Basic Flow Characteristic of Inverted Churn Gas-liquid Two-phase Flow Obtained by Optical Flow Method

In thermohydraulic safety analysis for heating pipe in boilers and nuclear reactors, inverted-churn flow is commonly formulated due to high-temperature wall. In such flow, liquid ligaments fly upward and downward in the gas core flow and the cooling liquid cannot contact with the wall so that severe wall damage might occur by its low heat transfer. In this study, an inverted-churn flow was formulated in vertical 20-mm diameter pipe coated with water-shedding material. The basic flow characteristics of ligaments in the floww were measured and discussed using the stereo image-processing method and the optical flow method.