ASHRAE REFRIGERATION SI CH 47

Abstract

<strong>GENERAL APPLICATIONS</strong> <br>The application of cryogenic engineering has become extensive. In the United States, for example, nearly 30% of the oxygen produced by cryogenic separation is used by the steel industry to reduce the cost of high-grade steel, and another 20% is used in the chemical process industry to produce a variety of oxygenated compounds. Liquid hydrogen production has risen from laboratory quantities to over 2.1 kg/s. Similarly, liquid helium demand has required the construction of large plants to separate helium from natural gas cryogenically. Energy demand likewise has accelerated construction of large base-load liquefied natural gas (LNG) plants. Applications include high-field magnets and sophisticated electronic devices that use the superconductivity of materials at low temperatures. Space simulation requires cryopumping (freezing residual gases in a chamber on a cold surface) to provide the ultrahigh vacuum representative of conditions in space. This concept has also been used in commercial high-vacuum pumps. <br>The food industry uses large amounts of liquid nitrogen to freeze expensive foods such as shrimp and to maintain frozen food during transport. Liquid-nitrogen-cooled containers are used to preserve whole blood, bone marrow, and animal semen for extended periods. Cryogenic surgery is performed to treat disorders such as Parkinson's disease. Medical diagnosis uses magnetic resonance imaging (MRI), which requires cryogenically cooled superconducting magnets. Superconducting magnets are now an essential component in high-energy accelerators and target chambers. Finally, the chemical processing industry relies on cryogenic temperatures to recover valuable heavy components or upgrade the heat content of fuel gas from natural gas, recover useful components such as argon and neon from air, purify various process and waste streams, and produce ethylene from a mixture of olefin compounds.