Liquid hydrogen
| |||
Names | |||
---|---|---|---|
IUPAC name
Hydrogen
| |||
Systematic IUPAC name
Liquid hydrogen | |||
Other names
Hydrogen (cryogenic liquid), Refrigerated hydrogen; LH2, para-hydrogen
| |||
Identifiers | |||
3D model (
JSmol ) |
|||
ChEBI | |||
ChemSpider | |||
KEGG | |||
PubChem CID
|
|||
RTECS number
|
| ||
UNII | |||
UN number | 1966
| ||
| |||
| |||
Properties | |||
H2(l) | |||
Molar mass | 2.016 g·mol−1 | ||
Appearance | Colorless liquid | ||
Density | 0.07085 g/cm3 (4.423 lb/cu ft)[1] | ||
Melting point | −259.14 °C (−434.45 °F; 14.01 K)[2] | ||
Boiling point | −252.87 °C (−423.17 °F; 20.28 K)[2] | ||
Hazards | |||
GHS labelling:[3] | |||
Danger | |||
H220, H280 | |||
P210, P377, P381, P403 | |||
NFPA 704 (fire diamond) | |||
571 °C (1,060 °F; 844 K)[2] | |||
Explosive limits
|
LEL 4.0%; UEL 74.2% (in air)[2] | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Liquid hydrogen (H2(l)) is the
To exist as a liquid, H2 must be cooled below its
There are two spin isomers of hydrogen; whereas room temperature hydrogen is mostly orthohydrogen, liquid hydrogen consists of 99.79% parahydrogen and 0.21% orthohydrogen.[5]
Hydrogen requires a theoretical minimum of 3.3 kWh/kg (12 MJ/kg) to liquefy, and 3.9 kWh/kg (14 MJ/kg) including converting the hydrogen to the para isomer, but practically generally takes 10–13 kWh/kg (36–47 MJ/kg) compared to a 33 kWh/kg (119 MJ/kg) heating value of hydrogen.[7]
History
In 1885, Zygmunt Florenty Wróblewski published hydrogen's critical temperature as 33 K (−240.2 °C; −400.3 °F); critical pressure, 13.3 standard atmospheres (195 psi); and boiling point, 23 K (−250.2 °C; −418.3 °F).
Spin isomers of hydrogen
The two nuclei in a dihydrogen molecule can have two different spin states. Parahydrogen, in which the two
Uses
Liquid hydrogen is a common liquid rocket fuel for rocketry application and is used by NASA and the U.S. Air Force, which operate a large number of liquid hydrogen tanks with an individual capacity up to 3.8 million liters (1 million U.S. gallons).[9]
In most
Liquid hydrogen can be used as the fuel for an
Liquid hydrogen is also used to cool neutrons to be used in neutron scattering. Since neutrons and hydrogen nuclei have similar masses, kinetic energy exchange per interaction is maximum (elastic collision). Finally, superheated liquid hydrogen was used in many bubble chamber experiments.
The first thermonuclear bomb, Ivy Mike, used liquid deuterium, also known as hydrogen-2, for nuclear fusion.
Properties
The product of hydrogen combustion in a pure oxygen environment is solely water vapor. However, the high combustion temperatures and present atmospheric nitrogen can result in the breaking of N≡N bonds, forming toxic NOx if no exhaust scrubbing is done.
The density of liquid hydrogen is only 70.85 kg/m3 (at 20 K), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density, many fold lower.
Liquid hydrogen requires
The triple point of hydrogen is at 13.81 K[5] 7.042 kPa.[13]
Safety
Due to its cold temperatures, liquid hydrogen is a hazard for cold burns. Hydrogen itself is biologically inert and its only human health hazard as a vapor is displacement of oxygen, resulting in asphyxiation, and its very high flammability and ability to detonate when mixed with air. Because of its flammability, liquid hydrogen should be kept away from heat or flame unless ignition is intended. Unlike ambient-temperature gaseous hydrogen, which is lighter than air, hydrogen recently vaporized from liquid is so cold that it is heavier than air and can form flammable heavier-than-air air–hydrogen mixtures.
See also
- Industrial gas
- Liquefaction of gases
- Hydrogen safety
- Compressed hydrogen
- Cryo-adsorption
- Expansion ratio
- Gasoline gallon equivalent
- Slush hydrogen
- Solid hydrogen
- Metallic hydrogen
- Hydrogen infrastructure
- Hydrogen-powered aircraft
- Liquid hydrogen tank car
- Liquid hydrogen tanktainer
- Hydrogen tanker
References
- ^ Thermophysical Properties of Hydrogen, nist.gov, accessed 2012-09-14
- ^ a b c d Information specific to liquid hydrogen Archived 2009-07-17 at the Wayback Machine, harvard.edu, accessed 2009-06-12
- ^ GHS: GESTIS 007010
- ^ "We've Got (Rocket) Chemistry, Part 1". NASA Blog. 15 April 2016. Retrieved 3 October 2021.
- ^ a b c IPTS-1968, iupac.org, accessed 2020-01-01
- ^ "Liquid Hydrogen Delivery". Energy.gov. Retrieved 2022-07-30.
- ^ Gardiner, Monterey (2009-10-26). DOE Hydrogen and Fuel Cells Program Record: Energy requirements for hydrogen gas compression and liquefaction as related to vehicle storage needs (PDF) (Report). United States Department of Energy.
- ^ a b "Liquefaction of "Permanent" Gases" (PDF of lecture notes). 2011. Retrieved 2017-10-16.
- ISBN 978-0-203-02699-1.
- S2CID 236732702.
- .
- ^ a b Hydrogen As an Alternative Fuel Archived 2008-08-08 at the Wayback Machine. Almc.army.mil. Retrieved on 2011-08-28.
- ISBN 0-07-297675-6