Quality measurement of two-phase flow in plug flow region.

In refrigeration cycles, quality measurement of two-phase refrigerant flow is sometimes required especially at an injection line of injection cycles. Although void fraction of the two-phase flow at a certain section of the pipe can be detected, the quality of the two-phase flow is not obtained from the sectional void fraction when there is velocity difference between the liquid phase and the gas phase. In case of a horizontal two-phase flow through a narrow tube with flow pattern of plug flow, the velocities of the liquid and the gas are thought to be almost the same. Therefore, the quality of the two-phase flow can be derived from the void fraction of the plug flow. In this study, the condition under which the flow pattern becomes the plug flow in the narrow tube is considered. The feasibility of the quality measurement based on the void fraction measurement is shown both in water-air two-phase flow and refrigerant two-phase flow.