三维翅片管外螺旋流动传热强化

流体在螺旋隔板换热器的壳程类似于塞状流流动，几乎没有返混和流动死区.在相同压降下，其传热系数比普通的弓形隔板换热器高得多.以润滑油作为实验介质，研究了润滑油在螺旋隔板单管换热器的壳程传热和压降性能，并与光滑管进行了性能对比.采用Wilson图解法分别分离出了螺旋隔板花瓣管和光滑管单管换热器的管程传热系数，并计算出各自的壳程传热系数，壳程传热系数相对误差为±3％.实验结果表明，在相同Reynolds数下，螺旋隔板花瓣管单管换热器的Nusselt数和压降Δp分别是螺旋隔板光滑管单管换热器的2～2.7倍和1.3～1.4倍.与螺旋隔板光滑管单管换热器相比，螺旋隔板花瓣管单管换热器的传热性能的提高远高于压降的提高，证明在螺旋流条件下，花瓣管具有很好的传热强化性能.

Heat transfer enhancement for helical flowing outside three-dimensional fin tube

The flow pattern on the shell side of a helically baffled heat exchanger is near plug flow conditions,which almost eliminates backmixing and dead space on the shell side.The heat transfer coefficient of the helically baffled heat exchanger is much higher than that of conventional segmental baffle heat exchanger at the same pressure drop.In this paper, experiments were conducted for cooling water flowing in the tube side on the helically baffled heat exchanger with lubricating oil as the working medium flowing on the shell side.The tested tubes included one petal-shaped finned tube and one smooth tube selected for performance comparison.The heat transfer coefficients were obtained by using the Wilson plot method and pressure drop on the shell side was directly measured for the two heat exchangers.The relative error of heat transfer coefficient on the shell side was within ±3％.The results showed that the Nusselt numbers and pressure drops on the shell side of the helically baffled heat exchanger with petal-shaped finned tube were 2—2.7 and 1.3—1.4 times larger than those of the helically baffled heat exchanger with smooth tube at constant Reynolds number, respectively.The petal-shaped finned tube could significantly improve the shell side heat transfer performance for the helically baffled heat exchanger.