Numerical simulation of drainage performance in a drain device of steam generator

As the last stage of a moisture separator, the drain device is an important part of the secondary separator which can affect the separation efficiency. The emphasis of this paper is placed on studying the flow structure and predicting the free liquid surface height in the drain device. Four different turbulence models including k-ε, k-ω, Shear Stress Transport (SST) and Scale-Adaptive Simulation (SAS-SST) were used to simulate the drainage process with air-water mixture (cold state) under ambient temperature and atmosphere pressure. These models were validated by the experimental data obtained in our previous study. Simulation results showed that the free liquid surface height predicted by the SAS-SST model is in best agreement with the experimental results under cold state. Therefore it was further used to perform the simulation for steam-water mixture (hot state) under the standard working condition (138.1 m3/h, 7 MPa and 285.8 °C). The maximum free liquid surface height is simulated to be 269.3 mm for the hot state by the SAS-SST model which is 4.5% higher than that of the cold state. However, it could also meet the design object.