Large eddy simulation on the turbulent mixing phenomena in 3×3 bare tight lattice rod bundle using spectral element method

Ju, Haoran,Wang, Mingjun,Wang, Yingjie,Zhao, Minfu,Tian, Wenxi,Liu, Tiancai,Su, G.H.,Qiu, Suizheng Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.9

Subchannel code is one of the effective simulation tools for thermal-hydraulic analysis in nuclear reactor core. In order to reduce the computational cost and improve the calculation efficiency, empirical correlation of turbulent mixing coefficient is employed to calculate the lateral mixing velocity between adjacent subchannels. However, correlations utilized currently are often fitted from data achieved in central channel of fuel assembly, which would simply neglect the wall effects. In this paper, the CFD approach based on spectral element method is employed to predict turbulent mixing phenomena through gaps in 3 × 3 bare tight lattice rod bundle and investigate the flow pulsation through gaps in different positions. Re = 5000,10000,20500 and P/D = 1.03 and 1.06 have been covered in the simulation cases. With a well verified mesh, lateral velocities at gap center between corner channel and wall channel (W-Co), wall channel and wall channel (W-W), wall channel and center channel (W-C) as well as center channel and center channel (C-C) are collected and compared with each other. The obvious turbulent mixing distributions are presented in the different channels of rod bundle. The peak frequency values at W-Co channel could have about 40%-50% reduction comparing with the C-C channel value and the turbulent mixing coefficient β could decrease around 25%. corrections for β should be performed in subchannel code at wall channel and corner channel for a reasonable prediction result. A preliminary analysis on fluctuation at channel gap has also performed. Eddy cascade should be considered carefully in detailed analysis for fluctuating in rod bundle.

Separation of Cu, Co, Ni and Mn from acid leaching solution of ocean cobalt-rich crust using precipitation with Na2S and solvent extraction with N235

Ju Jinrong,Yali Feng,Haoran Li,Hao Wu,Shunliang Liu,Chenglong Xu,Xin Li 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.3

In order to effectively separate and recover copper, cobalt, nickel and manganese from the leaching solution of ocean cobalt-rich crusts, a process of selective precipitation and extraction using precipitation with Na2S solution and solvent extraction with N235 extractant, was proposed. The optimum separation and recovery process conditions were determined through single factor condition experiments. The results show the precipitation efficiency of copper can reach 99.87%, while the precipitation efficiency of cobalt and nickel was 1.23% and 1.08%, respectively, at the initial pH of 0.60. Similarly, under the condition of initial pH of 4.00, 99.18% cobalt and 98.31% nickel were precipitated and only 0.89% manganese was co-precipitated. The mixed cobalt-nickel precipitation was completely dissolved with HCl solution, then N235 extractant was used to extract cobalt from solution. The extraction efficiency of cobalt can exceed 99% though three stages countercurrent extraction under optimal extraction conditions (chloride ion concentration of 9mol/L, the N235 concentration of 30% (v/v), the phase ratio (O/A) of 2, and at 298.15 K for 8min). In addition, thermodynamic calculations showed that the extraction of cobalt from acid leaching solution of ocean cobaltrich crust with N235 as the extractant was an exothermic reaction.

Effective separation of Zn, Fe, and Mn from roasting-water leaching solution of blast-furnace dust using a precipitation-solvent extraction process

Jinrong Ju,Yali Feng,Haoran Li,Ben Wang 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.12

Selective extraction of Zn from blast furnace dust can be achieved by the ammonium sulfate roasting-waterleaching process. An innovative method for effective separation of Zn, Fe, and Mn from roasting-water leaching solutionof blast-furnace dust by precipitation-solvent extraction process is proposed in this research. The Fe of leachingsolution was selectively converted into FePO4·2H2O precipitate by using Na2HPO4 as precipitant. The precipitation efficiencyof Fe reached 99.17%, while that of Zn was only 0.20% under the solution pH of 2.2, molar ratio of Na2HPO4 toFe of 1.2 : 1, reaction temperature of 30 oC, and reaction time of 50 min. The zinc in the filtrate was extracted with Cyanex302, and Zn (99.94%) was extracted through two-stage countercurrent extraction under initial pH of 3.4, Cyanex302 concentration of 25%, and O/A of 2 : 1. Subsequently, Zn (99.96%) of the organic phase was stripped using 0.75mol/L sulfuric acid by one-stage countercurrent stripping. Furthermore, according to thermodynamic calculation, it isproved that extracting Zn from sulfuric acid solution with Cyanex 302 is an exothermic reaction. The proposed processflowsheet may be used to efficiently recover Zn and Fe from blast-furnace dust.

