| 摘要 |
PURPOSE:To permit a heat transfer tube to keep the surface temperature thereof higher than the dew point of sulphuric acid and endure the use for a long period of time, by a method wherein a Teflon tube is provided between an inner tube, made of copper or a copper alloy, and an outer tube, made of stainless steel, to form a triplicated tube. CONSTITUTION:A non-metallic tubular body or a porous and low heat conductive tubular body, such as Teflon, glass fiber, asbestos or the like, may be used as the intermediate tubular body having heat insulating properties, however, a Teflon tube is the best from the view points of forming proper ty, workability and economical property. An outer tube 3 of stainless steel is used so as to be suitable for a high temperature such as the temperature of discharge gas of 300 deg.C or more. In this case, the heat trans-. fer area of the tube is increased by finning and it is effective. An inner tube is preferable to be made of copper op a copper alloy, prominent in anticorrosive property and heat conductivity. The inner tube of copper or copper alloy, the intermediate heat insulating tubular body of Teflon and the outer tube of stainless steel are integrated into one body so as to be contacted closely in a degree capable of being slid by thermal expansions.
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