Random excitation forces in heat exchanger tube bundles

Random excitation forces can cause low-amplitude tube motion that will result in longterm fretting-wear or fatigue. To prevent these tube failures in heat exchangers, designers and troubleshooters must have guidelines that incorporate random or turbulent fluid forces. Experiments designed to measure fluid forces were conducted at the Chalk River Laboratories and at other laboratories worldwide. The data from these experiments were studied and collated, to determine suitable guidelines for random excitation forces. In this paper, a guideline for random excitation forces in single-phase cross flow is presented in the form of normalized spectra that are applicable to a wide range of flow conditions and tube frequencies. In particular, the experimental results used in this study were conducted over the full range of flow conditions found in the liquid region of a nuclear steam generator. The proposed guidelines are applicable to steam generators, condensers, reheaters and other shell-and-tube heat exchangers. They may be used for flow-induced vibration analysis of new or existing components, as input to vibration analysis computer codes and as specifications in procurement documents.