Measurements of void concentration parameters in the drift-flux model

To predict accurately the thermal hydraulic behavior of light water reactors during normal or abnormal operation, the accurate estimation of the void distribution is required. Up to date, many techniques for predicting void fraction of two-phase flow systems have been suggested. Among these techniques, the drift-flux model is widely used because of its exact calculation ability and simplicity. However, to get more accurate prediction of void fraction using drift-flux model, slip and flow regime effects must be considered more properly. In the drift-flux method, these two effects are accounted for by two drift-flux parameters; Co and V-bargi. At earlier stage, Co is measured in a circular tube. In this study, Co is experimentally determined by measuring local void fraction and vapor velocity distribution in a rectangular subchannel having 4 heating rods which simulates nuclear subchannels. The measurements are performed with two-electrical conductivity proves which are known to be adequate for measuring local parameters. The experiments are performed at low flow rate and the system pressure less than 3 atm spheric pressure. In this experiment, V-bargi is not measured, but quoted from well-known empirical correlation to formulate Co. Finally, Co is expressed as a function of channel averaged boid fraction. (Author)