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Investigation of exergy efficiency of organic Rankine cycle

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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Laser-induced Morphology Change and Photo-thermolysis of Gold Nano Particles with Application in Laser Dermatology

Laser-induced Morphology Change and Photo-thermolysis of Gol...

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2017第六届国际新材料大会

作者： Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University China

Based on the principle of selective photothermolysis,laser photothermal therapy is regarded as the most effective treatment methodology for port-wine stain（PWS）,which is a congenital vascular malformation caused by the expansion of capillaries in the dermis.1064 nm Nd:YAG laser has great potential for the treatment of deeper and larger ***,the clinical effectiveness is limited because of the weak absorption of blood to Nd:YAG *** order to enhance the blood absorption,spherical gold nanoparticles were prepared by Sodium citrate reduction method with average size of 16.7 nm and absorbance peak at 522 *** nanorods were prepared by Seeded growth method and modified by PEG with average length and width of 79.1 nm and 13.5 *** this aspect ratio of 5.89,a strong absorption band at050 nm in the near-infrared range is *** can inject spherical gold particles into the bloodstream to enhance the light absorption of blood in visible range,while using gold nanorod to increase absorbance of blood to Nd:YAG Laser for improving the cure rate of laser treatment of vascular *** absorption was increased by 1.25 times for 581 nm（PDL laser） and 3.71 times for 1064 nm（Nd:YAG laser）.To investigate the morphology change and photothermolysis of gold NRs induced by Nd:YAG laser and obtain the optimal irradiation conditions for effectively destroying the vascular lesions,tissue-like phantoms were prepared and exposed to Nd:YAG laser with various laser parameters to investigate the photothermolysis of gold *** obtained the optimal photothermolysis of gold NRs for destroying the blood vessel as follows:When the concentration of gold NRs is 26.67 g/mL,the Nd:YAG laser energy density should be 40 J/cm2,with long laser pulse width of 0.3 ms for ten pulses.

关键词： Laser-induced Morphology Change and Photo-thermolysis of Gold Nano Particles with Application in Laser Dermatology

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Numerical Investigation on the Performance of Different Primary Nozzle Structures in the Supersonic Ejector

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Energy Procedia 2017年 105卷 4997-5004页

作者： Kangkang Xue Kaihua Li Weixiong Chen Daotong Chong Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi’an JiaotongUniversity Xi’an Shaanxi 710049 P.R. China

Computational fluid dynamics (CFD) technique is employed to investigate the effect of primary nozzle structures on the supersonic ejector performance. The performance of the supersonic ejectors with three different nozzle structures, including conical nozzle, petalage nozzle and crenation nozzle, have been compared under the same conditions. Compared with the ejector equipped with the conical nozzle, the entrainment ratio of petalage nozzle is slightly smaller, while the critical back pressure increases by 5.2%. Just the opposite, the entrainment ratio of crenation nozzle is slightly higher, and the critical back pressure would decrease by 2.1%. In addition, the effects of primary/induced fluid pressure on the flow field (pressure and Mach number along the ejector centerline) are observed and analyzed to explain the mixing process occurring inside the ejector. It finds out that the shape of the mixing layer in the supersonic ejector with different nozzles is different.

关键词： Supersonic ejector CFD Primary nozzle Entrainment ratio Critical back pressure

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Numerical simulation of flow characteristics for a labyrinth passage in a pressure valve

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Journal of Hydrodynamics 2016年第4期28卷 629-636页

作者：王海民赵越汪建兴孔祥帅刘欢李科良王喜芳 School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology

A tortuous labyrinth passage consists of a series of right angle turns in a disk of high pressure control *** this paper,numerical simulations are made for the velocity and pressure distributions in this *** is shown that the “series passage” can induce a pressure dropping more *** main function of the “series passage” is to induce a pressure dropping while the “parallel passage” is mainly to regulate the *** a cross sectional area process,a series of reduction and expansion,the pressure will also see dropping and partial recovery,which is called the multistage pressure *** this way,the velocity can be controlled in a reasonable level anywhere in this tortuous labyrinth *** the fluid pressure dropping in a downwards serrated way,the pressure is higher than the local saturate vapor pressure,therefore,no cavitation is induced by the phase transition.

关键词： passage valve dropping multistage turns sectional anywhere regulate vortex inlet

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Experimental study on heat transfer to supercritical CO2 flowing in vertical upward tube at medium mass flux

Experimental study on heat transfer to supercritical CO2 flo...

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ASME 2017 Nuclear Forum, NUCLRF 2017, collocated with the ASME 2017 power Conference Joint with ICOPE 2017, the ASME 2017 11th International Conference on Energy Sustainability, and the ASME 2017 15th International Conference on Fuel Cell Science, engineering and Technology

作者： Zhang, Qian Li, Huixiong Kong, Xiangfei Zhang, Jun Lei, Xianliang Zhang, Weiqiang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'anShaanxi China North Carolina State University United States Burlington Laboratory 3144 North Carolina State University RaleighNC27607 United States

