Liquefaction of gases is physical conversion of a gas into a liquid state (condensation). The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example, turboexpanders.
Fuel gas is one of a number of fuels that under ordinary conditions are gaseous. Most fuel gases are composed of hydrocarbons (such as methane and propane), hydrogen, carbon monoxide, or mixtures thereof. Such gases are sources of energy that can be readily transmitted and distributed through pipes.
Fuel gas is contrasted with liquid fuels and solid fuels, although some fuel gases are liquefied for storage or transport (for example, autogas and liquified petroleum gas). While their gaseous nature has advantages, avoiding the difficulty of transporting solid fuel and the dangers of spillage inherent in liquid fuels, it also has limitations. It is possible for a fuel gas to be undetected and cause a gas explosion. For this reason, odorizers are added to most fuel gases. The most common type of fuel gas in current use is natural gas.
Heike Kamerlingh Onnes (Dutch: [ˈɦɛikə ˈkaːmərlɪŋ ˈɔnəs]; 21 September 1853 – 21 February 1926) was a Dutch experimental physicist who became the first to liquefy helium, cooling it to near 1.5 kelvin (K). For this work, he was awarded the Nobel Prize in Physics in 1913.
In 1911, using liquid helium to investigate the electrical conductivity of solid mercury, Kamerlingh Onnes found that its electrical resistance vanishes at 4.2 K, i.e. superconductivity.