Joule-Thomson effect

The Joule-Thomson effect is also known as the Joule-Kelvin effect. This effect is present in non ideal gasses, where a change in temperature occurs upon expansion.

Joule-Thomson coefficient

The Joule-Thomson coefficient is given by

$\mu _{\mathrm {J} T}=\left.{\frac {\partial T}{\partial p}}\right\vert _{H}$

where T is the temperature, p is the pressure and H is the enthalpy.

In terms of heat capacities one has

$\mu _{\mathrm {J} T}C_{V}=-\left.{\frac {\partial E}{\partial V}}\right\vert _{T}$

and

$\mu _{\mathrm {J} T}C_{p}=-\left.{\frac {\partial H}{\partial p}}\right\vert _{T}$

In terms of the second virial coefficient at zero pressure one has

$\mu _{\mathrm {J} T}\vert _{p=0}=^{0}\!\!\phi =B_{2}(T)-T{\frac {dB_{2}(T)}{dT}}$

References

Related reading

• Thomas R. Rybolt "A virial treatment of the Joule and Joule-Thomson coefficients", Journal of Chemical Education 58 pp. 620-624 (1981)