The Impact of Selling the Federal Helium Reserve (2000) / Chapter Skim
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3 Uses of Helium
3 Uses of Helium
Pages 26-39
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From page 26... ...
The remarkable fundamental properties of helium (Box 3.~) make it useful for many applications, but few people appreciate the broad range of crucial roles that it plays in industrial processes, military and civilian aerospace applications, medical technologies, and basic research.
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From page 27... ...
This chapter examines the various current and future uses of helium. The current applications are divided into the main categories used by BEM to track domestic helium usage in 1996 (Figure 3.~: cryogenics, pressurizing and purging, welding, atmospheric control, leak detection, breathing mixtures, lifting, and other uses.
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From page 28... ...
manufacturers have introduced new technologies that dramatically decrease the quantity of liquid helium required. These technologies include improved cryostats with superior thermal efficiency, cryocoolers that recondense the helium, and improved magnet wire and junctions that reduce the size and weight of materials that need to be cooled and lower the small heat load that the magnet itself generates.
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From page 29... ...
In some systems, especially those using radio-frequency or microwave resonators of large size, the uniquely high thermal conductivity of liquid helium also assures that the superconducting system is kept at the uniform temperatures critical to operation. Since there is no alternative material with comparably high thermal-conductivity properties, helium is the only cryogenic fluid that can be reliably used to reach the low temperatures required for all superconducting electromagnets and radio-frequency and microwave resonators currently in use in large-scale systems.
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From page 30... ...
In many instances investigations conducted in strong magnetic fields involve materials that are also cooled using liquid helium. Many investigations at the frontier of materials research require the use of Superconducting Quantum Interference Device (SQUID)
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From page 31... ...
Although this equipment uses helium as a cryogen and, because of inefficiencies and errors, may not eliminate helium loss entirely, a number of commercial suppliers of instrumentation have begun marketing systems equipped with these cryocoolers. For some of the more delicate experimental investigations, the current generation of cryocoolers is mechanically and electronically too noisy, however, and some applications involving very sensitive measurements may require the development of less noisy refiigeration systems.
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From page 32... ...
Other gases would freeze, producing particles that could clog equipment and seize an engine, or react with or dissolve in the liquid hydrogen, reducing engine efficiency, all with potentially disastrous results. The use of liquid and gaseous helium for pressurizing and purging rocket propulsion systems by the aerospace industry and the National Aeronautics and Space Administration (NASA)
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From page 33... ...
The benefits of its use include greater welding penetration in thick joints and in metals with very high thermal conductivity; higher travel speeds, permitting greater productivity; better shielding-gas coverage in vertical and overhead position welds; and flatter surface of root pass when used as a backing gas. Some weld compositions can tolerate a wide variety of shielding gases, but others are quite demanding.
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From page 34... ...
Optical Fiber Manufacture Fiber-optic technology is a burgeoning field that is becoming increasingly important in modern communications. The manufacture of optical fibers critically depends on the use of helium gas.
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From page 35... ...
It is critical in the manufacture of large rocket engines; the manufacture and maintenance of vacuum equipment in all aspects of industrial processing, including the electronics industry and the advanced materials industry; and in scientific research. Indeed, helium leak detection is the standard in any activity requiring leak-tight systems.
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From page 36... ...
Other Uses of Helium Other uses of helium include minor medical uses and uses in lasers not covered in previous sections. The total amount of helium used for these purposes was about 320 million scf (~.9 million scary)
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From page 37... ...
Nevertheless, it is essential to mention it as a potential user of helium as a refiigerant for superconducting magnets, which would probably require liquid-helium temperature refiigeration even if they were made from high-temperature superconducting wire.
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From page 38... ...
. Cryogenic Wind Tunnels Other potentially important uses for helium are in the operation of high-Reynolds-number wind tunnels, which would facilitate testing the behavior of aircraft ant} ships, and highRayleigh-number Benard cells, which could lead to the realistic modeling of convective behavior in weather patterns and other studies of turbulent and convective phenomena having astrophysical and geophysical significance.
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From page 39... ...
can be used in a structure known as a Benard cell to study convection phenomena. 1 ~ This is possible because buoyancy forces dominate viscous forces in low-viscosity helium gas, leading to high Rayleigh numbers and convective behavior.
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