Calculation of Lateral Contact Stiffnesses of Tubes in Tube Bundle Heat Exchangers

Tubes in tube bundle heat exchangers are subject to flow-induced vibration. The tubes are supported by baffles. Between tubes and baffles there is a gap where fretting wear occurs due to the movement of the tubes. The contact stiffness between tube and baffle support due to tube ovalization is of great relevance both for fretting wear analysis and for numerical simulation of the tube bundle dynamics regarding fluidelastic instability. In the present paper lateral contact stiffnesses are calculated by the method of Finite Elements and the results are compared to experimental results. Some deviations between numerics and experiment can be explained by regarding geometric tolerances of the experimental setup. Analytical formulae for stiffnesses under variation of the angle of attack can be derived from FEM results. The results can be used to improve simulation of tube bundle dynamics using an inhouse code for flow-induced vibration in tube bundle heat exchangers. Numerical simulation results show the significant influence of the lateral contact stiffness on the global vibrational behaviour of the tubes and their lifetime duration.