螺旋套管换热器大变形与热应力分析

Analysis of Large Deformation and Thermal Stress ofthe Helical Tube-in-Tube Heat Exchanger

采用“流-固”共轭传热与“热-固”单向耦合的方法,分析了螺旋套管换热器对流换热特性、热膨胀大变形以及对热应力计算的影响。结果表明:受离心力影响,螺旋管及夹层流体质点形成二次流混合强化螺旋外侧换热,螺旋内管外侧比同一截面内侧点温度更低;在高温换热工况下,在螺旋管因热膨胀而出现显著的变形,其变形量与管壁厚度处于同一数量级,高温工况下螺旋套管换热器热应力计算属于大变形问题,采用大变形有限单元非线性计算结果比小位移线性计算的热应力更大、更加符合实际。最后,以减小热应力为优化目标,对螺旋套管T型接头布置方位进行了优化,当接管径向布置时热应力比轴向布置减小约1/3。

Method of the“fluid-solid”conjugate heat transfer unidirectional coupling with“thermo-solid”was employed to ana-lyze convective heat transfer characteristics of the helical tube-in-tube heat exchanger,the thermal expansion and the influence of the large deformation on thermal stress calculation.The results show that fluid particles subjected to influence of centrifugal force of the helical tube and annulus generate secondary flow mixing and enhance heat transfer of the outer side of helical tube,temperature of the outer side of helical tube is lower than that of the inner side of the same section;under the high temperature heat transfer condition,the helical tube has significant deformation due to thermal expansion,and the deformation is at the same order of magnitude as thickness of the tube wall,and the thermal stress calculation of the helical tube-in-tube heat ex-changer belongs to the problem of large deformation,and the result of nonlinear calculation of large deformation finite element is larger than that of linear calculation of small displacement,and is more in line with the actual.Lastly,to reduce thermal stress as the optimization goal,the orientation of T-joint arrangement of helical tube-in-tube heat exchanger was optimized,the ther-mal stress of the radial arrangement T-joint is reduced by about 1/3 compared with that of the axial arrangement.