Views:11 Author:Site Editor Publish Time: 2019-04-25 Origin:Site
(1) Low temperature engineering application of helium gas
It is well known that the liquid temperature range of xenon is 2 x 10-3 - 5.20 K, the liquid temperature range of hydrogen is 14.2 - 33.0 K, and the liquid temperature range of helium is 24.5 - 44.40 K.
Because helium is chemically inert and has a large latent heat of vaporization (the liquid helium refrigeration energy is 2.7 times that of liquid hydrogen based on the same volume of liquid), helium is often used as a safe coolant for experiments within 25-40K. When the vapor is extracted from the upper part of the liquid helium, it is easy to turn the liquid into a solid helium because the triple point temperature of helium is only about 2.5K lower than its standard boiling point. When the helium is used as a refrigerant, the latent heat of fusion of the solid helium is utilized. It can increase the effective cooling capacity of alfalfa by 20%.
In order to be able to quickly evacuate a large space into a vacuum, a liquid helium cryopump is often used. If the vacuum requirement is not high, a liquid helium cryopump can also be used. A closed-loop micro-refrigerator made of enamel can be used as an infrared detector for missiles. Liquid helium is often used in bubble chambers for high energy particle detection and research.
In the United States, helium is mainly used in bubble chambers, and the demand for one-time is large. In addition, liquid helium is also used in the study of free radicals. With the continuous development of science and technology, liquid helium will be paid more and more attention as a low temperature coolant of 25-40K.
In addition, since thermal noise in many electronic devices is reduced at low temperatures, many radio, infrared, and other radiation detecting instruments can use helium circulation cooling to increase their sensitivity.
(2) Electric light source and detection gas for helium use
Iridium gas is used in almost all modern light sources, and helium is mainly used to fill various fluorescent lamps, illuminating signal devices, and glow lamps.
For the low-pressure discharge tube, in the clean glass tube, pure bismuth produces orange light, and argon and argon are mixed in different proportions and filled into various filter glass tubes to make a colorful neon (word display light).
Xenon low-voltage discharge tubes are widely used as indicator lights. Due to the strong transmission of red light from the neon light, it has not been used for a long time to fill various signal devices, and it is used as a display mark for water, land and transportation sites such as ports, airports and stations.
Helium is used in the radioactive ionization detector, and a mixture of helium, argon and helium is used in the Geiger-Muller counter. In addition, helium gas can also be filled in some high-pressure tube transfer switches and adjustment tubes.
In the tracer particle detector, helium is a commonly used fill gas for the spark chamber and the electron flow chamber. Liquid helium is also widely used in low temperature radiation detectors and other specialized instruments used in space exploration programs. Helium is mixed with argon, helium and mercury vapor to fill the phosphor tube. Helium and argon can be used to fill a thyratron radio tube.
Laser technology is widely used in steroid gas, and Ne-He continuous laser is widely used in optical applications with a power of only a few watts.
(3) Deep sea diving breathing gas for helium use
In addition to helium, helium can also be used to prepare breathing mixtures for deep water operations.
Usually, when the diver is working in a deep water and high pressure environment, if ordinary compressed air is used for oxygen supply, not only the breathing resistance is high, but also the nitrogen in the compressed air is partially dissolved in the blood. When the water depth is below 40 m, significant anesthetic effect is produced. At about 80m, the physiological function is basically lost and the body is depleted.
Because light sputum gases (such as Ne, He) have little or no anesthetic ability to the human body, they can be used instead of nitrogen to prepare divers for deep sea operation breathing mixtures. Due to the lower density and viscosity, the helium-oxygen or helium-oxygen breathing mixture makes the pressure easy to release and the respiratory resistance is reduced, which can effectively reduce the diver's physical energy consumption. For the helium-oxygen breathing mixture, the sound frequency changes greatly due to the high speed of sound, and there is a problem of deep water communication.
Moreover, the high rate of sputum transmission increases the rate of heat loss in humans, so that effective wetsuits and respiratory preheaters must often be used. In this respect, the helium-oxygen breath mixture is better than the helium-oxygen breath gas because it has the advantages of small sound distortion and poor heat transfer. The helium-oxygen breathing mixture is suitable for 100-300m deep water operation. Above 300m, the density of helium is increased, and helium-oxygen breathing mixture must be used.
Helium-oxygen breathing gas has been successfully used in deep-sea diving operations. Regardless of the shallow water depth, helium-oxygen breathing mixture is commonly used. In order to overcome their respective shortcomings and deficiencies, the possibility of preparing deep-sea diving breathing gas in different proportions using strontium, barium and oxygen is being studied.