The Joule–Thomson effect describes the increase or decrease in the temperature of a real gas (as differentiated from an ideal gas) or a liquid when allowed to expand freely through a valve or other throttling device while kept insulated so that no heat is transferred to or from the fluid, and no external mechanical work is extracted from the fluid.[1] [2] [3] [4] The Joule–Thomson effect is an isenthalpic process, meaning that the enthalpy of the fluid is constant (i.e., does not change) during the process.