| 摘要 |
PURPOSE:To obtain a supreme heat exchange ratio by a compact construction by providing a flowpath sectional area adjusting member having a conical surface fitted to the inner surface or the outer surface of a tubular coil and fittable in said tubular coil, and shifting the adjusting member to vary the fitting degree with the tubular coil. CONSTITUTION:A JT heat exchanger Ka is provided at the intermediate of an exhaust pipe 13a with a frustrated conical tapered portion 31, and a tubular coil 15a is disposed in tight contact with the inner surface of said portion 15a. On the other hand, a flowpath sectional area adjusting member 32 is disposed in the tubular coil 15a in the form of fitting in the coil 15a. By this construction, a helium gas exhausted from the end portion 11a of the heat exchanger flows to the lower end portion of an exhaust pipe 13a to cool a JT valve 14, and successively flows between the tapered portion 31 and a cylindrical portion 33. In this process, a liquid He within the tubular coil 15a is precooled. In this case, when an operating cylinder 35 is shifted in the direction of arrow 37, an interval between the portion 31 and the cylindrical portion 33, that is, the flowpath sectional area, can be varied. Consequently, it is possible to adjust the flowpath sectional area in accordance with the gas temperature and constantly use the heat exchanger at the supreme heat exchange efficiency.
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