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Optimization of cold-end system of thermal power plants based on entropy generation minimization

Frontiers in Energy 2022年第6期16卷 956-972页

作者： Yue FU Yongliang ZHAO Ming LIU Jinshi WANG Junjie YAN State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Cold-end systems are heat sinks of thermal power cycles,which have an essential effect on the overall performance of thermal power *** enhance the efficiency of thermal power plants,multi-pressure condensers have been applied in some large-capacity thermal power ***,little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be ***,the design optimization methods of coldend systems with single-and multi-pressure condensers are developed based on the entropy generation rate,and the genetic algorithm(GA)is used to optimize multiple *** parameters,including heat transfer area of multi-pressure condensers,steam distribution in condensers,and cooling water mass flow rate,are optimized while considering detailed entropy generation rate of the cold-end *** results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is ***,the economic performance can be improved with the adoption of the multi-pressure cold-end *** compared with the single-pressure cold-end system,the excess revenues gained by using dual-and quadruplepressure cold-end systems are 575 and 580 k$/a,respectively.

关键词： cold-end system entropy generation minimization optimization economic analysis genetic algorithm(GA)

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Rapid modeling of transient processes in hydrogen-blended natural gas pipelines featuring injection and withdrawal points

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International Journal of Hydrogen Energy 2025年

作者： Gong, Junhua Zhou, Chaoqun Wang, Yanxin Deng, Yajun Chen, Yujie Wang, Peng Yu, Bo Chen, Bin Yu, Zhipeng Wang, Bohong School of Mechanical Engineering Beijing Institute of Petrochemical Technology Beijing102617 China Changqing Oil and Gas Transportation Branch of Northwest Company of PipeChina Xingqing District Ningxia Yinchuan City750004 China PipeChina Engineering Technology Innovation Co.Ltd Tianjin300450 China School of Petroleum Engineering Yangtze University Wuhan430100 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China National & Local Joint Engineering Research Center of Harbor Oil & Gas Storage and Transportation Technology/Zhejiang Key Laboratory of Pollution Control for Port-Petrochemical Industry Zhejiang Ocean University Zhoushan316022 China

Blending hydrogen into natural gas pipelines enables the large-scale delivery and application of hydrogen, contributing to carbon emission reduction and promoting the transition to cleaner energy sources. Accurate and efficient predictions of transient processes in such pipelines are critical for effective management and operation. This study proposes a Fourier Neural Operator (FNO)-based model for the rapid prediction of transient processes in hydrogen-blended pipelines with injection and withdrawal points. The model is trained using numerical simulation data of pressure and flow dynamics, with initial conditions, boundary conditions, and the hydrogen blending ratio as inputs to predict hydraulic parameters along the pipeline over time. By optimizing data preprocessing and neural network hyperparameters, the model achieves high accuracy and efficiency in predicting hydraulic states. The FNO model achieves average Root Mean Squared Errors (RMSEs) of 1.06 × 10−3, 1.64 × 10−3, and 7.40 × 10−4 for pressure, flow rate, and density, respectively, with the Coefficient of Determination (R2) exceeding 0.99 for all three variables. Furthermore, the model demonstrates strong generalization capabilities, accurately predicting hydraulic states for pipeline topologies and scenarios beyond the training data. In these cases, the RMSE remains in the order of 10−3 or smaller. For a 100 km pipeline, the computational efficiency of the FNO model is at least 969 times higher than that of traditional numerical methods, with the maximum efficiency improvement reaching 5168 times as the number of pipeline cases simultaneously predicted increases. These results highlight the potential of the FNO model for real-time applications in hydrogen-blended natural gas pipeline management. © 2025 Hydrogen Energy Publications LLC

关键词： Mean square error

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Large Eddy Simulation Study on the Turbulence and Flame Characteristics under Analogical Integral Scale and Turbulence Intensity of Turbulent Premixed Flames

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Journal of Thermal Science 2023年第1期32卷 488-501页

作者： WEI Xutao WANG Jinhua ZHANG Meng HUANG Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Bunsen burner is a typical geometry for investigating the turbulence-flame *** most experimental studies,only turbulence intensity u′and integral scale l0 are used to characterize the turbulent flow field,regardless of the perforation geometry of perforated ***,since the geometry influences the developing process and vortex broken,the plate geometry has to be considered when discussing the flame-turbulence *** order to investigate conditions at the same l0 and u′using different geometries,large eddy simulation of CH_(4)/air flames with dynamic TF combustion model was *** model validation shows good agreement between Large Eddy Simulation(LES)and experimental *** the non-reacting flows,the Vortex Stretching of circular-perforated plate condition is always larger than that of slot-perforated plate condition,which comes from the stresses in the flow fields to stretch the vorticity *** reacting flows,at the root of the flame,the Vortex Stretching plays a major role,and the total vorticity here of circular-perforated plate condition is still larger(53.8%and 300%larger than that of the slot-perforated plate at x/D=0 and x/D=2.5,respectively).More small-scale vortex in circular-perforated plate condition can affect and wrinkle the flame front to increase the Probability Density Function(PDF)at large *** 3D curvature distributions of both cases bias to negative *** negative trend of curvatures at the instant flame front results from the Dilatation ***,the value of the Vortex Stretching and the Dilatation at the flame front of circular-perforated plate condition is obviously larger.

