Cryogenic Information Library
Hydrogen - Cryogenic Fluids

Liquid Hydrogen (H) typically has to be stored at -423°F (-253°C or 20 K).  The temperature requirements for liquid hydrogen storage necessitate expending a great deal of energy to compress and chill the hydrogen into its liquid state.  The cooling and compressing process requires energy, resulting in a net loss of about 30% of the energy that the liquid hydrogen is storing.  The storage tanks are insulated, to maintain temperature, and reinforced to store the liquid hydrogen under pressure. The margin of safety concerning liquid hydrogen storage is a function of maintaining tank integrity and preserving the temperatures that liquid hydrogen requires.  Combine the cost or energy required for the process to get hydrogen into its liquid state and the cost of tanks required to sustain the storage pressure and temperature, and liquid hydrogen storage becomes very expensive compared to other methods.  Research in the field of liquid hydrogen storage centers around the development of composite tank materials, resulting in lighter, stronger tanks and improved methods for liquefying hydrogen. Scientists had been producing hydrogen for years before it was recognized as an element.  Written records indicate that Robert Boyle produced hydrogen gas as early as 1671 while experimenting with iron and acids.  Henry Cavendish first recognized hydrogen as a distinct element in 1766. Composed of a single proton and a single electron, hydrogen is the simplest and most abundant element in the universe. It is estimated that 90% of the visible universe is composed of hydrogen. Hydrogen is the raw fuel that most stars "burn" to produce energy.  The same process, known as fusion, is being studied as a possible power source for use on earth.  The sun's supply of hydrogen is expected to last another 5 billion years. Hydrogen is a commercially important element.  Large amounts of hydrogen are combined with nitrogen from the air to produce ammonia(NH3) through a process called the Haber process.  Hydrogen is also added to fats and oils, such as peanut oil, through a process called hydrogenation.  Liquid hydrogen is used in the study of superconductors and, when combined with liquid oxygen, makes an excellent rocket fuel. Hydrogen combines with other elements to form numerous compounds.  Some of the common ones are: water (H2O), ammonia (NH3), methane (CH4), table sugar (C12H22O11), hydrogen peroxide (H2O2) and hydrochloric acid (HCl). Hydrogen has three common isotopes.  The simplest isotope, called protium, is just ordinary hydrogen.  The second, a stable isotope called deuterium, was discovered in 1932.  The third isotope, tritium, was discovered in 1934.

Atomic Number 1 Atomic Weight 1.00794 Melting Point 13.81 K Boiling Point 20.28 K Heat of Vaporization 445.6 kj/kg K Specific Heat 9.78 kj/kg K Viscosity 13.06 kg/m-s X 106 Thermal Conductivity 118.5 mW/m-k Dielectric Constant 1.226 Critical Temperature 32.976 K Critical Pressure 1.293 MPa Temperature at Triple Point 13.803 K Pressure at Triple Point 7.042 Mpa X 103 Density .00008988 grams/cc Phase at Room Temperature Gas

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