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Gaseous hydrogen is molecular hydrogen and does not cause embrittlement, though it can cause a hot hydrogen attack (see below). It is the atomic hydrogen from a chemical attack which causes embrittlement because the atomic hydrogen dissolves quickly into the metal at room temperature. [6] Gaseous hydrogen is found in pressure vessels and pipelines.
When the metal is stressed, the stress is concentrated near the grain boundaries due to hydrogen atoms, allowing a crack to nucleate and propagate along the grain boundaries to relieve the built-up stress. There are many ways to prevent or reduce the impact of hydrogen embrittlement in metals.
Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [12] The density of liquid hydrogen is only 70.85 kg/m 3 (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.
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 expanding; typically caused by the pressure loss from flow through a valve or porous plug while keeping it insulated so that no heat is exchanged with the environment.
Liquid nitrogen. 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, for example, turboexpanders.
Japan has a liquid hydrogen (LH2) storage facility at a terminal in Kobe, and was expected to receive the first shipment of liquid hydrogen via LH2 carrier in 2020. [162] Hydrogen is liquified by reducing its temperature to −253 °C, similar to liquified natural gas (LNG) which is stored at −162 °C.
The Hindenburg disaster is an example of a large hydrogen explosion. Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704's highest rating of four on the flammability scale because it is flammable when mixed even in small amounts with ...
It should not be confused with the term stress corrosion cracking which is an anodic cracking mechanism. Susceptible alloys, especially steels, react with hydrogen sulfide (H 2 S), forming metal sulfides (MeS) and atomic hydrogen (H •) as corrosion byproducts. Atomic hydrogen either combines to form H 2 at the metal surface or diffuses into ...