Papers by Author: Chang Qi Yan

Abstract: To provide steam of appropriate quality and to improve the efficiency of steam-water separation over corrugated plates, it is necessary to study the condensation behavior of wet steam moving over a corrugated plate separator. In this paper, classical nucleation theory and a droplet growth model are used to describe the process of wet steam condensation on corrugated plates. The CFX software water droplet condensation model was employed to simulate the process and to allow analysis of the characteristics of wet steam condensation. The results show that: (1) the nucleation rate increases gradually over time and exhibits a positive correlation with the temperature of the wet steam, (2) departure from the saturated state decreases gradually along the flow direction, leading to a concurrent decrease in the steam condensation rate and (3) the steam condensation rate is elevated with increases in the local pressure gradient.

Abstract: In order to improve the inherent safety of the Molten Salt Reactor (MSR), a concept of passive residual heat removal system (PRHRS) for the 10MW Molten Salt Reactor Experiment (MSRE) was put forward. Its transient characteristics were investigated by developing a model of it using C++ code. The effects of environmental temperature, finned tube number and chimney height on the PRHRS were analyzed. The results show that the PRHRS can remove the decay heat timely. Three natural circulations are established in the PRHRS when it begins to operate. With the decay heat power reducing, the PRHRS can automatically adjust its heat removal ability. It needs not any external power for the PRHRS to operate, which enhances the inherent safety and reliability of the reactor, especially under the condition that power plants lose power.

Abstract: A series of BiOCl photocatalysts with different AgCl contents have been synthesized by a simple hydrolysis method at room temperature using BiCl3 and Bi(NO3)3•5H2O as the main raw materials. The resulting products were characterized with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV‐vis diffuse reflectance spectra (DRS). The photocatalytic activities of these AgCl/BiOCl composites were evaluated by the degradation of rhodamine B (RhB) under UV and visible light. The results revealed that the BiOCl/AgCl with an initial 100:1 mole ratio of Bi to Ag have the highest photocatalytic activity. RhB (20 mg/L) was decolorized by 98.81% in 15 min under sun light, in contrast to 95.89% and 11.63% in 30 min under halogen lamp and UV light, respectively. The catalysts did not show any significant loss of activity after 19 recycles for the photodegradation of RhB, suggesting the photocatalyst is essential stable. Kinetic studies showed that the RhB photocatalytic degradation followed pseudo-first order kinetics reaction and fit the Langmuir-Hinshelwood kinetic equation. The rate controlling step was absorption reaction.

Abstract: In nuclear power plant (NPP), particulate matter and gaseous pollutant release into the environment in severe accidents. To prevent from this disaster, filtered vented containment system (FVCS) containing venturi scrubber is being installed. The present work herein is the CFD simulation of throat pressure in venturi scrubber. A commercial software ANSYS CFX tool has been selected for this research. Euler-Euler regime is used to get the picture of behavior of fluid dynamics inside the venturi scrubber. Gas and liquid interact with each other in throat section of venturi scrubber. The pressure at the throat is one of the important factors to analyze the performance of venturi scrubber. In order to verify the results, mesh independency is checked. CFX and experimental results show good agreement with each other. The results obtained from CFX simulation are useful to improve the venturi design.

Abstract: Venturi Scrubbers are used in filtered vented containment system (FVCS) for collection of aerosols produced in NPP in severe accidents. Therefore, venturi scrubber (VS) needs an attention to design it properly and improved in all aspects. In this research, CFD simulations of prediction of pressure drop in venturi scrubber has been carried out. ANSYS CFX tool is used to obtain the simulation results. k-ε turbulence model is employed to study the fluid dynamics of the venturi scrubber. Mesh size plays an important role for convergence and accuracy of results. Therefore, the mesh independency is checked for optimized mesh size.