Joule-Thomson Inversion Temperatures

by Mike Favero

Submitted : Fall 2011

When gases are adiabatically expanded through a valve from high to low pressure their temperatures may either increase or decrease depending on the specific gas used, in this case Nitrogen (N₂). This may be determined by graphing the Temperature/Pressure correlation using the Joule-Thomson coefficient paired with the Van der Waals Equation to plot an inversion line. The line represents where the Joule-Thomson coefficient is equal to zero which is then used to accurately determine the regions where the gas is increasing or decreasing in temperature. Upon expansion inside the bounds of the line the gas will be decreasing in temperature, while outside it will be increasing. As temperatures were chosen the equation accurately displayed the correlating pressures creating an accurate inversion curve which can now be referenced too for future applications.

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