双肋椭圆扭管管内传热与流阻特性分析及其多目标结构优化

Research on Heat Exchange and Flow Resistance Performance and Multi-objective Structural ptimization of Oval Twist Tube with Two Fins

文中提出了一种具有两根对称排布的矩形内肋的椭圆扭管,并利用Fluent软件对目标换热管进行数值模拟.首先比较研究了双肋椭圆扭管、光滑椭圆扭管、圆管三者在雷诺数5 000至50 000时的流动与换热性能,对比分析了三者努谢尔数Nu、阻力系数f、流动传热综合评价指标PEC以及管内平均速度-温度梯度场协同角β.结果表明,双肋椭圆扭管较圆管具有更好的场协同度以及较好的综合流动换热性能.其次,研究了双肋排布角度α对椭圆扭管的流动与换热性能的影响.结果表明,不同的双直肋排布角度能够影响椭圆扭管内部的场协同度与综合性能.最后利用响应面结合多目标遗传算法(NSGA-Ⅱ),以努赛尔数增长率与流动阻力增长率为目标对截面参数进行优化,利用TOPSIS方法选出设计范围内最佳结构参数.

An oval twisted tube with two symmetrically arranged rectangular inner fins is studied in this paper.All the cases are numerically simulated by FLUENT software.Firstly, the flow and heat transfer performances of oval twisted tube with fins, smooth oval twisted tube and circular tube at Reynolds numbers from 5 000 to 50 000 are analyzed.The Nusselt number Nu,resistance coefficient f,comprehensive evaluation index PEC of flow and heat transfer and the synergy angle of average velocity temperature gradient field β of the tube were achieved.The results show that oval twisted tube with fins has better field synergy and better comprehensive flow and heat transfer performance than the circular tube.Secondly, effect of the arrangement angle of fins α is studied.The results show that different arrangement angles of double straight ribs can affect the field synergy and comprehensive performance in the elliptical twisted tube.Finally, to find the best section parameters, the response surface combined with multi-objective genetic algorithm(NSGA-Ⅱ) is used to optimize the growth rate of Nusselt number and flow resistance, and the TOPSIS method is used to select the best structural parameters in the design range.