Joule-Thomson effect

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The Joule-Thomson effect is also known as the Joule-Kelvin effect.

Joule-Thomson coefficient

The Joule-Thomson coefficient is given by

\mu_{\mathrm JT} = \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 JT} C_V = -\left. \frac{\partial E}{\partial V} \right\vert_T


\mu_{\mathrm JT} 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 JT} = B_2 -T \frac{dB_2}{dT}


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