Two-phase cross-flow-induced vibration of tube arrays

Many heat-exchange tubes in a shell and-tube heat exchanger are oscillated by means of the flow of fluid through the heat exchanger. This flow is often cross flow and gas-liquid two-phase flow. Here, a brief review of studies on two-phase cross-flow-induced vibration is presented, and a summary of our work in this area provides a design methodology. Three types of vibration have been studied for tubes in two phase cross-flow conditions: First, resonance of a tube due to vortex shedding is important primarily in single-phase flow, but also has been observed in homogeneous flow and even in two-phase flow. However, this vibration disappears in the slug flow or froth flow regions, which are important in numerous heat exchangers. Therefore, the vortex shedding phenomenon is not considered in this paper. Secondly, turbulent buffeting vibration is considered as the dominant phenomenon in the slug flow and froth flow regions. A method for estimating this type of random vibration is explained in this paper. Thirdly, an unstable form of vibration, so-called fluid elastic vibration, is also considered. The common method for estimating the instability boundary is similar to that used for single-phase flow; however, new insights on the method for two-phase flow are given in this paper.