Study on two-phase flow instability in parallel multi-channels; Heiretsu tairyuro wo nagareru kieki nisoryu no nessui rikigakuteki fuantei ni kansuru kenkyu

With an objective to elucidate a flow instability phenomenon in an air-liquid two-phase flow flowing in a parallel multi-channel and accompanying boiling, experiments were carried out on a two-phase flow stability in parallel multi-channel systems having seven heating sections at maximum for the cases where the riser pipes are long and short. In the experiment, the stability boundary, the vibration cycle, and the vibration mode were investigated. The structure of the experimental device may summarized as follows: a test fluid having come out from a tank is sent into the heating section by a pump, where it boils, turns into an air-liquid two-phase flow, and enters into a steam drum passing through a riser pipe which is a visualizing section made of pyrex glass. The temperature at the heating section inlet can be adjusted by increasing or decreasing the cooling water flow rate, and opening and closing a bypass. The test fluid used is R-113. The investigations were performed on a parallel three-channel, a two-row four-channel, a parallel five-channel, a parallel six-channel, and a parallel seven-channel. Instability has developed under a condition that the quality is close to zero at the heating section outlet in any of the experiments. However, the shorter the riser pipe, the instability was more intense, and the vibration amplitude was smaller. 15 refs., 13 figs.