Effect of the surface tension correction coefficient on the nonequilibrium condensation flow of wet steam

Abstract

In view of the nonequilibrium characteristics of water vapor in the condensation process, various models have different degrees of deviation in the prediction of the condensation process. Water droplet surface tension appears in the exponential term of the nucleation rate in the form of a third power, which has a significant effect on the distribution of parameters such as condensation location, water droplet number and wetness. In order to improve the accuracy of numerical simulation, the correction coefficient is used to modify the plane surface tension calculation model. The nonequilibrium condensation process in the Moses-Stein nozzle is simulated. By comparison with the experimental data, the influence of the surface tension correction coefficient on the calculation accuracy of the model is analysed. The functional relationship between the superheat at the steam inlet and the optimal surface tension correction coefficient is obtained. After correction, the error between the simulation results and the experimental values of each working condition of the nozzle is reduced to less than 2%. In addition, this conclusion is verified by the nonequilibrium condensation flow in the turbine cascades. The deviations between the three simulation results and the experimental values are 1.86%, 2.10% and 1.88% respectively, and the simulation accuracy is significantly improved. The results show that with the increase in the surface tension correction coefficient, condensation will be inhibited under the same working conditions. There is an optimal value of the correction coefficient. Under different working conditions, there is a significant positive correlation between the optimal surface tension correction coefficient and the inlet superheat. It can significantly improve the simulation accuracy by using the corrected surface tension value. The results can provide a reference for the calculation of wet steam condensation flow.