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Thermodynamic Optimization of a Double-pressure Organic Rankine Cycle Driven by Geothermal Heat Source

Energy Procedia 2017年 129卷 591-598页

作者： Qingxuan Sun Yaxiong Wang Ziyang Cheng Jiangfeng Wang Pan Zhao Yiping Dai Institute of Turbomachinery State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 People’s Republic of China

Geothermal energy, as a typical low-temperature heat source, has been exploited for decades to generate electricity. Organic Rankine cycle (ORC) system has a high energy conversion efficiency due to the good performance of organic fluids under the geothermal water temperature. In this study, a double-pressure organic Rankine cycle system driven by geothermal heat source is used to generate electricity. The double-pressure ORC system achieves the cascaded utilization of energy, which can improve the efficiency of energy conversion. Mathematical model is established based on thermodynamic laws, and the overall system performance has been evaluated. A parametric analysis is conducted to examine the effects of some key thermodynamic parameters, namely turbine high-level inlet pressure, turbine low-level inlet pressure, turbine high-level inlet temperature, on the system performance. Parametric optimization is conducted by means of genetic algorithm (GA) to find the maximum system performance. At the same time, the performances of three organic working fluids are examined. Results indicate that R245fa has a better performance among the three organic fluids. The exergy efficiency of overall system exceeds 5.8% under the supply water of 120℃, and it produce more than 800kW electricity with the geothermal water at the mass flow rate of 250t/h. It is also found that the exergy efficiency has peak value under the effect of turbine high-level inlet pressure and turbine low-level inlet pressure. In addition, increasing turbine high-level inlet temperature brings a positive effect to the system performance. Exergy analysis is also conducted and the result shows that the main exergy loss occurs in high-pressure evaporator. By system optimization, the double-pressure organic Rankine cycle has a better performance in utilizing geothermal energy than single-pressure system.

关键词： Geothermal Organic Rankine cycle Double-pressure

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Lithium–Sulfur Batteries: Flexible and High‐Loading Lithium–Sulfur Batteries Enabled by Integrated Three‐In‐One Fibrous Membranes (Adv. Energy Mater. 38/2019)

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Advanced Energy Materials 2019年第38期9卷

作者： Jianan Wang Guorui Yang Jie Chen Yunpeng Liu Yuankun Wang Cheng‐Yen Lao Kai Xi Duowen Yang Christopher J. Harris Wei Yan Shujiang Ding Ramachandran Vasant Kumar Department of Applied Chemistry School of Science MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter State Key Laboratory for Electrical Insulation and Power Equipment Xi'an Jiaotong University Xi'an 710049 China Department of Environmental Science and Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Materials Science and Metallurgy University of Cambridge Cambridge CB3 0FS UK

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Multi-objective optimization of a printed circuit heat exchanger design 17

Multi-objective optimization of a printed circuit heat excha...

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17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017

作者： Wang, L. Chen, M. Shi, S. Che, D. Sun, X. Department of Nuclear Engineering and Radiological Sciences University of Michigan 2355 Bonisteel Blvd. Ann ArborMI48109-2104 United States State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi710049 China

Due to their high effectiveness and compact size, printed circuit heat exchangers (PCHEs) appear promising to be employed as intermediate heat exchangers (IHXs) in High-Temperature Gas-cooled Reactors (HTGRs). In the literature, PCHEs of zigzag mini-channel designs have demonstrated superior performance in heat transfer and pressure drop. In this research, a three-dimensional numerical simulation was performed for a PCHE using computational fluid dynamics (CFD) tool ANSYS FLUENT to study the effects of the zigzag pitch and angle, and channel diameter on its thermal-hydraulic performance. The mass, momentum, and energy equations were solved using a finite volume method by considering steady-state, incompressible laminar flow. The FLUENT numerical model was validated by comparing the simulation results with the experimental data obtained in a high-temperature helium test facility. The comparison showed overall good agreement between the simulations and experiments. In addition, it was challenging to obtain accurate correlations/models for the Nusselt number and friction factor with various geometrical and operational parameters considered. In our study, two artificial neural network (ANN) models were applied by utilizing the CFD results to predict the Nusselt number and friction factor in PCHE zigzag channels with different geometrical configurations and operational parameters. Consequently, the computation time needed for the PCHE design optimization process could be significantly reduced. The comparison between the ANN predictions and CFD results showed that the ANN models could predict the numerical data with good accuracies. Furthermore, to achieve an optimal heat exchanger design, two conflicting evaluation criteria were proposed based on the capital and operational costs. Finally, the Non-dominated Sorting Genetic Algorithms (NSGA-II) and the proposed ANN models were combined and utilized to optimize the geometrical design parameters of the zigzag-channel PCHEs.

