The Siemens cycle is a technique used to cool or liquefy gases

Liquefaction of gases

Liquefaction of gases includes a number of phases used to convert a gas into a liquid state. The processes are used for scientific, industrial and commercial purposes. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide, require...

.. A gas

Gas

Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 is compressed, leading to an increase in its temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 (by Gay-Lussac's law relating pressure and temperature

Gay-Lussac's law

The expression Gay-Lussac's law is used for each of the two relationships named after the French chemist Joseph Louis Gay-Lussac and which concern the properties of gases, though it is more usually applied to his law of combining volumes, the first listed here...

). The compressed gas is then cooled by a heat exchanger

Heat exchanger

A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

, then the cool, compressed gas is allowed to decompress, further cooling it (again by Gay-Lussac's law). This results in a gas (or liquefied gas) that is colder than the original and at the same pressure.

Carl Wilhelm Siemens

Carl Wilhelm Siemens

Carl Wilhelm Siemens was a German born engineer who for most of his life worked in Britain and later became a British subject.-Biography:...

 patented the Siemens cycle in 1857.

See also

• Adiabatic process
  Adiabatic process
  In thermodynamics, an adiabatic process or an isocaloric process is a thermodynamic process in which the net heat transfer to or from the working fluid is zero. Such a process can occur if the container of the system has thermally-insulated walls or the process happens in an extremely short time,...
  
  
• Gas compressor
  Gas compressor
  A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
  
  
• Hampson-Linde cycle
  Hampson-Linde cycle
  The Hampson–Linde cycle is based on the Joule-Thomson effectand is used in the liquefaction of gases. W. Hampson and Carl von Linde independently filed for patent of the cycle in 1895.-External links:*...
  
  
• Regenerative cooling
  Regenerative cooling
  Regenerative cooling in rockets is where some or all of the propellant is passed through tubes, channels or otherwise in a jacket around the combustion chamber or nozzle to cool the engine because the fuel in particular and sometimes the oxidizer are good coolants...
  
  
• Timeline of low-temperature technology
  Timeline of low-temperature technology
  The following is a timeline of low-temperature technology and cryogenic technology .-16th century BCE – 17th century CE :...