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Study of depressurization process for supercritical fluid

Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2015年第3期49卷 440-446页

作者： Zhang, Jing Tian, Wen-Xi Zhu, Da-Huan Qiu, Sui-Zheng Su, Guang-Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China School of Nuclear Science and Technology Xi'an Jiaotong Univesity Xi'an710049 China

The loss of coolant accident (LOCA) research of the supercritical water-cooled reactor (SCWR) is the key and difficult task for the safety analysis, and especially the research of the depressurization process of the pressure vessel is of crucial importance. The reactor pressure vessel was simplified and mathematical physics models were established in this study. A transient calculating code was developed. A comparison between experimental and calculated results for supercritical carbon dioxide was carried out. It is showed that the predicted results by codes are in good agreement with the experimental data. The depressurization process was analyzed by the verified code. The influences of different initial conditions, breach areas and heating powers on the depressurization process were discussed. The results show that the models established in this study can simulate the depressurization process from supercritical to subcritical state, and the calculating results may provide a theoretical basis for accident analysis of the SCWR. ©, 2015, Atomic Energy Press. All right reserved.

关键词： Supercritical fluids

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Prediction of flow boiling heat transfer coefficient in horizontal channel by genetic neural network

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Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2015年第1期49卷 70-76页

作者： Zhang, Jing Cong, Teng-Long Su, Guang-Hui Qiu, Sui-Zheng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an710049 China

The three-layer back propagation network (BPN) and genetic neural network (GNN) were developed to predict the flow boiling heat transfer coefficient (HTC) in conventional and micro channels. The precision of GNN is higher than that of BPN (with root mean square errors of 17.16% and 20.50%, respectively). The inputs include vapor quality, mass flux, heat flux, diameter and physical properties and the output is HTC. Based on the trained GNN, the influences of input parameters on HTC were analyzed. HTC increases with pressure in conventional channels. The pressure has a negligible effect at low pressure region on HTC for micro channels. However, at high pressure region, HTC increases in low vapor quality region, while decreases in the high vapor quality region with the increase of pressure. HTC increases with the mass flux and heat flux, and HTC initially increases and then decreases as vapor quality increases. HTC increases inversely with the decrease of diameter. Dry-out arises at a lower quality in micro channels than that in conventional channels and more easily occurs in a smaller channel. ©, 2015, Atomic Energy Press. All right reserved.

关键词： Heat transfer coefficients

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Visible light-driven water oxidation using metal oxide quantum dots modified with a cobalt catalyst

Visible light-driven water oxidation using metal oxide quant...

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中国化学会第九届全国无机化学学术会议

作者： Fujun Niu Ning Zhang Shaohua Shen Liejin Guo International Research Center of Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University

Conversion of sunlight to chemical fuels is the holy grail to deal with the energy and environment issue.1,2 Inspired by the natural photosynthesis, molecular based photocatalytic system has been widely investigated. Generally speaking, such a system contains three part: a sensitizer to absorb light, a reduction catalyst to generate H2, and an oxidation catalyst to produce O2. The oxidation of water has been proved to be the key of the entire water splitting process, as the reaction kinetic limitation step.3 In this work, we developed a novel system with Co3O4 quantum dots(QDs) or Fe2O3 QDs as photosensitizer, a salophen cobalt(II) complex(Co SLP) as catalyst, and persulfate(S2-2O8) as the sacrificial electron acceptor(Fig. 1). The photocatalytic oxygen evolution rate of the systems were 75μmol/h/g and 84μmol/h/g over the cobalt(II) complex when Co3O4 QDs or Fe2O3 QDs was employed, respectively. While no O2 evolution were observed when either salophen cobalt(II) complex or QDs was absent. This high efficiency might be attributed to the interfacial hole transfer from photoexcited QDs to the cobalt(II) complex.

关键词： artificial photosynthesis oxygen production quantum dots cobalt catalyst

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Simulation of a Novel Single-column Cryogenic Air Separation Process Using LNG Cold Energy

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Physics Procedia 2015年 67卷 116-122页

作者： Zheng Jieyu Li Yanzhong Li Guangpeng Si Biao Institute of Refrigeration and Cryogenics Xi’an Jiaotong University Xi’an710049China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an710049China

In this paper, a novel single-column air separation process is proposed with the implementation of heat pump technique and introduction of LNG coldenergy. The proposed process is verifiedand optimized through simulation on the Aspen Hysys® platform. Simulation results reveal that thepower consumption per unit mass of liquid productis around 0.218 kWh/kg, and the total exergy efficiency of the systemis 0.575. According to the latest literatures, an energy saving of 39.1% is achieved compared with those using conventional double-column air separation *** introduction of LNG cold energy is an effective way to increase the system efficiency.

关键词： heat pump cryogenic air separation single-column process LNG cold energy recovery Aspen Hysys® simulation

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Thermal-hydraulic analysis and metal temperature computation for the water wall of a 1000MW ultra supercritical tower boiler with double reheat

Thermal-hydraulic analysis and metal temperature computation...

