双向扭曲管传热与流阻特性及其多目标优化

以水为工质,对双向扭曲管湍流状态下传热与流阻特性进行数值计算和准确性实验验证,分析了其强化换热机理及截面尺寸a与导程S对其传热流阻的影响,并在其基础上对双向扭曲管结构参数进行多目标优化以及努塞尔数和阻力系数的关系式拟合。结果表明:相同工况下,双向扭曲管的综合换热性能优于光管和扭曲管,在Re小于20 000时具有较好的强化效果,且高出扭曲管3.92%;流体旋转流动的方向周期性改变,进一步强化了对流传热;当a增加到一定程度,管内的湍流程度不再增加;相同Re下,η、Nu和f对导程S的变化反应较灵敏。在Re=2 300～20 000、介质为水时,拟合关系式具有较高的准确性,且通过优化得到了结构的最优组合。

Heat transfer and flow resistance characteristics of bidirectional twisted tube and multi-objective optimization

Using water as the working medium, studying the heat transfer and flow resistance properties of the bidirectional twisted tube in turbulent flow and the accuracy of the experimental verification, analyzing the effect of the heat transfer mechanism and the influence of a and the S on its heat transfer resistance, on the basis of which,multi-objective optimization and relational expression of nusselt number and resistance coefficient are done. The results show that: Under the same conditions, the PEC of bidirectional twisted tube is better than that of the smooth pipe and the twisted tube and higher than the twist tube 3.92%. when Re is less than 20000, it has better strengthening effect; The direction of the fluid rotation flow is periodically changed, the convective heat transfer is further strengthened; When a increases to a certain extent, the degree of turbulence in the tube is no longer increased; In the same Re, PEC ,Nu and f are more sensitive to the change of S; In the case of Re = 2300 ~ 20000, the medium is water, the fitting relation has high accuracy and the optimal combinations of the structure is obtained by optimization