VIBRATION DAMPING OF HEAT EXCHANGER TUBES IN LIQUIDS: EFFECTS OF SUPPORT PARAMETERS

Damping information is required to analyse heat exchangers for flow-induced vibration. The most important energy dissipation mechanisms in heat exchanger tubes are related to the dynamic interaction between tube and support. In liquids, squeeze-film damping is dominant. Simple experiments were carried out on a two-span tube with one intermediate support to investigate the effects of support parameters, such as: support thickness, diametral clearance, tube eccentricity, tube span length, location of tube-support, and nature of dynamic interaction between tube and support. The results show that squeeze-film damping is much larger for lateral-type motion than for rocking-type motion at the support. Eccentricity was found to be very important. Diametral clearance, support thickness and frequency are also very relevant. The experimental results were compared to existing theories. A semi-empirical expression to formulate squeeze-film damping is proposed.