n - PATh :.: Process and Product Applied Thermodynamics research ...

Modeling
The mixture parameters a and b are calculated from the parameters of the pure
components aii and bii using the one fluid van der Waals mixing rules
∑∑
a z z a
(III.37)
= i j
∑
= i
i
j
ij
b zibi
(III.38)
where zi is the phase mole fraction of component i. The combining rule used for a is
( )( ) 2 / 1
k a a
aij = 1− ij ii jj
(III.39)
The kij is an adjustable parameter for each binary mixture. The kij´s fitted to the
experimental solubility data obtained in this work for O2/n-perfluoroalkanes, show strong
temperature dependence mainly for perfluoro-n-hexane and perfluoro-n-heptane where a
quadratic equation of the type
k ij
B C
= A + +
(III.40)
2
T T
had to be used in order to correctly describe the experimental data (Coutinho et al.,
1994).The coefficients A, B and C for the systems studied in this work are given in
Table III.4.
Table III.4. Coefficients for Equation III.40 and Average Binary Interaction Parameters, for all the
Temperatures. AAD is the Corresponding Average Absolute Errors for Binary Oxygen-
Perfluoroalkane Mixtures When an Averaged k is Used
ij
System A B C k AAD %
ij
O2 – C6F14
O2 – C7F16
3.66 x 10 1
2.20 x 10 1
-2.08 x 10 4
-1.26 x 10 4
2.94 x 10 6
1.80 x 10 6
0.122 12.35
0.091 10.07
O2 – C8F18 0.658 -196.42 -- 0.004 2.64
O2 – C9F20 0.481 -165.10 -- -0.073 2.95
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