Yasuhiko Hirao

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.

Development of Moisture Separator With High Performance of Steam Generator

A steam generator of PWR plant has moisture separators with function to separate water from two-phase flow of water and steam. Recently, corresponding to the request for power uprating of current and/or future plants with large thermal capacity, development of high performance moisture separator, which can deal with the increasing steam flow rate, has been required. Therefore, MHI has developed the moisture separator with high performance (J Model) by conducting a verification test under actual plant operating conditions (high pressure and high temperature). The developed separator’s main features are: swirl vane hub with a small diameter, horizontal slits at riser barrel, and slots with lips at the downcomer barrel. Based on the combination of the high pressure test results and thermal hydraulic analyses, value of moisture carry over (MCO) at SG outlet was evaluated. The evaluation resulted in the MCO value of less than 0.01% (our target value: 0.1%).Copyright