【作者】 朱雨峰；

【导师】 谭蔚；

【作者基本信息】 天津大学 ， 化工过程机械， 2007， 硕士

【摘要】 管壳式换热器中管子是最具弹性的部件,因此在流体流动而激发起的振动中,是最容易引起振动的部位。GB151-1999附录E中针对光滑管的管束振动已有了很明确的计算方法。然而为提高传热效能,翅片管在换热器中得到了广泛的应用。对于翅片管固有频率,标准中只给出近似的计算方法。本文依据GB151、TEMA设计标准,针对翅片管的振动特性进行了研究。为此,本文采用有限元方法对翅片管模型进行模拟计算,通过模态分析和谐响应分析得出翅片管的固有频率和相应的位移响应;并应用强迫共振法试验测量了翅片管两端固支情况下的固有频率,验证了有限元计算结果。同时通过经验公式估算值与有限元计算值的比较,分析了各种经验公式的优劣。分析结果表明:翅片会引起管子的质量增加和刚度加强,在同等直径等壁厚的情况下,对于本文试验中用到的翅片管,其固有频率比光管低20%左右;翅片对管子的固有频率的影响体现在翅片间距、翅片厚度和翅片高度上,单独改变翅片间距,翅片高度或翅片厚度,固有频率近似呈线性变化。本文在求解翅片管的固有频率时,引入了当量外径和高度系数的概念,提出高度系数是翅片间距、翅片高度、翅片厚度的函数。并利用有限元模拟数据通过最小二乘法拟合出高度系数的计算公式,即T-Z-N式。利用该式得到的计算结果与有限元结果比较,单跨管最大误差为4.18%,多跨等跨管的误差为7.56%,多跨不等跨管的误差为4.71 %。该结果表明,T-Z-N式能较好地计算出翅片管的固有频率,而且适合于单跨管和多跨管。这些研究结果为翅片管的自振特性和防振技术的研究提供了依据,对于工程设计有一定的参考价值。更多还原

【Abstract】 The tube bundles applied in the shell and tube heat exchanger, due to high flexibility, are more likely to cause vibration failure than other components when excitated by fluid. Traditionally, the vibration of bare tube bundles has been studied and calculation methods have been given in GB151-1999. Nowadays, finned tubes are widely used in heat-exchanger to increase heat-transfer efficiency. However, there are only a few approximate formula for the vibration of finned tube in the standard.In this paper, based upon GB151 and TEMA standard, the vibration of finned tube is studied. A series of finned tube modals with different geometric parameters has been established by the finite element method(FEM), through modal analysis and harmonic response analysis,the natural frequency(NF) and corresponding modal shapes of each modal have been obtained. A driven resonance method has been applied to measure the NF of finned tube with two ends completely fixed, which give a verification to FEM results. Meanwhile, comparison has been done between the results of FEM and each approximate calculation method, and each calculation method has been estimated.It is concluded that the fins contribute to both the mass and stiffness of the tubes. With the same outside diameter, wall thickness and tube length, the NF of the finned tube sample in the experiment is approximately 20% lower than that of the bare tube. The geometric parameters of the fins including fin pitch, fin height and fin width have a strong influence on the NF of the tube. It is shown that there is approximately linear relationship between NF and each fin geometric parameter.In this article, the concept of the fin height coefficient and the equivalent outside diameter is introduced, and the least square method has been applied to fit the functional relationship between fin height coefficient and fin geometric parameters by using FEM results, thus the T-Z-N formula has been obtained. The NF calculated by this formula is compared with FEM results, and the maximum error is displayed: single span, 4.18%; multi-span(equal span), 7.56%; multi-span(unequal span), 4.71%. It’s shown that the formula can be used to calculate the NF of finned tube both in single span and multi-span, and provide a reference on the engineering.更多还原