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 self-rotation 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 spiral-wire 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.