DATA-DRIVEN TEMPERATURE-DEPENDENCE OF EOS PARAMETERS

Using three kinds of experimental data (p(c), V-c and T-c at the criti cal state or p(s), V-s(V) and V-s(L) at different temperatures for sat uration data) three parameters of the EOS may be directly determined a nd the temperature dependence of the parameters may be established fro m thermodynamic conditions of vapour-liquid critical point or vapour-l iquid phase equilibria respectively. The principle was demonstrated on the BACK EOS. Examples of argon and n-alkanes were used to demonstrat e the idea. It was found, that there are two parameter sets of the BAC K equation that satisfy the critical or saturation conditions for cert ain pure compounds. The BACK equation is able to reproduce experimenta l Z(c) values for compounds above Z(c) = 0.2764 (that is, for argon, m ethane, ethane), but it is improper for higher alkanes. In case of n-a lkanes we found that there is no simple function for T dependence of B ACK parameters. Parameter values obtained in the way demonstrated may be useful to give initial values for parameter estimation from experim ental (e.g., VLE) data. (C) 1997 Elsevier Science B.V.