Select thermodynamic models for process simulation
A Practical Guide to a Three Steps Methodology

Example 3-4: Quality evaluation of vapourisation enthalpy correlations

A comparison of enthalpy of vaporisation for two hydrocarbons is to be proposed. Differences between different correlations will be analysed. The various equations are the following:

DIPPR form:


Yaws form:


PPDS form:


Watson’s form:


In these relationships, the reduced temperature is defined as:image and the parameter τ is deduced from: image. Coefficients for the different equations are:

Table 1: Parameters for various enthalpy of vaporisation for pentane
Equation Tc (K) A B C D E
DIPPR 469.67 39.109 0.38681 0 0 0
Yaws 470.08 39.1846 0.388985 - - -
Table 2: Parameters for various enthalpy of vaporisation for benzene
Equation Tc (K) A B C D E
DIPPR 562.05 45.346 0.39053 0 0 0
PPDS 562.05 0.00171484 0.0258604 -0.0243564 0.00740881 0.00680068

For the Watson equation, we can take image= 33.6 kJ/mol at T0 =300K for benzene.



See complete results in file (xls):

Some help on nomenclature and tips to use this file can be found here.

A graph is constructed with the relative difference obtained by the various polynomials and compared against the DIPPR equation. The deviations between these different relations are weak and for this kind of compound are in agreement with the experimental deviation.

image Figure 1: Enthalpy of vaporisation of pentane and benzene as a function of temperature.


R. L. Rowley, W. V. Wilding, J. L. Oscarson, Y. Yang, N. A. Zundel, T. E. Daubert, R. P. Danner, DIPPR® Data Compilation of Pure Compound Properties, Design Institute for Physical Properties, AIChE, New York, NY (2003).