Fluid Oriented Modeling Technology Of Branch Pipe And Junction In The Power Plant

The fatigue cracks usually occur on the connecting pipeline between the main and the branch in the power plant. To avoid the unfavorable influence of the fatigue cracks on the pipe junction, measures such as periodic maintenance and empirical analysis have been taken in the application occasions, the main solution is mending afterwards. As the condensate responsible for the crack, experimental and computational researches have been carried out in this article, furthermore numerical calculation is needed to simulate the flow and heat transfer, obtaining innovative results.Firstly, Aiming at studying the condensate refluxing and evaporation inside the atmospheric vent, the relative experimental research has been conducted and an experimental pipeline,simulating the pipeline layout in the power plant has been built. The experimental results show that superheated vapor never condensate and discharged directly when the atmospheric vent is 0.5m long, and the temperature of wall increases dominantly and tend to be even due to the vapor. In contrast, as the atmospheric vent has been prolonged to 3.5m, there is enough time for the heat exchange between the vapor and outside, thus the condensation happens. The condensate flows along with the inner wall of atmospheric vent and evaporates next to the junction. The thermal gradient at the place where the condensate evaporated threaten the junction.Secondly, a homogeneous phase change model has been built to simulate the process of phase change of the steam by CFX. After validation, the numerical results are in concordance with the experimental results, showing that this model can simulate the flow, heat transfer, phase change correctly.Thridly, On the basis of validating the feasibilities of CFD simulation, the change of liquid level at the drainage vent due to the steam pressure's fluctuation has been simulated. The results show that the condensate level in the drainage vent is determined by the frequency of pressure's fluctuation. So avoiding this factor is necessary.Fourthly, On the basis of validating the feasibilities of CFD simulation, different atmospheric vent layout in power plant have been analyzed. The results show that the optimum layout is the teminal should be vertically upward, the horizontal is a medium and the vertically downward is the worst.Fifthly, the steam condensation with the non-condensable gas has been simulated by Uchida model. The results show that Uchida model can calculate the non-condensable gas accumulation correctly, which is positive to study the accumulation of non-condensable gas in a small and simple physical model.The mathematical model built in this article can simulate the heat and mass transfer occurring in the steam condensation and evaporation accurately. Simultaneously, an optimum layout of the pipeline in the power plant was summarized, avoiding the shut down and tragedy by accident due to the leak. So CFD numerical simulation has vital social and economical values.