Abstract:

In order to reduce the flow resistance of shell sides of double-pipe heat exchangers enhanced by the winglet-type vortex generators and helical fins, a new kind of vortex generators, named streamlined vortex generator was proposed. Heat transfer characteristics and pressure drop behavior of the shell sides enhanced by the streamlined vortex generators and helical fins were investigated by experimental and numerical method. The comparisons on the performance between the streamlined vortex generators and the delta-winglet-pair(DWP)vortex generators were made. The enhancement effects of two installation modes for the streamlined vortex generators, common-flow-down (CFD) and common-flow-up (CFU) of streamlined vortex generators were observed. The drag reduction mechanisms of streamlined vortex generators were analyzed. The results showed that, compared with the delta winglet pair vortex generators, the same(Re < 8000)or slightly lower (Re > 8000)heat transfer coefficients can be achieved by using streamlined vortex generators. However, the drags can be reduced by 21% when the heat transfer areas and the angle of attacks were the same. Under the identical pressure drop condition, the comprehensive performance of the common-flow-up mode was a little better than that of the common-flow-down mode. The drag reduction mechanisms of streamlined vortex generators lay in the improvement of the velocity field and the pressure field.

Key words: heat exchanger, hydrodynamics, computational fluid dynamics, streamline, longitudinal vortex generators, double-pipe heat exchanger

摘要：

为降低翅翼型纵向涡发生器与螺旋片复合强化的套管式换热器壳侧传热阻力，提出一种新型翅翼型纵向涡发生器，即流线型涡发生器。采用实验和数值模拟方法研究了流线型涡发生器与螺旋片复合强化的换热器壳侧的传热和阻力特性并与三角翼型涡发生器（DWP）的强化效果进行比较，考察了流线型涡发生器common-flow-down（CFD）和common-flow-up（CFU）两种安装方式的强化效果，分析了流线型涡发生器的减阻机理。结果表明，在涡发生器面积和迎流角相同的情况下，流线型涡发生器可以取得与三角翼型涡发生器相同（Re<8000）或略低（Re>8000）的传热系数，但其产生的流动阻力比三角翼型涡发生器低21%；在相同压降条件下，common-flow-up安装方式的综合传热效果优于common-flow-down；流线型涡发生器减阻机理在于提高了速度场与压力场的协同性。

关键词: 传热, 流体动力学, 计算流体力学, 流线型, 纵向涡发生器, 套管式换热器