Flow Regime Visualization of Wet Steam Flow in a Horizontal Circular Pipes Having Different Diameter

Abstract To evaluate the occurrence conditions and rate of progression of flow-induced aging degradation phenomena such as pipe wall thinning and vibration fatigue in steam piping systems, it is essential to accurately understand the steam flow conditions inside pipes. However, the flow structure (flow pattern and sound velocity) of water-steam two-phase flow under high steam quality conditions is not sufficiently clear at present, and the occurrence and progression of degradation phenomena may not be properly evaluated. In this study, the pattern of water-steam two-phase flow under high-steam-quality conditions was visually observed to clarify the flow pattern. The database of flow patterns under a wide range of conditions was constructed by expanding the data, especially in the annular dispersed flow region for systems with pipe inner diameters of about 40 mm, and by acquiring new flow visualization data for piping systems with pipe inner diameters larger than 40 mm. It was shown that the existing flow regime maps can be used to determine the flow pattern of wet steam flow through comparison with existing flow regime maps of water-air two-phase flow, thereby improving the reliability of the flow pattern determination method.