Joule-Thomson effect

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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[edit]

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}\vert_{p=0} = ^0\!\!\phi = B_2(T) -T \frac{dB_2(T)}{dT}

Inversion temperature[edit]

[1] [2]


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