Ayao Tsuge

An experimental study on drift flux parameters for two-phase flow in vertical round tubes

Correlations which can correctly express the velocity difference between steam and water of two-phase flow are required for accurate predictions of the thermal-hydraulic transient behaviour for a pressurized water reactor (PWR) power plant during a small break loss-of-coolant accident (LOCA). A drift flux model is one of the typical models which describes the relative velocity between the two phases. A number of empirical expressions of the parameters for the drift flux model have been proposed based on experiments. It is necessary to confirm whether those formulas are applicable to the simulation of two-phase flow behaviour in a large scale apparatus such as the actual PWR plant. In this study, the experiments of cocurrent and counter-current steam-water two-phase flow using a large scale apparatus with 0.1023 m diameter tubes, and small scale apparatus with 0.0197 m diameter tubes were carried out. This paper presents the tube diameter effects on the drift flux parameters (Co = distribution parameter and Vgj = drift velocity). In addition, new empirical correlations of the drift flux parameters for the two-phase flow in large diameter tubes are proposed. A root mean square error of the predicted void fraction is 16.8% compared with 1353 experimental data.

Small break loch experiments and verification of CANAC-II code

Abstract Scaled experiments on small break, loss-of-coolant accidents have been conducted. The tests simulated loss-of-coolant accidents (LOCAs) resulting from a 0.53% and a 0.13% communicative break in the cold leg and the pressurizer power operated relief valve (PORV). The thermal-hydraulic behavior such as natural circulation and reflux condensation cooling during a small break LOCA has been investigated. A new computer program CANAC-II (a Computer Analysis Program of Natural Circulation for multi-loop systems) has been developed and verified based upon comprehensive tests. A drift flux model was applied for two-phase flow in CANAC-II. It also has a shorter computer running time than the real time.