Thermodynamic Properties in HYSYS for the Peng-Robinson Equation Property
Package
Physical properties are predicted by HYSYS using the following thermodynamic based
equations
V

H  H ID
1   P 
 Z 1
T

P



dV
RT
RT    T  V

V
ID
 1  P 
S  So
P
1
 ln Z  ln o    
  dV
RT
R  T  V V 
P

Where the Ideal Gas Enthalpy basis ( H ID ) used by HYSYS is equal to the ideal gas
Enthalpy of Formation at 25°C and 1 atm. The Ideal Gas Enthalpy basis ( H ID ) used by
HYSYS changes with temperature according to the coefficients on the Tdep tab for each
individual component.
(1)
(2)
An example of the prediction of the enthalpy of a single component is given below where
the values of a  f T  and b are from the Peng-Robinson equation of state.
H  H   Z  1 
ID
RT
1
1.5
2 bRT




da  V  2 0.5  1 b 

a  T dt  ln V  2 0.5  1 b 


(3)
where
a   xi x j ai a j  1  kij 
N
N
0.5
(4)
i 1 j 1
bi  0.077796
RTci
Pci
ai  aci i
aci  0.457235
(6)
RTci 2
Pci
  1  mi 1  Tri0.5 
mi  0.37646  1.54226 i  0.2699 i2
Section A.3 Enthalpy and Entropy, in the Simulation Basis Manual give the details of the
Property packages used by HYSYS.
To see these properties go to the Simulation Basis Manager and View the Peng-Robinson
Property package.
Select View and then select the components tab.
(5)
(7)
(8)
(9)
Select a component and look at the properties. These are snapshots from the TDep tab or
Temperature Dependent properties.
Note for volumetric flows: (See Simulation Basis A.5.2)
The volumetric flow rate reference state is defined as 60°F and 1 atm when using Field
units or 15°C and 1 atm when using SI units.