Joule-Thomson Effect
| Formula / Notation | μ_JT = (∂T/∂P)_H |
|---|---|
| Also Known As | Joule-Kelvin effect, throttling expansion, JT effect, isenthalpic expansion |
What is Joule-Thomson Effect?
The Joule-Thomson effect (also called the Joule-Kelvin effect) describes the temperature change of a real gas when it is allowed to expand at constant enthalpy (throttling through a porous plug or valve). Most gases cool on expansion below their inversion temperature — this is the basis of refrigeration and gas liquefaction. Hydrogen and helium, however, warm on expansion at room temperature.
Formula & Notation
Other Names / Synonyms: Joule-Kelvin effect, throttling expansion, JT effect, isenthalpic expansion
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
The Joule-Thomson effect (also called the Joule-Kelvin effect) describes the temperature change of a real gas when it is allowed to expand at constant enthalpy (throttling through a porous plug or valve). Most gases cool on expansion below their inversion temperature — this is the basis of refrigeration and gas liquefaction. Hydrogen and helium, however, warm on expansion at room temperature.
Refrigeration and air conditioning systems. Industrial gas liquefaction (N₂, O₂, Ar, He). Linde process for air liquefaction. Joule-Thomson coolers in cryogenic equipment. Throttle valves in refrigeration cycles. Compressed gas cylinder behavior (temperature drop on release).
Rapid expansion of compressed gases: temperature drop can cause condensation of moisture. Oxygen-enriched atmospheres from JT cooling: fire hazard. Cryogenic systems: severe cold burns. Hydrogen JT at room temperature: warms — fire hazard if near ignition source.
The formula or notation for Joule-Thomson Effect is: μ_JT = (∂T/∂P)_H