Carl von Linde – developer of refrigerators & gas separation technology

Carl von Linde – developer of refrigerators & gas separation technology

Carl von Linde

Biography & contributions

Carl von Linde was a German engineer born on June 11, 1842 – died on November 16, 1934. Linde was best known for his refrigeration and gas separation technologies.

Linde also invented the continuous process of liquefying gases in large quantities. in 1895 he succeeded in liquefying air by first compressing it and then letting it expand rapidly, thereby cooling it. Linde's first refrigeration system used Dimethyl ether as the refrigerant.

In 1873 Carl von Lindee built first practical and portable compressor refrigeration machine. In later years he designed ammonia-compressor driven refrigerator called Kuhlschrank.

In 1878 von Linde started Linde AG (fka: Lindes Eismaschinen AG).

In 1894 linde developed Linde technique for the liquefaction of large quantities of air.

In 1895 carl von Linde produced large amounts of liquid air using the Thomson-Joule effect.

In 1902 he and his staff at Linde AG developed a system that separates liquid oxygen and nitrogen from the liquefied air.

In 1904 he invented oxyacetylene torch, which is used for metal cutting and welding purposes.

Liquefaction of Gases

Liquefaction of gases is the physical conversion of a gas into a liquid state. It is used for analyzing the fundamental properties of gas molecules, for the storage of gases.

A gas may be liquefied by cooling or by the application of high pressure or by the combined effect of both. The first successful attempt for liquefying gases was made by Faraday.

Gases for which the intermolecular forces of attraction are small such as H2, N2, Ar and O2, have low values of Tc and cannot be liquefied by the application of pressure are known as “permanent gases” while the gases for which the intermolecular forces of attraction are large, such as polar molecules NH3, SO2 and H2O have high values of Tc and can be liquefied easily.

Methods of liquefaction of gases

The modern methods of cooling the gas to or below their Tc and hence of liquefaction of gases are done by following methods

  • Linde's method
  • Claude's method
  • Adiabatic demagnetisation method

Linde's method

Linde's method is based upon the Joule-Thomson effect. It states that when a gas is allowed to expand adiabatically from a region of high pressure to a region of extremely low pressure, it is accompanied by cooling.

Claude's method

Claude's method is based upon the principle that when a gas expands adiabatically against an external pressure, it does some external work. Since work is done by the molecules at the cost of their kinetic energy, the temperature of the gas falls causing cooling.

Adiabatic demagnetisation

Adiabatic demagnetisation is the process by which the removal of a magnetic field from certain materials serves to lower their temperature.

Uses of liquefied gases

Liquefied and gases compressed under a high pressure are of great importance in industries.

(i) Liquid ammonia and liquid sulfur dioxide are used as refrigerants.

(ii) Liquid oxygen is provided to hospitals for conversion to gas for patients with breathing problems

(iii) Liquid nitrogen is used in the medical field for cryosurgery, and by inseminators to freeze semen.

(iv) Liquid carbon dioxide finds use in soda fountains.

(v) Liquid chlorine is used for bleaching, disinfectant purposes and manufacturing of carbon tetrachloride, glycol.

(vi) Liquid air is an important source of oxygen in rockets and jet-propelled planes and bombs.

(vii) Compressed oxygen is used for welding purposes.

(viii) Compressed helium is used in airships.

Joule-Thomson effect

When a real gas is allowed to expand adiabatically through a porous plug or a fine hole into a region of low pressure, it is accompanied by cooling.

Cooling takes place because some work is done to overcome the intermolecular forces of attraction. As a result, the internal energy decreases and so does the temperature.

Ideal gases do not show any cooling or heating because there are no intermolecular forces of attraction i.e., they do not show the Joule-Thomson effect.

During Joule-Thomson effect, enthalpy of the system remains constant.

Joule-Thomson coefficient

μ = (∂T/∂P)H

For cooling, μ = +ve

For heating μ = –ve

For no heating or cooling μ = 0

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