关键词： large eddy simulation integral scale turbulence intensity vorticity flame curvature

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Assisting effect of Al_(2)O_(3) on MnO_(x) for NO catalytic oxidation

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Green Energy & Environment 2021年第6期6卷 903-909页

作者： Denghui Wang Hui Li Qi Yao Shien Hui Yanqing Niu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an710049China

Various Mn-based catalysts for NO oxidation were prepared using MnO_(x)as active compound,while Ti O_(2)and Al_(2)O_(3)were adopted as catalyst *** performance of the catalysts was tested to study the effect of support on Mn-based catalyst *** of the catalysts followed as Mn_(0.4)/Al>Mn_(0.2)/Al>Mn_(0.4)/Ti>Mn_(0.2)/Ti>MnO_(x)>Al_(2)O_(3)on the whole,indicating the synergism of MnO_(x)and Al_(2)O_(3)for NO catalytic *** were analyzed according to characterization *** oxygen on catalyst rather than lattice oxygen was detected as the active oxidizer for NO *** catalyst support,Al_(2)O_(3)provided more sites to carry surface adsorbed oxygen than TiO_(2),resulting in the presence of more active oxygen on Mn O_(x)/Al_(2)O_(3)than on MnO_(x)/TiO_(2).Moreover,MnO_(x)/Al_(2)O_(3)possessed high surface area and pore volume,which greatly benefited the adsorption of NO on catalyst and further favored the oxidation of NO by active *** these advantages helped Mn_(0.4)/Al exhibited the best catalytic efficiency.

关键词： NO catalytic oxidation MnO_(x)/Al_(2)O_(3) NO_(2) Active oxygen

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Quantitative Evaluation of Clinical Efficacy of Laser Thermotherapy for Port-Wine Stains Through Reflectance Spectra Measurements and an Inverse Radiation Algorithm

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Zhongguo Jiguang/Chinese Journal of Lasers 2025年第9期52卷

作者： Li, Dong Li, Xiaoyang Zhang, Pengfei Chen, Bin Ying, Zhaoxia State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Shaanxi Provincial Institute for Skin Disease and STD Control Shaanxi Xi’an710003 China

Objective Port-wine stains (PWS) are congenital vascular malformations caused by the abnormal dilation of capillaries and venules in the skin. Affecting 0.3%‒0.5% of newborns, PWS typically manifest as pinkish patches on the face and neck that darken and thicken over time, significantly impacting patients’physical and mental well-being. Pulsed dye laser (PDL) therapy, based on selective photothermolysis, is the gold standard for PWS treatment. By targeting hemoglobin in abnormal blood vessels with specific wavelengths, PDL induces thermal damage to the vasculature while sparing surrounding tissues. However, due to variability in skin types, lesion depths, and laser parameters, clinical outcomes often depend on subjective evaluations and physician experience. These limitations underscore the urgent need for objective, quantitative, and noninvasive methods to assess skin structure and monitor treatment efficacy. This study integrates reflectance spectroscopy with an inverse Monte Carlo radiation method to quantify changes in key skin parameters before and after laser treatment. By measuring and reconstructing parameters such as epidermal thickness, melanin volume fraction, blood volume fraction, and blood oxygen saturation, this study establishes a robust framework for evaluating treatment outcomes and optimizing laser parameters. Additionally, it investigates differences in treatment responses between pediatric and adult patients, providing critical insights for personalized therapeutic strategies. Methods Eleven patients with PWS underwent pulsed dye laser (PDL) therapy at a wavelength of 595 nm, with an energy density of 8 J/cm2 and a fixed spot diameter of 7 mm. Reflectance spectra of the skin were measured before and after treatment using an HR400 CG-UV-NIR spectrometer (Fig. 1). To enhance efficacy, a double-irradiation strategy was employed, in which the second laser exposure followed the first after five minutes. For spectral analysis, an inverse Monte Carlo r

关键词： Hemoglobin oxygen saturation

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Predicting Self-Diffusion Coefficients of Light Gases in Supercritical Carbon Dioxide: A Molecular Dynamics Method

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The Journal of Supercritical Fluids 2025年

作者： Tongjia Zhang Bowei Zhang Jie Zhang Xiaoran Rong Hui Jin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 PR China

The methanation of CO 2 and supercritical CO 2 (scCO 2 ) fracturing represent effective approaches for CO 2 utilization and greenhouse effect mitigation. In these process, light gases like H 2 , O 2 , CO, CH 4 are commonly involved. However, limited studies have focused on the diffusion behavior of these gases in scCO 2 under high-pressure conditions, as well as a shortage of self-diffusion coefficient data and prediction equations specifically designed for scCO 2 solvents. To address this gap, molecular dynamics (MD) simulations were employed to compute the self-diffusion coefficients of several light gases in scCO 2 across a wide temperature range (313 K–713 K) and at high pressures (75.994 bar, 101.325 bar and 126.656 bar) under infinitely dilute conditions. The effects of temperature, density, viscosity, molecular mass, and solute–solvent interaction energy on the self-diffusion behavior were systematically analyzed. Two empirical equations (a Speedy–Angell-type power-law equation and a newly developed equation incorporating temperature, density, and viscosity) were refitted based on simulation data. The overall relative errors are 4.52% and 4.44%, respectively, indicating an improved accuracy compared to conventional experimental and MD-based empirical equations.

