轴向力作用下换热管固有频率分析

Analysis of Natural Frequency of Heat Exchanger Tube under Axial Force

现有文献关于轴向力对换热管固有频率的影响系统性的研究较少。鉴于此,简要对比了TEMA标准、GB151及有限元法3种轴向力作用下换热管固有频率的计算方法,利用ANSYS软件瞬态激振计算与傅里叶变换相结合,分析了跨距l=1.0 m的等长多跨管在不同轴向力作用下前3阶固有频率变化规律。研究结果表明:轴向拉应力起到了应力刚化作用,使换热管固有频率升高,但拉应力的应力刚化效果要小于等值压应力的应力软化效果;轴向力对于换热管1阶固有频率影响较大,对于2阶和3阶固有频率的影响逐渐减小;对于跨距相等的多跨换热管,随着跨数的增多,轴向力对于固有频率的影响越来越明显。所得结论对于保证换热器的安全运行具有一定的指导作用。

Since there are lew papers systematically discussing the axial force influence on the heat exchanger tube natural frequency, TEMA standard, GB151 and finite element method have been briefly compared lor the nat-ural frequency calculation of the heat transfer tubes under the axial force. Based on the combination of transient ex-citation calculation of ANSYS software and Fourier transform, the variation law of the first three natural frequencies of l =1.0 m equal length multi-span tube under different axial forces has been analyzed. The results show that the axial tensile stress, with the stress stiffening effect, increases the natural frequency of the heat exchanger tube. But the stress stiffening effect of the tensile stress is less than the stress softening effect of the equivalent compressive stress. The axial force has great effect on the first order natural frequency of the heat exchanger tube, and gradually reduced on the second and third order natural frequency. For the multi-span heat transfer tubes with equal span,the influence of the axial force on the natural frequency increases more greatly with the increase of the span number.The conclusion could provide guidance for ensuring the safe operation of the heat exchanger.