2. CRYOGENIC AND ITS DEVELOPMENT Cryogenics The branches of physics and engineering that involve the study of very low temperatures, how to produce them, and how materials behave at those temperatures. The upper limit of cryogenic temperatures has not been agreed on, but the National Institute of Standards and Technology has suggested that the term cryogenics be applied to all temperatures below -150°C (-238°F or 123° above absolute zero on the Kelvin scale). Some scientists regard the normal boiling point of oxygen (-183°C or -297°F), as the upper limit. Cryogenic temperatures are achieved either by the rapid evaporation of volatile liquids or by the expansion of gases confined initially at pressures of 150 to 200 atmospheres. The expansion may be simple, that is, through a valve to a region of lower pressure, or it may occur in the cylinder of a reciprocating engine, with the gas driving the piston of the engine. The second method is more efficient but is also more difficult to apply. Pioneering work in low-temperature physics by the British chemists Sir Humphrey Davy and Michael Faraday, between 1823 and 1845, prepared the way for the development of cryogenics. Davy and Faraday generated gases by heating an appropriate mixture at one end of a sealed tube shaped like an inverted V. The other end was chilled in a salt-ice mixture.. The combination of reduced temperature and increased pressure caused the evolved gas to liquefy. When the tube was opened, the liquid evaporated rapidly and cooled to its normal boiling point. By evaporating solid carbon dioxide mixed with other, at low pressure, Faraday finally succeeded in reaching a temperature of about 163 K (about -110°C/-166°F).If a gas initially at a moderate temperature is expanded through a valve, its temperature increases. But if its initial temperature is below the inversion temperature, the expansion will cause a temperature reduction as the result of what is called the Joule-Thomson effect. The inversion temperatures of hydrogen and helium, two primary cryogenic gases, are extremely low, and to achieve a temperature reduction through expansion, these gases must first be pre-cooled below their inversion temperatures.
2. CRYOGENIC AND ITS DEVELOPMENT Cryogenics The branches of physics and engineering that involve the study of very low temperatures, how to produce them, and how materials behave at those temperatures. The upper limit of cryogenic temperatures has not been agreed on, but the National Institute of Standards and Technology has suggested that the term cryogenics be applied to all temperatures below -150°C (-238°F or 123° above absolute zero on the Kelvin scale). Some scientists regard the normal boiling point of oxygen (-183°C or -297°F), as the upper limit. Cryogenic temperatures are achieved either by the rapid evaporation of volatile liquids or by the expansion of gases confined initially at pressures of 150 to 200 atmospheres. The expansion may be simple, that is, through a valve to a region of lower pressure, or it may occur in the cylinder of a reciprocating engine, with the gas driving the piston of the engine. The second method is more efficient but is also more difficult to apply. Pioneering work in low-temperature physics by the British chemists Sir Humphrey Davy and Michael Faraday, between 1823 and 1845, prepared the way for the development of cryogenics. Davy and Faraday generated gases by heating an appropriate mixture at one end of a sealed tube shaped like an inverted V. The other end was chilled in a salt-ice mixture.. The combination of reduced temperature and increased pressure caused the evolved gas to liquefy. When the tube was opened, the liquid evaporated rapidly and cooled to its normal boiling point. By evaporating solid carbon dioxide mixed with other, at low pressure, Faraday finally succeeded in reaching a temperature of about 163 K (about -110°C/-166°F).If a gas initially at a moderate temperature is expanded through a valve, its temperature increases. But if its initial temperature is below the inversion temperature, the expansion will cause a temperature reduction as the result of what is called the Joule-Thomson effect. The inversion temperatures of hydrogen and helium, two primary cryogenic gases, are extremely low, and to achieve a temperature reduction through expansion, these gases must first be pre-cooled below their inversion temperatures.
52650290-LIQUID-NITROGEN-AS-A-NON-POLLUTING-FUEL-DOC.docx