![]() ![]() In a free expansion, on the other hand, the gas does no work and absorbs no heat, so the internal energy is conserved.In this scenario, the gas does positive work during the expansion, and its temperature decreases. If the expansion process is reversible, meaning that the gas is in thermodynamic equilibrium at all times, it is called an isentropic expansion.The change in temperature experienced by the gas during expansion depends not only on the initial and final pressure, but also on the manner in which the expansion is carried out. The adiabatic (no heat exchanged) expansion of a gas may be carried out in a number of ways. It followed upon earlier work by Joule on Joule expansion, in which a gas undergoes free expansion in a vacuum and the temperature is unchanged, if the gas is ideal. The effect is named after James Prescott Joule and William Thomson, 1st Baron Kelvin, who discovered it in 1852. The throttling due to the flow resistance in supply lines, heat exchangers, regenerators, and other components of (thermal) machines is a source of losses that limits their performance. Throttling is a fundamentally irreversible process. In hydraulics, the warming effect from Joule–Thomson throttling can be used to find internally leaking valves as these will produce heat which can be detected by thermocouple or thermal-imaging camera. The gas-cooling throttling process is commonly exploited in refrigeration processes such as liquefiers in air separation industrial process. Most liquids such as hydraulic oils will be warmed by the Joule–Thomson throttling process. At room temperature, all gases except hydrogen, helium, and neon cool upon expansion by the Joule–Thomson process when being throttled through an orifice these three gases experience the same effect but only at lower temperatures. This procedure is called a throttling process or Joule–Thomson process. In thermodynamics, the Joule–Thomson effect (also known as the Joule–Kelvin effect or Kelvin–Joule effect) describes the temperature change of a real gas or liquid (as differentiated from an ideal gas) when it is forced through a valve or porous plug while keeping it insulated so that no heat is exchanged with the environment. For the concept in computing, see rate limiting. ![]()
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