| 摘要 |
PROBLEM TO BE SOLVED: To reduce a heat absorbing action of a screen tube of an upstream side, to maintain a temperature of a burnt gas flowing to a rear heat transfer part high and to obtain a vapor of a higher temperature, by winding heat insulators on banks of tubes, covering the insulators with heat insulation covers made of a steel, and suppressing heat exchanging of the tube and a burnt gas tube. SOLUTION: The screen tube 14 is formed by connecting a plurality of heat transfer tubes 7a in a flowing direction A of a combustion gas to form banks 17a to 17e of tubes and arranging the banks at a predetermined interval in predetermined banks. The heat insulating devices are provided at the banks, and a heat absorbing action of the tube 14 is suppressed. The devices are continuously provided along an axial center by providing heat insulating units 21 of an axial central direction of the tubes 7a at a predetermined gap. Each tube 7a is covered with a heat insulator made of a heat insulation filler 22 and a heat insulation band 24. Heat insulation covers 27, 28 of the units 21 of upper and lower sides are formed through a predetermined gap. Thus, transferring of a heat between a fluid flowing through the tube 7a and the gas is suppressed, and a temperature drop of the gas due to passage of the gas through the banks can be prevented.
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