An Experimental Study on the Damping of a Steam Generator Tube With Gap Supports in Air and Water

In this study, we present an analysis and experiment on the fluid damping of a Steam Generator (SG) tube with one and several plate-type supports that are submerged under water. For the damping measurement, a short tube of 2.2 meters in length with one gap support as well as a long tube of up to 10 meters with 11 and 13 supports are used. To see a fluid effect through an analytical approach, Mulcahy’s theory on a tube with finite-length gap support and Pettigrew’s empirical correlation for SG design were reviewed. The theoretical model is good at predicting the fluid damping at the first mode in a low frequency range which is an inactive mode at the support, while the practical model is much better at the higher modes, which are active modes, rocking modes, at the support(s). Experimental results from the short length tube with single support shows good agreement with a previous measurement by other researchers. A theoretical model and empirical correlation are in good agreement. Our measurements from a longer tube with several supports are reasonable compared with the others. There is, however, a wide discrepancy between predictions by the two models. As compared with the whole measurements, the theoretical model seems to be a good guideline in a low frequency range, while an empirical model is relatively good guideline in a high frequency range. Based on the whole collected data, a new correlation modified from Pettigrew’s correlation is suggested.