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International Conference on power engineering, ICOPE 2015

作者： Yang, Dong Wang, Long Bi, Yanshuang Xie, Beibei Wang, Gang Yao, Danhua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Xi'an Shaanxi710049 China Shanghai Boiler Works Ltd. No.250 Huaning Road Minhang District Shanghai200245 China

The ultra supercritical boiler technology with double reheat can significantly increase the efficiency of a Rankine cycle power plant, and reduce fuel consumption for a given output. Recently China is developing 1000MW ultra supercritical boiler with double reheat which is arranged in tower type and the steam parameters are 350bar, 605oC/613oC/613oC. Thermal-hydraulic analysis is the key factors for the design and operation of ultra supercritical boiler with double reheat. According to the boiler structure and furnace-sided heat flux, the water wall of an ultra supercritical tower boiler with double reheat is treated in this paper as a flow network system consisting of series-parallel loops, pressure grids and connecting tubes. Based on the mass, momentum and energy conservations and some supplementary equations, a mathematical model is developed. Pressure drop, mass flux distribution, outlet vapor temperatures and metal temperatures data in the water wall at BMCR (boiler maximum continuous rating), 75% THA (turbine heat acceptance) and 30% THA load are obtained by iteratively solving the mathematical model. The results show that the water wall in the ultra supercritical boiler can operate safely. © 2015 The Japan Society of Mechanical Engineers.

关键词： Pressure drop

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Experimental research on simultaneous removal of CO2, SO2 and NOx by amine-sulphone solution

Experimental research on simultaneous removal of CO2, SO2 an...

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International Conference on power engineering, ICOPE 2015

作者： Li, Lian Bin, Hu Li, Na Zhou, Qulan Zhang, Yi Shen, Jizhao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China North China Power Engineering Co. Ltd China Power Engineering Consulting Group Beijing100120 China Department of Housing and Circumjacent Property Management Xi'an Jiaotong University Xi'an710049 China Yangzhou Chenguang Special Equipment Co. Ltd. Yangzhou225800 China

Environmental problems caused by CO2, SO2, NOx and other pollutants have become increasingly prominent. It has been a research hotspot to remove CO2, SO2 and NOx simultaneously with simple technique, relative lo w operation cost. We made amine-sulphone solution with N-methyl-diethanolamine (MDEA) and dimethyl sulfoxide (DMSO) as the absorbent of SO2/CO2/NOx. A bubbling bed absorption system was designed and built to investigate the absorption properties of amine-sulphone solution toSO2/CO2/NOx. The solution formula and working condition were discussed to figure out the optimu m choices of formula, solution concentration and flo w rate of flue gas. According to the regulations of absorption rate, absorptive amount and removal ratio, the solution formula with 52.5%MDEA+17.5%DMSO showed the best simultaneous absorption properties to SO2/CO2/NOx. And 70% were the optimum concentration choice for the of amine-sulphone solution, taking absorbent cost, mass transfer and absorption quality into consideration. There's a flow rate inflexion point for the absorption of each gas, which is the boundary of rapid dropping and stable interval of removal ratio. The minimum of inflexion point for SO2/CO2/NOx was the optimu m flue gas flo w rate for high removal ratio and low cost, which was 1L/min in the experiment. © 2015 The Japan Society of Mechanical Engineers.

关键词： Carbon dioxide

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The selective catalytic reduction of NOx with CH4 on La1-xSrxMnO3 (x=0.2, 0.4) catalysts

The selective catalytic reduction of NOx with CH4 on La1-xSr...

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International Conference on power engineering, ICOPE 2015

作者： Zhang, Hang Li, Na Zhou, Qulan Lv, Chen Huang, Sijia Shen, Jizhao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Huazhong University of Science and Technology Wuhan430074 China Fujian Electric Power Survey and Design Institute Fuzhou350003 China Yangzhou Chenguang Special Equipment Co. Ltd. Yangzhou225800 China

Two kinds of typical perovskite catalysts La1-xSrxMnO3 (x=0.2, 0.4) as new catalysts for using in CH4-NO and CH4-N2O reaction is proposed, and the preparation method, characterization, catalytic activity of La1-xSrxMnO3 was investigated. The catalysts powder via sol-gel method was successfully synthesized in this paper. In addition, the catalytic activity of supported La1-xSrxMnO3 catalyst was tested in fixed bed reactor, and the effects O2 concentration on catalyst activity were explored at three different temperatures, 600°C, 700°C and 800°C. The catalytic reduction of NO and N2O by CH4 over La0.8Sr0.2MnO3 and La0.6Sr0.4MnO3 catalyst was performed separately. The conversion ratio of N2O was usually higher than that of NO when the temperature and other conditions were the same. With the decrease of temperature, the range of O2 concentration becomes narrower obviously on the NO conversion. However, the O2 content doesn't seem to have significant in fluence on the N2O conversion ratio. The La0.8Sr0.2MnO3 performed better on the reaction of CH4 and N2O when temperature increased, wh ile the La0.6Sr0.4MnO3 performed best on 700°C with a ratio of about 90%. © 2015 The Japan Society of Mechanical Engineers.

