扭曲管换热器壳程传热与压降性能的数值模拟

Numerical simulation of shell side heat transfer and pressure drop characteristics of twisted tube heat exchanger

对扭曲椭圆管换热器壳程的流体流动和热量传递性能运用了可实现的k-ε模型进行了数值模拟,分析了不同的扭距对壳程传热性能的影响。结果显示努赛尔数和摩擦系数随着扭距的减小而增大。同时也分析了扭距对壳程总体传热性能的影响,结果表明壳程整体传热性能开始的时候随着扭距的增大而增大,随后随着扭距的增大而减小。并发现与相邻点相比,自支撑点的流速较小,温度较高,换热性能更好。在流道中可以发现较强的螺旋形流动,螺旋流的强度随着扭矩的减小而增大,同时能在椭圆形截面处发现不规则的二次流,二次流的大小随着扭矩的减小而增大。

The fluid flow and heat transfer characteristics in the shell side of twisted tube heat exchanger were studied numerically with realizable k-ε model. The influence of the geometrical parameters of different twisted pitch lengths on the performance of the shell side was analyzed. The results reflect that Nusseh number and friction factor both decrease with the increasing of twisted pitch length. The influence of twisted pitch length on the shell side overall performance was also analyzed. It shows that the overall performance of the shell side firstly increases and then decreases with the increasing of twisted pitch length. The magnitudes of the total velocity at the self-supporting points were found to be lower and the temperatures were found to be higher than that of their neighborhoods. Spiral flow can be found in the shell side, and the intensity of the spiral flow becomes more and more drastic with the decreasing of twisted pitch length. The analysis of the secondary shows that the magnitude of the secondary flow decreases with the increasing of twisted pitch length. The irregular secondary flow can also be found around the helixes, which increases with the decrease of twisted pitch length.