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Wen Q.L.,Shanghai JiaoTong University | Wen Q.L.,Nuclear Power Institute of China | Gu H.Y.,Shanghai JiaoTong University
Annals of Nuclear Energy | Year: 2010

In this study, a numerical investigation of heat transfer deterioration (HTD) in supercritical water flowing through vertical tube is performed by using six low-Reynolds number turbulence models. All low-Reynolds models can be extended to reproduce the effect of buoyancy force on heat transfer and show the occurrence of localized HTD. However, most k- models seriously over-predict the deterioration and do not reproduce the subsequent recovery of heat transfer. The V2F and SST models perform better than other models in predicting the onset of deterioration due to strong buoyancy force. The SST model is able to quantitatively reproduce the two heat transfer deterioration phenomena with low mass flux which have been found in the present study. © 2010 Elsevier Ltd. All rights reserved. Source

Yang Q.,East China University of Science and Technology | Li Z.-M.,Nuclear Power Institute of China | Lv W.-J.,East China University of Science and Technology | Wang H.-L.,East China University of Science and Technology
Separation and Purification Technology | Year: 2013

Developments in different industries are leading to increased fine particles in industrial wastewater. Fine particle grading, separation, and recycling involve many problems, and the separation quality is directly related to the economic benefits and environmental effects. In this study, a mini-hydrocyclone with a nominal diameter of 25 mm was designed and tested for the separation of fine catalyst particles from water in the laboratory. The method was also used in the industrial methanol-to-olefin (MTO) quench water treatment process. Under certain feed conditions in the laboratory experiment, the separation efficiency of the mini-hydrocyclone was around 88% and the particle cut size d50 was 1.70 μm. The removal rate of particles larger than 3 μm reached ≥85%. The two stages of the mini-hydrocyclone separation process (i.e., clarification and concentrating) were examined, and the results showed that the process had high throughput and low loss. Recovery of MTO quench water by mini-hydroyclone and steam-stripping treatment were performed in an industrial plant. The cut size d50 in the industrial application was 1.68 μm, which was close to that in the laboratory experiment. The stripping process removed ketone and methanol, which are poisonous and harmful components that prevent MTO quench water recovery. Furthermore, catalyst particles larger than 5 μm were almost completely recycled. The recovery process of MTO quench water by mini-hydroyclone and steam-stripping treatment was successful. These results demonstrated that mini-hydrocyclone separation can be combined with other methods for the efficient treatment of industrial wastewater with fine particles. © 2013 Elsevier B.V. All rights reserved. Source

Yu D.,Tianjin University | Chen G.,Tianjin University | Yu W.,Nuclear Power Institute of China | Li D.,Guangdong University of Petrochemical Technology | Chen X.,Tianjin University
International Journal of Plasticity | Year: 2012

Experimental results of monotonic uniaxial tensile tests at different strain rates and the reversed strain cycling test showed the characteristics of rate-dependence and cyclic hardening of Z2CND18.12N austenitic stainless steel at room temperature, respectively. Based on the Ohno-Wang kinematic hardening rule, a visco-plastic constitutive model incorporated with isotropic hardening was developed to describe the uniaxial ratcheting behavior of Z2CND18.12N steel under various stress-controlled loading conditions. Predicted results of the developed model agreed better with experimental results when the ratcheting strain level became higher, but the developed model overestimated the ratcheting deformation in other cases. A modified model was proposed to improve the prediction accuracy. In the modified model, the parameter mi of the Ohno-Wang kinematic hardening rule was developed to evolve with the accumulated plastic strain. Simulation results of the modified model proved much better agreement with experiments. © 2011 Elsevier Ltd. All rights reserved. Source

Yu D.,Tianjin University | Chen X.,Tianjin University | Yu W.,Nuclear Power Institute of China | Chen G.,Tianjin University
International Journal of Plasticity | Year: 2012

Monotonic tension, isothermal/anisothermal fully reversed strain cycling and zero-to-tension cyclic tests were conducted within the temperature domain from room temperature to 823 Kto investigate the mechanical behavior of Z2CND18.12N austenitic stainless steel under various uniaxial loading conditions. Interesting results were observed from these tests, including obvious rate-dependence at room temperature but lack of rate-dependence at elevated temperatures with the occurrence of serrated flow stress in tensile tests, more cyclic hardening at higher temperature in strain cycling tests, and tendency to reach shakedown condition at elevated temperatures in zero-to-tension cyclic tests. Dynamic strain aging (DSA) effect was presumably believed to contribute to these characteristics of the material. A thermo-viscoplastic constitutive model was proposed to describe the mechanical behavior of the material under uniaxial loading conditions at small strains. Kinematic hardening rule with two components of back stress and isotropic hardening rule incorporating DSA effect are the novel features of the proposed model. The simulated and predicted results show reasonable agreement with the experimental data. © 2012 Elsevier Ltd. All rights reserved. Source

Chen X.,Nuclear Power Institute of China
Yuanzineng Kexue Jishu/Atomic Energy Science and Technology | Year: 2016

In order to develop high-performance fuel assemblies, resistance characteristics of spacer grid are directly related to thermal performance and hydraulic compatibility of fuel assemblies. Based on basic principles of flow resistance, the calculation model of local resistance characteristics for 5×5 spacer grids was studied and built by using CFD method and the calculation results were validated. The results show that the local resistance coefficients from calculation model are generally in agreement with those from direct simulation. © 2016, Editorial Board of Atomic Energy Science and Technology. All right reserved. Source

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