This paper introduces several liquefaction and refrigeration cycles, such as Linde cycle, Claude cycle, Reverse Stirling cycle and Gifford-MacMahon cycle with the examples of helium machine in foreign countries, and discusses about their characteristics. At present helium machine is in a stage of completion as the industrial and chemical machinery, but from the standpoint of electrical machinery, it is still in a very infant stage. It is necessary to improve its reliability and to solve its maintenance free problems like housefold refrigerators.
In this paper are described basic principles of refrigeration, followed by various refrigeration cycles, classical and modern, with special emphasis on their meanings but without recourse to complicated formulae.
The recent development of large scale refrigerator and liquefier at low temperatures is described. Several typical plants which have already been installed are explained such as a large scale helium liquefiers in helium extraction plants, a tonnage hydrogen liquefier for the Saturn rocket fuel production, and combined refrigeration system of helium and hydrogen for a bubble chamber with a superconducting magnet.
This paper presents a review of the art of small cryogenic refrigerator and considers problems for future demand. In this paper, I would limit my discussion to only five cycles; Stirling, Gifford-McMahon, Solvay, Vuilleumier and Taconis. Because the majority of successful small refrigerators use thermal regenerators, and these cycles are the typical cycles using thermal regenerators. Among many cryogenic applications, the Parametric amplifier for telecommunications is already in industrial use. Now, Infrared detector and superconducting applications are in progress and look promising. When we think about future demand for small cryogenic refrigerators, high reliability and low cost of refrigeration will be the decisive factors.
The improvement of reliability of the cryogenic system is now an indispensable requisite. it is no exaggeration to say that the cryogenic refrigerator is especially lagging behind the superconductivity devices in reliability. This report describes what ideas are necessary to achieve a reliable cryogenic system design. These ideas were applied to the development of a small-sized helium refrigerator, particularly of its expansion engine. As a result, we have succeeded in developing an automatic valve expansion engine, which provides a mean time between failures (MTBF) of 5, 000hrs at 70% confidence level.
In the rapidly growing superconducting engineering including superconducting levitation magnets for superhigh speed trains, cooling problem is one of the most important subject. This also applys to the development of cryogenic transmission cables. However, up to the present time no systematic discussion both from engineering and economic stand-point have been made in this field. This article describes cooling system problems in conncetion with the widely located superconducting magnet systems in the field of high energy physics and with the forthcoming cryogenic cable systems.
Problems concerning cooling of long-distance cryogenic system are disussed, with special regard to the application for low-temperature power transmission. Inportance of transient state, such as first stage cooling down, or power transmissiom fault, is stressed, because it is probable that some main dimensions of cryogenic systems will be determined solely from the considerations of these transient states, in advance of the optimization of whole electrical and cryogenic system.
Recent advances in the field of heat transfer or cooling with supercritical helium are reviewed: The region boundaries are discussed and the physical properties of supercritical helium are described. A conventional heat transfer correiation may be used to predict the heat flux. Force-cooled superconducting systems are compared with traditional pool system. Advantages of these systems will be particularly for large coil and long cable. But the design and construction of such systems are associated with some problems to be solved.
In the United States of America the natural gas which contains about 0.4% up helium content is used as main material for producing the helium gas. The equipment recently developed in France separates and rectifies 0.05% of helium gas to produce high purity of helium gas. This will serve as a good reference to how to go on with developing the helium resources in Japan. The long and continuous operation of helium liquefier and refrigerator depends upon settling a problem that the impurities in helium gas is accumulated in the heat exchanger, as well as the good performance of compressor and turbine. We explain the present condition regarding the adsorbing method mainly adopted for purifying the helium gas. We have described so far the measuring principle and accuracy of the various analizers, like those for trace oxygen, nitrogen, moisture, methane and carbon doixide gas, as those closely related to the impurities in helium gas. Further we have discussed the comparison of various methods in case of purging the air in the air-tight vessels by using the helium gas, and the course of impurities entraining into the helium equipment having been examined.