关键词： Multiobjective optimization

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Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor

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Particuology 2016年第4期14卷 95-101页

作者： Xuedong Jiang Ning Yang Bolun Yang Department of Chemical Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Center for Mesoscience and State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China

Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.

关键词： Computational fluid dynamics External loop airlift reactor Drag model Gas holdup Mnltiscale Mesoscale

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Gas and Liquid flow Rate Measurement in Wet Gas Based on Differential Pressure Signals

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Jixie Gongcheng Xuebao/Journal of Mechanical engineering 2017年第24期53卷 55-62页

作者： Bai, Bofeng Zheng, Xuebo Qiu, Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Scientific Information Division Xinjiang Oilfield Company Karamay834000 China

The basic characteristics of differential pressure signals and the limitation of flow rate metering methods based on differential pressure are studied analytically and experimentally. Through the investigation into differential pressure signals of orifice plate and V-cone, it is found that the two-phase differential pressure is mainly caused by gas phase and is slightly affected by the liquid phase. In the case of low liquid hold up, the frictional pressure drop can be decreased due to the presence of the thin liquid film on the wall, resulting in that the two-phase differential pressure, pressure loss and pressure loss ratio decrease at first and then increase as the liquid hold up increases. The fluctuation of the differential pressure is stochastic, causing the fluctuation characteristic parameters, such as the standard deviation, having the properties of poor stability and repeatability. This makes it difficult to be applied to industrial wet gas metering. The error propagation analysis demonstrates that the prediction error of liquid phase flow rate is much larger than that of the gas phase, which is a universal phenomenon of metering methods based on over-reading correlations. Finally, we recommend that for wet gas with high gas void fraction, the liquid flow rate should be measured independently. The non-monotonicity of the pressure loss ratio needs to be concerned if it is chosen as the characteristic parameter. Parameters with poor repeatability, such as standard deviation, are not recommended for wet gas metering. © 2017 Journal of Mechanical engineering.

关键词： flow rate

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Correlations of Coal Chemical Properties in China: Quantitative Analysis from Thousands of Data

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Energy Procedia 2017年 105卷 1339-1343页

作者： Chang’an Wang Song Wu Wufeng Chen Qiang Lv Defu Che State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University No 28 Xianning West Road Xi’an 710049 China

Coal chemical properties show conspicuous impacts on its reactivity and thermal conversion. Nevertheless, the quantitative analysis of coal property indice in China is insufficient. Here, we quantitatively analyzed the correlations of various chemical properties of coals from thousands of data. Noteworthy variations were captured with some quantified expressions between coal properties obtained.

关键词： coal property quantitative analysis fuel ratio coal rank energy conversion fossil fuel

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An overview of photocatalytic materials

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Journal of Materiomics 2017年第1期3卷 1-2页

作者： Shaohua Shen Coleman Kronawitter George Kiriakidis International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityShaanxi 710049China Department of Chemical Engineering University of CaliforniaDavisDavisCA 95616USA Institute of Electronic Structure and Laser Foundation for Research and Technology HellasP.O.Box 152771110 HeraklionGreece

Photocatalysis is an emerging technology that enables a wide variety of applications,including degradation of organics and dyes,antibacterial action,and fuel generation through water splitting and carbon dioxide *** inorganic semiconducting materials have been explored as photocatalysts,and the versatility of these materials and reactions has been expanded in recent *** the relationship between the physicochemical properties of photocatalytic materials and their performances as well as the fundamentals in catalytic processes is important to design and synthesis of photocatalytic materials.

