Joule Inversion Temperatures for Some Simple Real Gases

ABSTRACT

In the present work we calculate inversion temperatures Ti, for some simple real gases (He, Ne, Ar, Kr and H2) in the case of a Joule expansion; that is, a free adiabatic expansion. These calculations are made by means of an intermolecular potential of the Lennard-Jones type (12, 6), slightly modified by using a Jagla linear ramp in the repulsive part of the potential. For the Helium we find a Ti in agreement with both previous calculations published by other authors and with experimental results. For Ne and Ar our results are also within the interval of values previously reported, and for Kr we also obtain a very high inversion temperature as some other authors. However, for H2 we find a Ti approximately twice to big than its estimated experimental value. This last calculation is corrected if we use a short ranged Lennard-Jones potential of the type (24, 12), obtaining a result in good agreement with the recognized experimental value.