关键词： Perovskite

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Experimental study on CO2/SO2/NOx simultaneous absorption and separated desorption using compound amine sulphone solution

Experimental study on CO2/SO2/NOx simultaneous absorption an...

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International Conference on power engineering, ICOPE 2015

作者： Luo, Qinlan Li, Na Zhou, Qulan Zhang, Yi Shen, Jizhao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Housing and Circumjacent Property Management Xi'an Jiaotong University Xi'an710049 China Yangzhou Chenguang Special Equipment Co. Ltd. Yangzhou225800 China

To simplify devices and reduce the high energy consumption in removal processes of air pollutants in fossil fuel-fired power plants, the compound amine sulphone solutions of N-Methyldiethanolamine (MDEA) and dimethyl sulfoxide (DMSO) were explored for the simultaneous removal of CO2/SO2/NOX. The dynamic experiments of CO2/SO2/NOX simultaneous absorption and separated desorption were carried out to confirm the feasibility of the experimental system and evaluate the performance of the studied compound amine sulphone solution. The experimental results indicated that the simultaneous removal of CO2/SO2/NOX was feasible by the compound amine sulphone solution, the separate desorption of CO2 and NO was realized when the regeneration temperature was set at 50°C and 90°C, respectively. Especially, the solution of 2M MDEA +1M DMSO showed the highest absorption capacity and desorption capacity. © 2015 The Japan Society of Mechanical Engineers.

关键词： Desorption

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Optimization of Hydrogen Distribution Network Considering Pressure and heat recovery

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Energy Procedia 2015年 75卷 1147-1152页

作者： Ruifeng Dong Yunsong Yu Zaoxiao Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 PR China School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an 710049 PR China

Hydrogen is an important resource in chemical processes. In the hydrogen network, many units are operating at high temperature and pressure, which leads to a large energy change of hydrogen streams. However, the recovery of heat and work in the hydrogen flows has seldom been studied together with the optimization of hydrogen network. It is obviously that the reuse of heat and work energy will raise the effective utilization rate of energy. The recovery of heat could be realized by heat exchangers. The recovery of work will be realized by rotary work exchangers, which are composed of several compressors and turbines with the same shaft. A state space superstructure is adopted to handle all the variables. The mathematical model is built based on exergoeconomic analysis considering both energy and economic factors. The optimization problem will be a mixed integer nonlinear programming (MINLP) problem. The existing algorithms will be improved. A typical refinery hydrogen network is studied as an example. The state space superstructure, exergoeconomic analysis and proposed algorithm could solve the problem competently. The consideration of pressure and heat recovery could reduce the energy consumption and economic cost simultaneously.

关键词： Hydrogen network Heat recovery Work recovery Exergoeconomic analysis Global optimization algorithm

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A study of the effect of microstructure on liquid-solid impact

A study of the effect of microstructure on liquid-solid impa...

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International Conference on power engineering, ICOPE 2015

作者： Teng, Zhaohui Li, Na Zhou, Qulan Chen, Xi State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Department of Earth and Environmental Engineering Columbia University New YorkNY10027 United States International Center for Applied Mechanics SV Lab School of Aerospace Xi'an Jiaotong University Xi'an710049 China

Liquid drops hit against solid surface, which has an enormous influence on the mechanical properties of base solid surface during its service. Impact of the droplet makes the solid surface and some internal section of the base solid material generate high stress. The conical microstructure may decrease the dimensionless equivalent stress in solid. We investigated the effect of the microstructure with three different sizes by numerical simulation. In the paper, detail theoretic analyses of liquid-solid impact were carried out. Here the mathematics physics model was built to solve the liquid-solid impact problem The numerical method coupling liquid and solid region was designed and the impact procedure of spherical droplet to solid materials was simulated. We acquired the pressure distribution inside water drop and the transient equivalent stress field inside solid. High stress at the solid surface and some internal sections arose from impact of the droplet. The sections in solid with highest stress can be classified into the contact edge and the axis due to stress superposition. The stress in solid declined slightly at the condition with the microstructure (5μm high and a diameter of 1μm). The microstructure (50μm high and a diameter of 10μm) in this paper considerably decreased the average stress in solid. They may store liquid and yield a liquid film higher than the thickness of the microstructure, undertaking the droplet impact and acting as a cushion to the stress concentration in solid. These results may play a role in evaluating the base solid service properties based on the fundamental solution of liquid-solid impact and be valuable to understand the internal mechanism of liquid-solid impact, and are helpful to prevent the erosion of droplet to the solid materials. © 2015 The Japan Society of Mechanical Engineers.

关键词： Microstructure

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