Stress sensitivity in naturally fractured reservoirs: a case study of the Lower Cretaceous Xiagou Formation, Qingxi Oilfield, Jiuxi Basin, northwestern China

Wei Ju,Xiaolong Fu,Weifeng Sun,Haoran Xu,Shengyu Wang 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.3

Stress sensitivity is the variation of rock petrophysical parameters resulting from changes in effective stress. In fractured reservoirs, experimental methods exhibit a certain amount of error in the quantitative analysis of reservoir rock stress sensitivity. In addition, fracture-bearing experimental rock samples are difficult to obtain and prepare. Therefore, in the present study, reservoir rock stress sensitivity in naturally fractured reservoirs was investigated based on geomechanical modeling using a case study of the Lower Cretaceous Xiagou Formation in the Qingxi Oilfield. The results indicate that the Xiagou fractured reservoir experiences strong stress sensitivity with a fracture permeability damage rate reaching 94.38%. Natural fractures influence reservoir rock stress sensitivity. The degree of filling and type of filled minerals within natural fractures have great effects on the permeability damage rate. A higher permeability damage rate suggests stronger rock stress sensitivity. Generally, I) for reservoir rocks with unfilled natural fractures, the permeability damage rate is extremely high; II) for reservoir rocks with partially filled natural fractures, the permeability damage rate is high, and if the minerals within the natural fractures are insoluble, the permeability damage rate is slightly higher than if the materials are soluble; III) for reservoir rocks with completely filled natural fractures, the permeability damage rate is extremely low if the minerals within the natural fractures are insoluble; however, if the materials are soluble, the permeability becomes slightly higher with the increase of effective stress. Most importantly, this study provides a practical method for analyzing stress sensitivity in naturally fractured reservoirs.

PIV measurement and numerical investigation on flow characteristics of simulated fast reactor fuel subassembly

Zhang, Cheng,Ju, Haoran,Zhang, Dalin,Wu, Shuijin,Xu, Yijun,Wu, Yingwei,Qiu, Suizheng,Su, G.H. Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.5

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

Numerical Simulation of the Creep Behavior of Beishan Deep Granite Tunnel under the Coupling Thermal -Stress Field

Jiawei Wang,Ju Wang,Zhichao Zhou,Peng Wu,Haoran Sun,Jiale Dou,Nan Li,Xianzhe Duan 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.4

This study conducts a three-dimensional numerical simulation of the creep behavior of deep granite tunnels at 560 meters underground during the coupled thermal-stress process, with an aim to elucidate the effect of the temperature and stress fields on the creep behavior of these deep hard rock tunnels. A 100-h creep period was set, and the mechanical structure of the experimental chamber was accurately replicated at a 1:1 scale, considering the actual mechanical structure of the granite tunnels in the Beishan underground laboratory. The simulation results can demonstrate that: 1) The maximum stress at 90°C and 50°C are 2.86 and 1.91 times than that at 23°C, respectively, demonstrating significant strain accumulation in the deep granite tunnels at the surface. This phenomenon can primarily be attributed to the thermal stress resulted from the coupling between temperature and stress. 2) The maximum creep at 90°C and 50°C is 16 and 3.5 times than that at 23°C. Under the influence of thermal coupling, the creep increases significantly with increasing temperature, indicating that temperature is an important factor influencing creep in granite. 3) Compared with variations in the stress field, the temperature field emerges as the most critical factor influencing granite creep.

CFD simulation of flow and heat transfer characteristics in a 5×5 fuel rod bundles with spacer grids of advanced PWR

Wang Yingjie,Wang Mingjun,Ju Haoran,Zhao Minfu,Zhang Dalin,Tian Wenxi,Liu Tiancai,Qiu Suizheng,Su G.H. 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.7

High fidelity nuclear reactor fuel assembly simulation using CFD method is an effective way for the structure design and optimization. The validated models and user practice guidelines play critical roles in achieving reliable results in CFD simulations. In this paper, the international benchmark MATiS-H is studied carefully and the best user practice guideline is achieved for the rod bundles simulation. Then a 5 5 rod bundles model in the advanced pressurized water reactor (PWR) is established and the detailed three-dimensional thermal-hydraulic characteristics are investigated. The influence of spacer grids and mixing vanes on the flow and hear transfer in rod bundles is revealed. As the coolant flows through the spacer grids and mixing vanes in the rod bundles, the drastic lateral flow would be induced and the pressure drop increases significantly. In addition, the heat transfer is enhanced remarkably due to the strong mixing effects. The calculation results could provide meaningful guidelines for the design of advanced PWR fuel assembly

Investigation on the mechanism of ring formation in the process of NaCl recovery by pyrolysis of chemical waste salt using rotary kiln

Wenyuan Wang,Yali Feng,Haoran Li,ShunLiang Liu,Jinrong Ju,Yi Yang,Ben Wang 대한환경공학회 2023 Environmental Engineering Research Vol.29 No.3

Chemical waste salt is a hazardous waste generated during chemical production, and it is crucial to complete the recycling of the waste salt in a practical way. In the case of waste salt recycling by rotary kiln pyrolysis carbonization, ringing affects the pyrolysis efficiency and process running, thus a study on waste salt ringing was conducted. The results showed that the particle size is the key to the ring formation in rotary kiln, and pyrolysis temperature, pyrolysis time and temperature distribution in the rotary kiln also affect the material discharge rate during pyrolysis of waste salt in the rotary kiln. Thermogravimetric analysis and SEM images revealed that the volatilization of organic matter in the material due to pyrolysis caused a decrease in the abrasion resistance of the waste salt particle, which was the factor behind the ringing during pyrolysis in the rotary kiln. This study may provide a reference for the implementation of similar waste salt pyrolysis carbonization processes.