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

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 45 mm to 57.5 mm, the excessive local membrane stress can be avoided.