The Numerical Simulation Of Heat Exchange Tube Bundle Based On Thermal Fluid-Structural Interaction

Shell-and-tube heat exchanger is widely used in various industrial applications by advantages of firm structure, flexible operation and high reliability etc. It directly affects the performance of the whole process of energy efficiency in many circumstances. The safety of heat exchanger has a great influence on industrial production operation. Heat exchange tube bundle is one of air heat exchanger components which more vulnerable to strength failure. Both thermal stress and fluid-induced vibration cause damage to the heat exchange tube easily. Therefore, the research of heat exchange tube bundle has a great significance for improving the life, efficiency and economic benefits of heat exchanger.A thermal fluid-structural interaction analysis model for air heat exchanger was established based on computational fluid dynamics by multi-physical field coupling method in this paper. The flow field analysis of both shell side and tube side was applied to the heat exchanger by FLUENT software. The data of flow field analysis was transferred to Mechanical module through the coupling walls, and loaded on the model of heat exchanger as loading boundary condition. Compared with different situations, it was found that the stress distribution of thermal fluid-structure interaction was related to the thermal stress distribution, the influence of fluid pressure was very small.According to the results of flow field simulation, the fluid exciting force was calculated and loaded on the simplified finite element model of a heat exchange tube. The results show that flow-induced vibration which caused by the vortex shedding, caused vibration and fatigue failure of the heat exchange tube.By using the dynamic grid technology and two-way coupling method, the shell side fluid and heat exchange tube bundle were analyzed. The results show that stress and deformation of tube bundle were very small with this velocity of fluid flow. The fluid elastic instability will not induce tube bundle vibration, and had little influence on tube bundle.In conclusion, the major reason of fatigue failure of air heat exchange tube bundle was the thermal stress which caused by temperature difference. However, the flow-induced vibration accelerated the failure of heat exchange tube bundle. The mechanism of flow-induced vibration was vortex shedding and turbulent buffeting. The tube bundle contacted with baffle, then formed the local stress concentration. During the vibration, the collision between the wall and baffle holes created the failure of tube bundle, until cracking.