10th May 1898. Is it Cool Enough?
Hydrogen Gas (H2) was artificially produced in the early 16thc through the mixing of metals with strong acids.(1)
Hydrogen was first liquefied by Sir James Dewar FRS Today in May 1898 using Regenerative Cooling. At the time it was the coldest substance produced.(2)
It was achieved using the Dewar (Vacuum) Flask which unlike the modern ‘thermos’ was to keep liquid cold as the vacuum ensures there are no air molecules through which heat can be transferred.
Dewars are double-walled vessels with a vacuum in the annular space to minimize heat transfer by Conduction and Convection. The walls are silvered to reflect radiant heat.
Dewar produced Solid Hydrogen, the next year, by decreasing the temperature below melting point.
Following the Liquefaction of Hydrogen, Dewar was confident that his concept and design would significantly contribute to storage and transportation, in vacuum vessels, of very cold liquid gases (Cryogenics), of Oxygen, Nitrogen, Air, Helium, Hydrogen and Fluorine.(3)
By 1900 many of the properties of gaseous and liquid Hydrogen were known and Liquid Air, Oxygen and Nitrogen were now to be produced in quantity.
Soon came the advanced suggestion of the use of Liquid Hydrogen as a rocket fuel.
(1) Henry Cavendish FRS (10th October 1731-24th) February 1810, was first to recognise hydrogen gas as a discrete element and that it produced water when burned. He named it hydrogen (water former in Greek) which unusually has no neutron.
(2a) In 1875 Dewar ( 20.9 1842-27.3 1923) was elected to the Jacksonian Professorship of Natural Experimental Philosophy at Cambridge when science was still philosophy.
(2b) In 1895 William Hampson independently developed and patented the Hampson-Linde Cycle to Liquefy Air using the Joule-Thomson expansion process-Regenerative Cooling.
This cooling of Liquid Gases sees the gas is compressed to increase its temperature which is cooled by Heat Exchange. The cool compressed gas is then allowed to decompress.
On each successive cycle the net cooling is more than the heat added at the beginning of the cycle, further cooling it again. The result is a gas or liquid gas colder than it was originally and at the same pressure.