This paper reports the results of a study of two-phase cross-flow excitation of a tube array comprised of heated tubes in Freon-11, with vapour being generated both upstream of the test array and at the tube surfaces themselves. These experiments simulate flow excitation in real steam generators more realistically.
Special cartridge heaters were arranged in a cantilevered parallel triangular array with a pitch ratio of 1.49. Tube response was monitored in a non-obtrusive way using an optical technique developed for this purpose. Experiments were conducted under isothermal conditions for comparison with similar cases in which nucleate boiling occurred on the tube surfaces. The results indicate that the effect of vapour generated at the tube surfaces is to: a) reduce the tube vibration amplitude, mainly in the transverse direction and, b) increase the void fraction needed to reach fluidelastic instability.