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• 化工学报 • Previous Articles Next Articles
Chen Tingkuan and Jia Xiuzhuang (Xian Jiaotong University, Xian)According to the authors investigation on boiling heat transfer in vertical U-shaped tubes, the boiling heat transfer deterioration on the inner side of the bend occurring at lower mass velocities and lower steam qualities leads to elevated wall temperature on the inner side of the bend due to the stratification of the steam-water flow under the action of both centrifugal and gravitational forces. In order to improve the boiling heat transfer performance, modified U-shaped tubes with inclined upward bottom were tested in a high pressure electrically heated water loop under the conditions of p = 75- 14MPa, G = 500-1400kg/(m2·s) and q = 90-330kW/m2. This paper describes the experimental results on the boiling heat transfer deterioration in the bend of modified U-shaped tubes with R1/d=3, R2/d = 6 and R1/d=6, R2/d=6, and bottom straight tube inclination of 18? According to the tests the mass velocity at which the wall temperature begins to rise is much decreased than that in ordinary U-shaped tube. So the modified U-shaped tubes may be recommended tor waste heat boilers in synthetic ammonia plants for ensuring safe operation.
陈听宽,贾岫庄