Liquid hydrogen (LH2 or LH 2 ) is the liquid state of the hydrogen element. Hydrogen is found naturally in the form of the molecule H 2 .
To exist as a liquid, H 2 should be cooled below the hydrogen critical point of 33Ã, K. However, in order for the hydrogen to be in full liquid state without boiling at atmospheric pressure, it needs to be cooled to 20.28 Ã, K (-423.17Ã, Â ° F/-252,87Ã, Â ° C). One common method of obtaining liquid hydrogen involves a jet-like compressor in both appearance and principle. Liquid hydrogen is usually used as a concentrated form of hydrogen storage. As in any gas, storing it as a liquid requires less space than storing it as a gas at normal temperature and pressure. However, the fluid density is very low compared to other common fuels. Once thawed, it can be maintained as a liquid in a pressure-insulated and thermally insulated vessel.
There are two isomers of hydrogen spin; Liquid hydrogen comprises 99.79% parahydrogen and 0.21% orthohydrogen.
Video Liquid hydrogen
Histori
In 1885 Zygmunt Florenty WrÃÆ'³blewski published the critical temperature of hydrogen as 33 K; critical pressure, 13.3 atmospheres; and boiling point, 23 K.
Hydrogen was liquefied by James Dewar in 1898 by using regenerative cooling and his invention, a vacuum tube. The first synthesis of the stable form of the isomer of liquid hydrogen, parahidrogen, was achieved by Paul Harteck and Karl Friedrich Bonhoeffer in 1929.
Maps Liquid hydrogen
Spin isomer of hydrogen
Two nuclei in a dihydrogen molecule can have two different spin states. Parahydrogen, where two nuclear spins are antiparallel, more stable than orthohydrogen, where both are parallel. At room temperature, hydrogen gas is mostly in the form of ortho isomers because of heat energy, but ortho-enriched mixtures only metastasize when liquefied at low temperatures. Slowly undergo an exothermic reaction into the para isomer, with enough energy released as heat causing some boiling liquid. To prevent fluid loss during long-term storage, it is intentionally converted to the isomer of theomer as part of the production process, usually using a catalyst such as iron (III) oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromium (III) oxide , or some nickel compounds.
Usage
Liquid hydrogen is a common liquid rocket fuel for rocketry applications - both NASA and the United States Air Force operate a large number of liquid hydrogen tanks with an individual capacity of up to 3.8 million liters (1 million US gallons). In most rocket engines fueled by liquid hydrogen, it first cools the nozzle and other parts before it is mixed with the oxidizer - usually liquid oxygen (LOX) - and burned to produce water with traces of ozone and hydrogen peroxide. Practically H 2 -O 2 rocket engines run rich fuels so the exhaust contains some unburned hydrogen. This reduces the combustion chamber and erosion nozzle. It also reduces the molecular weight of the exhaust, which can actually enhance specific impulses, even if incomplete combustion.
Liquid hydrogen can be used as fuel for internal combustion engines or fuel cells. Various submarines (type 212 submarines, Type 214 submarines) and hydrogen concept vehicles have been built using this form of hydrogen (see DeepC, BMW H2R). Because of the similarity, builders can sometimes modify and share equipment with systems designed for liquefied natural gas (LNG). However, due to the lower volumetric energy, the volume of hydrogen required for combustion is enormous. Unless direct injection is used, the effects of severe gas displacement also inhibit maximum breathing and increase pumping losses.
Liquid hydrogen is also used to cool neutrons for use in neutron scattering. Since neutrons and hydrogen nuclei have the same mass, the exchange of kinetic energy per interaction is maximum (elastic collision). Finally, superheated liquid hydrogen is used in many experimental bubble spaces.
The first thermonuclear bomb, Ivy Mike, uses deuterium liquid (Hydrogen-2), for nuclear fusion.
Properties
The product of its combustion with oxygen only is water vapor (though if its combustion with oxygen and nitrogen it can form toxic chemicals), which can be cooled with some liquid hydrogen. Since water is not harmful to the environment, the engines that burn it can be considered "zero emissions." Liquid hydrogen also has a specific energy that is much higher than gasoline, natural gas, or diesel.
The density of liquid hydrogen is only 70.99 g/L (at 20 K), the relative density is only 0.07. Although its specific energy is about twice that of other fuels, it provides a very low volumetric energy density, many of which fold lower.
Liquid hydrogen requires cryogenic storage technologies such as special thermal insulated containers and requires special handling which is common to all cryogenic fuels. It's similar to, but more severe than liquid oxygen. Even with thermally insulated containers, it is difficult to maintain such low temperatures, and hydrogen will gradually leak (usually at the rate of 1% per day). It also shares many of the same safety issues as other hydrogen forms, as well as cold enough to melt, or even consolidate atmospheric oxygen, which can be a danger of explosion.
The triple point of hydrogen is 13.81 K 7.042 kPa.
Security
Because of its cold temperature, liquid hydrogen is harmful to cold burns. In addition, the hydrogen element as a biologically inert liquid and the only human health hazard as a vapor is oxygen displacement, which results in shortness of breath. Since it is highly flammable, liquid hydrogen must be kept away from heat or fire unless ignition is intended.
See also
References
Source of the article : Wikipedia
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