Suchergebnisse

Passive safety system is the core feature of advanced nuclear power plant (NPP). It is a research hotspot to fulfill the function of passive safety system by improving the NPP natural circulation capacity. Considering that the flow behaviors of stopped pump pose a significant effect on natural circulation, both experimental and computational fluid dynamics (CFD) methods were performed to investigate the flow behaviors of a NPP centrifugal pump under natural circulation condition with a low flow rate. Since the pump structure may lead to different flows depending on the flow direction, an experimental loop was set up to measure the pressure drop and loss coefficient of the stopped pump for different flow directions. The experimental results show that the pressure drop of reverse direction is significantly greater than that of forward direction in same Reynolds number. In addition, the loss coefficient changes slightly while the Reynolds number is greater than 8 × 104; however, the coefficients show rapid increase with the decrease in Reynolds number under lower Reynolds number condition. According to the experimental data, an empirical correlation of the pump loss coefficient is obtained. A CFD analysis was also performed to simulate the experiment. The simulation provides a good accuracy with the experimental results. Furthermore, the internal flow field distributions are obtained. It is observed that the interface regions of main components in pump contribute to the most pressure losses. Significant differences are also observed in the flow field between forward and reverse condition. It is noted that the local flows vary with different Reynolds numbers. The study shows that the experimental and CFD methods are beneficial to enhance the understanding of pump internal flow behaviors.

AbstractIn 2016, China increased sustainability practices among companies listed on China's stock market, making environmental regulations one of their integral policies. This states that highly polluting industries like the energy industry are required to comply with the sustainability requirements set. Concerning this event, research was conducted in 2016 to 2017, on the development of environmental disclosure (ED) practices in China and the impact of different variables on environmental disclosure index (EDI). Focusing on 150 energy companies listed on the Shanghai and Shenzhen stock exchange, the findings show that if the company had a better ROA, firm size, leverage and environmental accreditation certificate, they would like to publish more relevant environmental information.