Experiment Investigation on Onset of Flow Instability in Narrow Rectangular Channel under Low Pressure and Low Mass Flux Condition

The visualized experimental investigations were carried out on the phenomena of onset of flow instability (OFI) at low pressure and low mass flux condition in a vertical narrow rectangular channel with the section of 40 mm×3 mm. The bubble behavior and flow pattern distribution at OFI were visualized and then the mechanism of OFI was analyzed qualitatively. The effects of thermal-hydraulic parameters on OFI were preformed. Based on the experimental data, existing OFI predicted correlations were evaluated. The results show that the correlations, which adopt the parameters at saturation point as the independent variables, can predict the experimental data reasonably.