The concept of obtaining low-temperature refrigeration by-use of an expansion engine system in which gaseous helium served as the only circulating refrigerant is no doubt too ancient to be termed novel. However, it is interesting to note that the general philosophy of cryogenic design, on which the present development of helium refrigeration is based, was announced by F. G. Keyes of Massachusetts Institute of Technology about 15 years ago. He pointed out that this form of refrigerator should fulfill a general need in the cryogenics field because it could be applied over the widest range of temperatures obtainable with any refrigerant. The fact that helium is both inert and nontoxic and can be used in such a refrigeration system with only moderate pressures added to his enthusiasm. He expressed the belief that such refrigerators should be used for serving cryostats, as well as for supplying all of the refrigeration required to operate liquefiers. At about the same time, two of Keyes’ associates, S. C. Collins and H. O. McMahon were working on the development of a helium liquefier which eventually lead to the ADL-Collins Helium Cryostat.
KeywordsPressure Ratio Moderate Pressure Refrigeration System Refrigeration Cycle General Philosophy
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