수평관 및 경사관에서 기포율 및 속도 동시측정을 위한 임피던스 센서 개발

Abstract

Two-phase flow is a general phenomenon in a variety of industries including nuclear power plant. The void fraction and velocity in two-phase flow is one of the most important parameters associated with system analysis and design. For this reason, many techniques including gamma ray or X-ray absorption, ultrasonic wave, optical probe, and electrical impedance methods have been proposed. Among these instruments the electrical impedance technique has a variety of advantages such as easy implementation, no intrusiveness of flow field, no radiation, and convenient mobility. In the impedance sensor, the electrical signals depend on the flow structure as well as the void fraction. Therefore, the electrical responses to a given void fraction differ according to the flow pattern. In this study, An impedance sensor if developed to determine the flow pattern with the three electrodes, and at the same time, to measure the void fraction. In addition, through the parallel arrangement of two sensors, a velocity measurement is performed using the time-averaged void fraction correlation. Prior to the real applications of the proposed approach, several numerical calculations based on the finite element method(FEM) are performed to optimize the electrode and insulator sizes in terms of the sensor linearity and these are verified in comparison with the data from static experiments. Finally, the sensor system is applied to horizontal and near-horizontal loops and measuring performance for the void fraction and velocity is compared with that of a wire-mesh sensor and high-speed camera system.