| 摘要 |
PURPOSE:To miniaturize the size of a steam generator, by laying out an inner tube and outer tube made of iron-based alloy steel so that their cross sections may become a concentric circle, and allowing a porous member having excellent heat conductivity and porosity exceeding a specified % to exist between said inner pipe and outer pipe. CONSTITUTION:A double tube type heat transfer tube 102 has a porous member 111, which is provided with excellent heat conductivity, existing between an inner tube 103 and an outer tube 104, and their porosity is specified to 3% or more. The inner tube 103 and the outer tube 104 comprise high chrome steel, for example. The leakage caused by a crack produced on the surfaces of the inner tube 103 or the outer tube 104 is spread through the pores within the porous member 111, which is excellent in heat conductivity, and is transmitted promptly in the axial direction of the tube, which makes it possible to detect the generation of damage earlier than the conventional mechanism. Therefore, this construction can satisfy both damage detection performance and heat transfer performance, which are under antinomic relation each other in the prior art embodiment. If the porosity fails to exceed 3%, gas permeability will be insufficient and difficult to detect the generation of leakage. |
