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The Hampson–Linde cycle is a process for the
The cooling cycle proceeds in several steps:
# The gas is compressed, which adds external energy into the gas, to give it what is needed for running through the cycle. Linde's US patent gives an example with the low side pressure of and high side pressure of .
# The high pressure gas is then cooled by immersing the gas in a cooler environment; the gas loses some of its energy (heat). Linde's patent example gives an example of brine at 10°C.
# The high pressure gas is further cooled with a countercurrent heat exchanger; the cooler gas leaving the last stage cools the gas going to the last stage.
# The gas is further cooled by passing the gas through a Joule–Thomson orifice (expansion valve); the gas is now at the lower pressure.
#: The low pressure gas is now at its coolest in the current cycle.
#: Some of the gas condenses and becomes output product.
# The low pressure gas is directed back to the countercurrent heat exchanger to cool the warmer, incoming, high-pressure gas.
# After leaving the countercurrent heat exchanger, the gas is warmer than it was at its coldest, but cooler than it started out at step 1.
# The gas is sent back to the compressor, mixed with warm incoming makeup gas (to replace condensed product), and returned to the compressor to make another trip through the cycle (and become still colder).
In each cycle the net cooling is more than the heat added at the beginning of the cycle. As the gas passes more cycles and becomes cooler, reaching lower temperatures at the expansion valve becomes more difficult.
liquefaction of gases
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 ...
, especially for air separation
An air separation plant separates atmospheric air into its primary components, typically nitrogen and oxygen, and sometimes also argon and other rare inert gases.
The most common method for air separation is fractional distillation. Cryogenic air ...
. William Hampson
William Hampson (18541926) was the first person to patent a process for liquifying air.
Early life
William Hampson was born on 14 March 1854, the second son of William Hampson of Puddington, Cheshire, England.Who Was Who, Published by A&C B ...
and Carl von Linde
Carl Paul Gottfried von Linde (11 June 1842 – 16 November 1934) was a German scientist, engineer, and businessman. He discovered a refrigeration cycle and invented the first industrial-scale air separation and gas liquefaction processes, whi ...
independently filed for patents of the cycle in 1895: Hampson on 23 May 1895 and Linde on 5 June 1895.
The Hampson–Linde cycle introduced regenerative cooling
Regenerative cooling is a method of cooling gases in which compressed gas is cooled by allowing it to expand and thereby take heat from the surroundings. The cooled expanded gas then passes through a heat exchanger where it cools the incoming comp ...
, a positive-feedback cooling system. The heat exchanger
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
arrangement permits an absolute temperature difference (e.g. J–T cooling for air) to go beyond a single stage of cooling and can reach the low temperatures required to liquefy "fixed" gases.
The Hampson–Linde cycle differs from the Siemens cycle
The Siemens cycle is a technique used to cool or liquefy gases. A gas is compressed, leading to an increase in its temperature due to the directly proportional relationship between temperature and pressure (as stated by Gay-Lussac's law). The c ...
only in the expansion step. Whereas the Siemens cycle has the gas do external work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an animal tr ...
to reduce its temperature, the Hampson–Linde cycle relies solely on the Joule–Thomson effect
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 valv ...
; this has the advantage that the cold side of the cooling apparatus needs no moving parts.
The cycle
The cooling cycle proceeds in several steps:
# The gas is compressed, which adds external energy into the gas, to give it what is needed for running through the cycle. Linde's US patent gives an example with the low side pressure of and high side pressure of .
# The high pressure gas is then cooled by immersing the gas in a cooler environment; the gas loses some of its energy (heat). Linde's patent example gives an example of brine at 10°C.
# The high pressure gas is further cooled with a countercurrent heat exchanger; the cooler gas leaving the last stage cools the gas going to the last stage.
# The gas is further cooled by passing the gas through a Joule–Thomson orifice (expansion valve); the gas is now at the lower pressure.
#: The low pressure gas is now at its coolest in the current cycle.
#: Some of the gas condenses and becomes output product.
# The low pressure gas is directed back to the countercurrent heat exchanger to cool the warmer, incoming, high-pressure gas.
# After leaving the countercurrent heat exchanger, the gas is warmer than it was at its coldest, but cooler than it started out at step 1.
# The gas is sent back to the compressor, mixed with warm incoming makeup gas (to replace condensed product), and returned to the compressor to make another trip through the cycle (and become still colder).
In each cycle the net cooling is more than the heat added at the beginning of the cycle. As the gas passes more cycles and becomes cooler, reaching lower temperatures at the expansion valve becomes more difficult.
References
Further reading
* * * Thermodynamic cycles Cryogenics Industrial gases 1895 in science 1895 in Germany {{thermodynamics-stub