PURPOSE: To make it easier to select the material for use and design the cooling structure so as to reduce the cost by providing the support shaft of a rotary body on the low-temperature side under it and by supporting the thrust load and radial load.

CONSTITUTION: A rotary body 3 has its support shaft 4 under the axis of the rotary shaft and at the lower end of the support shaft 4 a support bearing 6 which can support the thrust load and radial load. The support shaft 4 has at an upper position a guide bearing 5 which can support the radial load. High- temperature fluid 8 is made to flow from above the rotor 3 downward and cold-temperature fluid 7, from under the rotor upward. Supported by a guide bearing 5, the rotary body 3 stably revolves around the support shaft 4 while the heat exchange takes place between the high-temperature fluid 8 and the low-temperature fluid 7. The temperature rises in the upper part of the rotary body 3 but, since the temperature in the lower part is lowered, use can be made of inexpensive materials, such as carbon steel, for the lower part and moreover the cooling can be effected easily so that a cut in cost can be achieved.