To enhance the efficiency of a motor and improve its service life by expanding a tube by a mixed pressure fluid fed from a mixed fluid feeding means to feed the mixed pressure fluid mixed with a lubricant, and pushing to turn a roller by expansion of the tube to rotate a rotor.

When hot water is fed to an evaporator, evaporated liquid such as liquid pentane in the evaporator is evaporated to become pentane gas PG, and this pentane gas PG is mixed with lubricating oil separately fed by an oil pump and fed in the mixed state to a feed port 3 of a tube motor through a gas pipe 28. This pentane gas PG is fed to a first chamber (a) of a tube 4, but since the first chamber (a) is in a sealed state by a roller 7 energized by a pre-load spring 12, the first chamber (a) is expanded by the feeding of the pentane gas so as to push a roller 7 to turn in a forward direction R along with other rollers 8-10 by the expansion force. A rotor 16 is therefore rotated clockwise.