Molecular simulation of Joule-Thomson inversion curves

A method to determine Joule-Thomson inversion curves, using isobaric-isothe rmal Monte Carlo molecular simulations, is presented. The usual experimenta l practice to obtain the locus of points in which the isenthalpic derivativ e of temperature with respect to pressure vanishes is to process volumetric data by means of thermodynamic relations. This experimental procedure requ ires the very precise measurement of volumetric properties at conditions up to five times the fluid's critical temperature and twelve times its critic al pressure. These harsh experimental conditions have hindered the publicat ion of data for even simple fluids and mixtures. By using molecular simulat ion, these problems may be circumvented, since the computational effort is roughly independent of the actual value of the pressure or the temperature. In general. Joule-Thomson inversion curves obtained by molecular simulatio n may be used either as an unambiguous test for equations of state in the s upercritical and high-pressure regions or for the prediction of real fluid behavior, should the potential be well known. Both applications are exempli fied for a Lennard-Jones fluid for which the complete inversion curve is ob tained.