绕管式换热器管板的有限元应力分析与结构优化

Finite element analysis and structural optimization of tubesheet in coil-wound heat exchanger

绕管式换热器广泛应用于大型天然气液化装置,而管板是绕管式换热器的重要组成部件。由于管板处于管程、壳程交界处且布有密集的孔洞,降低了结构强度,使其成为LNG绕管式换热器的相对薄弱部位。利用Ansys有限元计算软件,对LNG绕管式换热器管板及其相连的管箱、换热器壳体进行整体建模和多工况下的有限元应力分析,并根据JB4732—1995进行强度校核。计算结果显示,换热器壳体对管箱短节部分的应力有较大影响;实例中换热器外壳的拉伸作用导致短节内侧局部薄膜应力过大,超出许用强度。增加短节厚度可以有效提高管箱强度;通过将原短节厚度由45 mm增加到57.5 mm,解决了局部薄膜应力过大的问题。

The coil-wound heat exchanger is widely used in large-scale liquefied natural gas(LNG)installations.The tubesheet is an important component of the coil-wound heat exchanger.Due to the fact that the tubesheet is located at the junction of the tube-side and the shell-side and the densely holes reduce the structural strength,the tubesheet is a weak part of the LNG coil-wound heat exchanger,and a prediction model of the stress on the tubesheet is needed to check the stress intensity.In this paper,a model of tubesheet unit including short section,shell cover and shell of heat exchanger is developed and finite element calculations of tubesheet under multiple working conditions are carried out by Ansys.The stress intensity is checked according to JB4732-1995.The modeling results show that the tensile stress inside the shell causes the large local membrane stress at the short section connected to the tubesheet due to the shell-side fluid pressure acting on the shell of the heat exchanger,and the local membrane stress exceeds the allowable stress intensity.By increasing the thickness of the short section of the tubesheet from 45mm to 57.5mm,the excessive local membrane stress can be avoided.