynamic Properties of Nitrogen for
Temperatures from 63.151 to 1000 K and Pressures to 2200 MPa. J. Phys.
Chem. Ref. Data 2000, 29, 1361-1433.
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