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H_DEP_PR

 

H_DEP_PR (Tr, w, Z, B) returns the dimensionless enthalpy departure of a pure fluid according to the Peng-Robinson equation of state

 

where

Tr is reduced temperature

w is the acentric factor

Z is the compressibility factor

B is the second Peng-Robinson equation of state parameter

 

The dimensionless enthalpy departure is the difference in enthalpy between an ideal gas (designated with a superscript 0) and a real gas at the same temperature and pressure divided by (R Tc) where R is the gas constant and Tc is the critical temperature.

 

 

 

Note that Z is provided by functions Z_G_PR and Z_L_PR and B is provided by procedure AB_PR for pure fluids.

 

The enthalpy departure of a mixture cannot  be determined with this function since Tr for a mixture is not defined.  Using the Peng-Robinson equation for a mixture, the enthalpy departure for a mixture can be expressed:

 

 

 

Procedure AB_MIX_PR can be used to determine values of A and B for the mixture and functions Z_G_PR and Z_L_PR provide the value of Z for the mixture.  The value of da/dT for the mixture is provided by function DSADT_MIX_PR.    

 

Example:

 

     Tr=0.85

     Pr=0.5

     omega=0.05

     Call AB_PR(Tr, Pr, omega: A,B)

Z_G=Z_G_PR(A,B)

R=R#

Tc=190.6 [K] "methane"

     DELTAh=H_DEP_PR(Tr,omega,Z_G,B)*R*Tc

 

{Solution:

A=0.3391 

B=0.04576 

DELTAh=1608 [kJ/kmol]

omega=0.05 

Pr=0.5 

R=8.314 [kJ/kmol-K]

Tc=190.6 [K]

Tr=0.85 

Z_G=0.5748 

}

 

 

Peng-Robinson Index