| 摘要 |
PURPOSE:To reduce the deterioration in heat transfer performance while maintaining sufficient corrosion restraining effect by a method wherein a silicon resin coating film is formed on the inner surface of an U-tube made of copper or copper alloy so as to have a specified thickness. CONSTITUTION:Silicon resin coating film having the thickness of 5 to 20mum is formed on the inner surface of an U-tube made of copper or copper alloy. When the thickness of the coating film is less than 5mum, it is hard to form uniform coating film and, therefore, sufficient anti-corrosion property nd durability can not be obtained. When the thickness of the coating film exceeds 20mum, heat transfer performance is spoiled remarkably. According to the results of the evaluation of the coefficient of overall heat transmission, the test of durability against jet stream and the evaluation of the adhering property of the coating film, which are effected on the straight part and the worked part of U-shape bending of said heat transfer tube coated with the inner coating film after working U-shape bending with radius of 40mm and effecting stress removing annealing for 80 minutes at 400 deg.C, remarkable industrial effects, such as maintaining of sufficient corrosion restraining effect, slight deterioration of heat transfer performance and the like, may be obtained. |
