针对换热管内污垢在线清洗的难题,提出了管内插偏重式螺旋轮自动防除垢技术.理论分析了螺旋轮获得的自转动力矩,并通过实验研究其自转特性;进一步对管内插偏重式螺旋轮的对流传热特性进行实验研究,对比分析偏重因素对传热强化性能的影响.结果表明:在一正一反交替连接时螺旋轮获得的自转速度最大,更有利于螺旋轮的旋转;传热温差为7℃时,管内插螺旋轮的总传热系数比内插螺旋线、内插扭带时分别提高22.2％和12％;传热温差为15℃时,内插不同偏重式螺旋轮的总传热系数与光管相比分别提高89％和112％,与内插普通螺旋轮的传热系数相比分别提高12％和25％,但相应的沿程阻力损失随之增加.考虑传热和阻力两方面因素,对上述管内插物的综合性能进行比较,结果显示内插偏重式螺旋轮的综合性能最好.%Aiming at the online fouling removal problem in heat transfer tubes,the imbalance spiral-gear inserts are proposed.The self-rotation force moment of such inserts is analyzed theoretically,and the selfrotation performance is examined experimentally.The convective heat transfer characteristics are investigated through experiments in order to evaluate the effect of imbalance on heat transfer enhancement.The result shows that the spiral-gears connected clockwise and counterclockwise alternately have the greatest force moment and can spin more easily.For the heat transfer temperature difference of 7℃,the overall heat transfer coefficient of balanced spiral-gear inserts is 22.2 ％ and 12％ higher than that of spiralwire insert and twisted-tape insert,respectively.For the heat transfer temperature difference of 15℃,the overall heat transfer coefficients of the two kinds of imbalance spiral-gear tubes are 89％ and 112％ greater than that of straight tubes without any inserts,and are 12％ and 25％ higher than that with balanced spiral-gear inserts.The flow resistance is increased correspondingly but still in an appropriate range for engineering applications.From the comprehensive performance on heat transfer rate and resistance,the imbalance spiral-gears give the best result.
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