关键词： materials. reduction. photocatalytic

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Investigation of exergy efficiency of organic Rankine cycle

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IOP Conference Series. Earth and Environmental Science 2019年第1期354卷 012050-012050页

作者： Liu, G L Xu, J L Cao, S Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing 102206 Beijing China School of Energy and Power Engineering Zhengzhou University of Light Industry Zhengzhou 450002 Henan Province China

Organic Rankine cycle (ORC) which recovers waste heat in the temperature range of 80°C-140°C was investigated. Exergy efficiencies of various components and ORC system were paid great attention. The working fluids of R245fa and R600a are used. It is found that, for saturated ORCs, the expander inlet temperature has the optimum value, so the system exergy efficiency is maximum. With the increase of heat source temperature, the optimal inlet temperature of the expander is also increased. And also for saturated ORCs, the exergy efficiencies of evaporator and expander are highest efficiency, when evaporator exergy efficiency is increased with increase of heat source temperatures, the expander exergy efficiency is unchanged. The condenser decreased exergy efficiencies by increasing the heat source temperatures.

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Effects of Coal Blending and Operating Conditions on Combustion and NO x Emission Characteristics in a Tangentially-fired Utility Boiler

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Energy Procedia 2017年 105卷 4015-4020页

作者： Debo Li Qiang Lv Yongxin Feng Chang’an Wang Xuan Liu Kai Chen Kai Xu Jun Zhong Defu Che Electric Power Research Institute of Guangdong Power Grid Corporation Guangzhou 510080 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The influences of operating conditions, such as excess air ratio and SOFA arrangement, on temperature distributions, species distributions, NO x emissions and burnout of a tangentially-fired utility boiler using bituminous and blended coal were investigated by numerical approach in the present study. The simulation results show that the fuel type exhibits certain effect on the temperature distributions and the NO x emissions. Moreover, higher excess air ratio could restrain the CO formation but promote NO x emission. The temperature and the species distributions are highly related to the SOFA arrangement. In addition, SOFA technology is still an effective approach to control the NO x emissions during blended coal combustion, while the disadvantageous effect on char burnout should be considered.

关键词： coal blending combustion NOx emission numerical simulation utility boiler

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Numerical Study on Combustion and Heat Transfer Properties Under Oxy-fuel Condition in a 600MW Utility Boiler

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Energy Procedia 2017年 105卷 4009-4014页

作者： Debo Li Xuan Liu Chang’an Wang Kai Xu Qiongliang Zha Qiang Lv Yongxin Feng Jun Zhong Defu Che Electric Power Research Institute of Guangdong Power Grid Corporation Guangzhou 510080 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China

Oxy-fuel combustion is recognized as one of the most promising CO 2 capture technologies. Under oxy-fuel combustion, the concentrations of CO 2 and H 2 O are much higher, result in different temperature profiles and heat transfer properties. In this study, a modified computational fluid dynamics (CFD) model-was developed for a 600 MW tangentially-fired boiler. Different oxygen volume fractions and two flue gas recycle modes (dry recycle and wet recycle) were numerically investigated, focusing on the properties of combustion and heat transfer. The results indicate the peak temperature in the burner zone decreases in oxy-fuel combustion, because of the high heat capacity and chemical reactivity of CO 2 . Compared with air-fired combustion, similar total heat transfer rate in furnace can be achieved at 27.0% and 28.3% of oxygen volume fraction for wet and dry recycle. These findings indicate retrofitting an existing boiler with oxy-fuel combustion technology is entirely feasible.

关键词： oxy-fuel combustion WSGGM numerical simulation combustion properties heat transfer properties

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