Thiele hard sphere equation of state

The Thiele hard sphere equation of state is an equation of state for a hard sphere fluid developed by Thiele in 1963. The equation provides a better approximation of the repulsive forces between molecules than the Van der Waals repulsive term. The equation is given below:

$Z_{hs}={\frac {p_{hs}V_{m}}{RT}}={\frac {1-\eta ^{3}}{(1-\eta )^{4}}}={\frac {1+\eta +\eta ^{2}}{(1-\eta )^{3}}}$,

where:

$Z_{hs}$ is the compressibility factor of the hard sphere fluid;

$p_{hs}$ is the pressure of the fluid;

$V_{m}$ is the molar volume of the fluid;

$T$ is the absolute temperature of the fluid;

$R$ is the gas constant; and

$\eta$ is the packing fraction of the fluid.

In terms of accuracy, the Thiele equation is superseded by the Carnahan-Starling equation of state