where aŋi, a∏, and a2⅛, as well as bθ2,b1,, and b2i, are the model (universal) constants.
The new EOS has a different hard chain term than the PC-SAFT equation of state;
therefore the first step was to obtain the universal constants from the experimental
data of n-alkanes, following the method proposed by Gross and Sadowski for the
estimation of the constants of the original PC-SAFT equation of state [48]. During
the regression process, it was found that the sensitivity of the model to the values of
b0i, bu and b2j was low, therefore the values of b0l, b∏ and b2, regressed by Gross and
Sadowski [48] were not changed. The аОг, a∏ and а2г constants were regressed using
the data for the n-alkane series from n-C3 to n-C10. The universal model constants
are reported in table 2.1. It should be noted that unlike the original work by Gross
and Sadowski [48], methane was not used during the regression. This is because the
chain length parameter of methane less than two. The hard chain term in SAFT-D
is undefined for values less than two, as it includes a contribution from dimerization.
The focus of this work being on long chain molecules and polymers, this problem is
not addressed here.
i |
________⅞o________ |
_______aɪ________ |
_______a2________ |
_______b0________ |
bɪ |
_______b2________ |
ɪ |
0.895225463 |
-0.286985055 |
-0.235561718 |
0.7240946941 |
-0.5755498075 |
0.0976883116 |
1 |
0.612099057 |
0.234102864 |
0.353133874 |
2.2382791861 |
0.6995095521 |
-0.2557574982 |
2 |
2.712198604 |
-2.562524895 |
0.743179541 |
-4.0025849485 |
3.8925673390 |
-9.1558561530 |
3 |
-19.524430960 |
7.405608026 |
8.195261945 |
-21.0035768150 |
-17.2154716480 |
20.6420759740 |
4 |
74.955546120 |
-20.362454500 |
-27.727172880 |
26.8556413630 |
192.6722644700 |
-38.8044300520 |
5 |
-142.408855200 |
50.431494580 |
28.062462310 |
206.5513384100 |
-161.8264616500 |
93.6267740770 |
6 |
118.084041300 |
-87.743797970 |
24.379172350 |
-355.6023561200 |
-165.2076934600 |
-29.6669055850 |
Table 2.1: Universal model constants. The values of ao, aɪ and a2 were adjusted in this
work; the values of bɑ, bɪ and b2 are from Gross and Sadowski [48].
47