It is a measure of the rate of change of temperature with respect to pressure during a constant enthalpy process.

Remember that in the throttling process the pressure always drops. So, the denominator is always negative in the equation. Hence, if the temperature of the fluid drops the Joule-Thomson coefficient is positive. Conversely, if the temperature of the fluid increases Joule-Thomson coefficient is negative.

It is a measure of the rate of change of temperature with respect to pressure during a constant enthalpy process.

Remember that in the throttling process the

pressure always drops. So, the denominator is always negative in the equation. Hence, if the temperature of the fluid drops the Joule-Thomson coefficient is positive. Conversely, if the temperature of the fluid increases Joule-Thomson coefficient is negative.