ISBN: (纸本)9780791840597

An experimental study was performed on heat transfer characteristics of supercritical pressure CO2 (SC-CO2) flowing at medium mass flux conditions in a vertically-upward tube of 16 mm inner diameter at the Heat Transfer and flow test loop of Supercritical CO2 (HTF-SCO2) in Xi’an Jiaotong University. Experimental parameters included the pressure ranging from 7.5 to10.5 MPa, the mass flux of 400-600 kg/m2s, and the heat flux of 20-100 kW/m2. Based on the experimental data, effects of mass flux, heat flux and operation pressure on heat transfer characteristics of SC-CO2 were thoroughly discussed. With the decrease of mass flux and increase of heat flux, heat transfer characteristics of SC-CO2 becomes worse and worse. The wall temperature rises to high levels with the occurrence of a wall temperature peak and the wall temperature peak also rises remarkably with the decrease in mass flux and increase in heat flux. Especially, effect of pressures on the heat transfer of SC-CO2 was found to be quite different from that previously reported in literature. When the heat flux is low (such as 30 kW/m2), the HTD was diminished with the increase in pressures, but when the heat flux is up to 50 kW/m2, the HTD is surprisingly intensified by the increase of pressure. The buoyancy effect was considered to explain this distinct influence of pressure on the heat transfer of SC-CO2 by employed a non-dimensional parameter Bu. With the increase of pressure, buoyancy effect was diminished owing to the decrease of density difference between fluids near the wall and the center. When heat flux was lower, the Bu was located between 5×10-6 and 10-4, where buoyancy effect impaired heat transfer, so the heat transfer coefficient increased by rising pressure. But when heat flux was larger, the Bu was above 10-4, where buoyancy effect began to enhance heat transfer, as a result, the heat transfer coefficient was reduced by weakened buoyancy effect because of the increase of pressure (CSPE). Copyrig

关键词： Heat flux

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Ferrites boosting photocatalytic hydrogen evolution over graphitic carbon nitride: a case study of(Co, Ni)Fe_2O_4 modification

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Science Bulletin 2016年第4期61卷 292-301页

作者： Jie Chen Daming Zhao Zhidan Diao Miao Wang Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

The charge cartier separation and surface catalytic redox reactions are of primary importance as elementary steps in photocatalytic hydrogen evolution. In this study, both of these two processes in photocatalytic hydrogen evolution over graphitic carbon nitride （g-C3N4） were greatly promoted with the earth-abundant ferrites （Co, Ni）Fe2O4 modification. CoFe2O4 was further demonstrated to be a better modifier for g-C3N4 as compared to NiFe2O4, due to the more efficient charge carrier transfer as well as superior surface oxidative catalytic activity. When together loading CoFe2O4 and reductive hydrogen production electrocatalyst Pt onto g-C3N4, the obtained Pt/g-C3N4/CoFe2O4 photocatalyst achieved visible-light （2 〉 420 nm） hydrogen production rate 3.5 times as high as Pt/g-C3N4, with the apparent quantum yield reaching 3.35 % at 420 nm.

关键词： Graphitic carbon nitride FerritesPhotocatalytic water splitting Solar hydrogenconversion

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Spontaneous photoelectric field-enhancement effect prompts the low cost hierarchical growth of highly ordered heteronanostructures for solar water splitting

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Nano Research 2016年第6期9卷 1561-1569页

作者： Yankuan Wei Jinzhan Su XiaokangWan Liejin Guo Lionel Vayssieres International Research Center for Renewable Energy State Key Laboratory for Multiphase Flow in Power Engineering School of Energy &Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this study, a potentially universal new strategy is reported for the large-scale, low-cost fabrication of visible-light-active highly ordered heteronanostructures based on the spontaneous photoelectric-field-enhancement effect inherent in pyramidal morphology. The hierarchical vertically oriented arrayed structures comprise an active molecular co-catalyst at the apex of a visible-light-active large band gap semiconductor for low-cost solar water splitting in a neutral aqueous medium without the use of a sacrificial agent.

关键词： bismuth vanadate co-catalysts photocatalysis solar water splitting oxygen evolution

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

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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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Prediction on bubble departure diameter of high pressure boiling water in vertical upward smooth tubes 17

Prediction on bubble departure diameter of high pressure boi...

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

作者： Guo, Kaikai Li, Huixiong Zhang, Qing Kong, Xiangfei Luo, Qing Xue, Yuqing State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'an Shaanxi China China Huaneng Clean Energy Research Institute Beijing102209 China Xi’an Thermal Power Research Institute Co. Ltd Xi'an Shaanxi China

As one of the most important parameters of boiling phenomena, the bubble departure diameter has great influence on the vapor-liquid interfacial heat transfer and the convection heat transfer between the wall and the fluid involved. At present, the RPI wall boiling model has been often used to simulate the boiling phenomenon, however, due to the fact that the existing bubble departure diameter models embedded in the RPI wall boiling model were mostly derived from fitting of limited experimental data, there exists great limitation to the applicability of the RPI wall boiling model. Moreover, the experimental data of the bubble departure diameter was mostly obtained at low and middle pressures, and no experimental data of the bubble departure diameter was measured at high pressure (more than 10 MPa). So the effectiveness of the RPI wall boiling model at high pressures should be studied further. A series experimental investigations on the heat transfer of high pressure boiling water in vertical upward tubes has been conducted at the Hi-TaP-XJTU test loop, and wall temperatures of vertical upward tubes were acquired at pressures ranging from 1 to 19 MPa. In combinations with the experimental studies, numerical simulations were performed on the heat transfer of high pressure boiling water flow in vertical upward tubes by using the RPI wall boiling model under conditions corresponding to the experimental investigation. Then,, the reference diameter (dref) used in the Tolubinsky bubble departure diameter model was modified and selected for a specific water pressure so as to make the numerically-obtained wall temperature to satisfactorily match the corresponding experimentally-measured wall temperature at the specific pressure. It was found that the value of dref was closely related to the pressures of the boiling water, but was independent of the mass flux of the water and the heat flux on the wall at a specific pressure. Based on a correlation between the water pressures a

关键词： Heat flux

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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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