Patent ID: 7424802

Claim:
A steam engine comprising: a fluid container in which working fluid is filled and the working fluid can move; a heating device for heating the working fluid in the fluid container and vaporizing the working fluid to produce steam; a cooling device for cooling down and liquefying the steam vaporized by the heating device; and an output device having a moving member reciprocating by pressure change of the working fluid in the fluid container, and outputting energy converted from the reciprocal movement of the moving member, wherein the fluid container comprises a pipe shaped portion having a heating portion at which the heating device is provided, and a cooling portion at which the cooling device is provided, wherein an inner radius “r 1 ” of the cooling portion is made to almost equal to a depth “δ 1 ” of thermal penetration (at a low pressure), which is calculated by the following formula (1); δ 1 = 2 ⁢ a 1 ω ( 1 ) “a 1 ” is a heat diffusivity of the working fluid at its low pressure, and “ω” is an angular frequency of the movement of the working fluid in the fluid container, and wherein the heat diffusivity “a 1 ” is selected from those values corresponding to a pressure variable range of the working fluid, which is a range of the fluid pressure from the lower limit to a fluid pressure higher than the lower limit by 25%.