Vibration in Nuclear Heat Exchangers Due to Liquid and Two-Phase Flow

In order to optimize a steam generator tube bundle support system, it is necessary to understand the differences in vibration behavior of tube arrays subjected to a two-phase flow regime as compared to a single phase flow regime. The relationships discussed in this paper are based on findings derived from a comprehensive vibration testing program which included both water and simulated two-phase (air-water) flow regimes. Tube bundles of various configurations and spacings were tested in crossflow using 3/4 in. (1.9 cm) and 7/8 in. (2.2 cm) o.d. tubes with 36 in. (91 cm) span lengths and as many as 40 tubes per array. Sufficient test loop capacity was provided to drive most test array configurations up to and beyond fluid-elastic instability. Parameters obtained included displacement, effective force coefficients, damping coefficients, Strouhal numbers, and instability constants for various tube array configurations in both liquid and simulated two-phase flow mediums.