Numerical simulation of countercurrent flow in a scaled model of a pressurizer surge line

Numerical simulation was carried out for air-water countercurrent flows in a 1/10-scale model of the pressurizer surge line in a pressurized water reactor. The model consisted of a vertical pipe, a vertical elbow, and a slightly inclined pipe with elbows. In an actual 1/10-scale experiment, air supplied into the lower tank flowed up to the upper tank through the surge line and water supplied into the upper tank flowed down to the lower tank through the surge line. In the case of water supply into the upper tank in the simulation, the flow pattern in the inclined pipe was not reproduced because of flooding at the upper end of the vertical pipe with a sharp edge. To avoid effects of flooding at the upper end, therefore, water was also supplied from the wall surface of the vertical pipe and then the flow pattern in the inclined pipe was successfully reproduced. The simulated countercurrent flow limitation (CCFL) values agreed well with the experimental CCFL data.