For an ideal gas:

pv = RT

1.195

1.196

There is no change in temperature when an ideal gas is made to undergo a Joule-Thompson expansion.

For an incompressible fluid:

1.197

Thus an incompressible fluid is heated while undergoing throttling process.

Application of Joule-Thompson effect:

1. Vapor compression refrigeration system
2. Production of dry ice or solid CO₂ for low temperature refrigeration

Example:

Joule-Kelvin coefficient µ_j is a measure of the temperature change during a throttling process. A similar measure of temperature change produced by an isentropic change of pressure is provided by the coefficient µ_s where

Prove that:

Solution: The Joule –Kelvin coefficient µ_j is given by

Maxwell's Relations