| 摘要 |
<p>PURPOSE:To prevent heat medium from deteriorating due to overheat and the life of a heat medium heater from decreasing by filling the liquid which is hot deteriorated at the surface temperature of a heating tube in a space between the outer surface of the tube and the inner surface of an outer tube, and so setting the surface area of the outer tube that the surface temperature of the outer tube becomes the deteriorating temperature or lower of the medium. CONSTITUTION:An outer tube 22 is enclosed in a sealing state around the heating section of a heating tube 21 which contains an electric heater 20 ignited by night power or the like. A liquid injection plug 24 and an air vent plug 25 are provided suitably at the tube 22, and liquid which is not deteriorated at the temperature of the outer surface of the tube 21 is filled in an inner space. As the liquid, water can be used. The water is evaporated by the heating temperature to become stream of a predetermined pressure, the heat of the tube is transferred to the outer tube through the steam, and transferred, in turn from the outer tube to thermal medium disposed outside. If a heat source is of an electric heater, the heat transfer amount is constant. Accordingly, if the surface area of the outer tube is suitably increased, the difference of the surface temperature of the outer tube to the temperature of the medium is reduced, and can be decreased to the deteriorating temperature or lower of the medium.</p> |