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Characterizations of gas-liquid interface distribution and slug evolution in a vertical pipe

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Petroleum Science 2023年第5期20卷 3157-3171页

作者： Hai-Yang Yu Qiang Xu Ye-Qi Cao Bo Huang Han-Xuan Wang Lie-Jin Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi’an710049ShaanxiChina

Large vertical pipes are key structures connecting subsea wells to offshore ***,existing studies mainly focus on small vertical *** a vertical acrylic pipe with 80 mm inner diameter and 11 m height,a high-speed camera was used to visually research the influences of pipe diameters,liquid properties and inlet effect on air-water co-flow *** flow regime maps of vertical pipes(diameters are in the range of 50e189 mm)were compared and the critical gas velocity of the transition boundary from bubble to slug flow tended to increase with the increase of diameters at D≥80 ***-flux models were established in different flow regimes and liquid properties have a significant effect on drift coefficients of bubble flow and slug flow(void fraction a≤0.4).The influence of inlet turbulent effect on the gas-liquid interface distribution gradually weakened and disappeared from the pipe base to 85D,where the flow was fully *** frequency has a trend of increase first and then decrease with the gas Weber numbers increasing at low liquid superficial velocities(J_(L)≤0.31 m/s).And on the basis of this law,a new slug frequency correlation was *** was found that there was an exponential relationship between the ratio of lengths of Taylor bubble to slug and the void fraction.

关键词： Void fraction flow regime Drift coefficien Slug frequency Taylor bubble length

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Numerical simulation of bubble behavior in a quasi-2D fluidized bed using a bubble-based EMMS model

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Particuology 2019年第5期17卷 40-54页

作者： Hao Wang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'an 710049 Shaanxi China

Bubbles formed during chemical processes in fluidized beds govern the bed hydrodynamics and opera-tional efficiency, thereby having a significant impact on their design and scale-up. In this study, a two-fluid model was used to simulate the bubble behavior in a quasi-two-dimensional fluidized bed within the bubble-based energy minimization multiscale (EMMS) approach. We performed experiments to verify the model and proposed a correlation of the heterogeneous index for various parameters to calculate the coefficient of drag for the bubble-based EMMS model. Moreover, the simulation results obtained from the homogeneous drag models and EMMS bubbling model were compared with experimental data and empirical correlations. The simulation results of the EMMS approach showed good agreement with the experimental data in the distribution of the vertical bubble velocity with chord length. Compared with the results from the homogeneous models, the distributions of vertical velocity and diameter of the bubbles predicted by the EMMS-bubbling model were in better agreement with empirical correlations. Moreover, the frequency distributions of bubble properties including bubble diameter, aspect ratio, and shape factor for different gas-inlet velocities were obtained.

关键词： Energy minimization multi-scale approach Heterogeneous index Fluidized bed Bubble

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Cyclone separation in a supercritical water circulating fluidized bed reactor for coallbiomass gasification： Structural design and numerical analysis

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Particuology 2018年第4期16卷 55-67页

作者： Guoxing Li Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

A new concept of a supercritical water （SCW） circulating fiuidized bed reactor is proposed to produce hydrogen from coal/biomass gasification. The cyclone is a key component of the reactor system, in this paper, cyclones with a single circular inlet （SCI） or a double circular inlet （DCI） were designed to adapt to the supercritical conditions. We evaluated the separation performance of the two cyclones using numerical simulations. A three-dimensional Reynolds stress model was used to simulate the turbulent flow of the fluid, and a stochastic Lagrangian model was used to simulate the particle motion. The flow fields of both cyclones were three-dimensionally unsteady and similar to those of traditional gas-solid cyclones. Secondary circulation phenomena were discovered and their influence on particle separation was estimated. Analyzing the distribution of the turbulence kinetic energy revealed that the most intensive turbulence existed in the zone near the vortex finder while the flow in the central part was relatively stable. The particle concentration distribution was non-uniform because of centrifugal forces. The distribution area can be divided into three parts according to the motion of the particles. In addition, the separation efficiency of both cyclones increased with the inlet SCaN velocity. Because of its perturbance flow, the DCI separator had higher separation efficiency than the SCI separator under comparable simulations. However, this was at the expense of a higher pressure drop across the cyclone.

关键词： CycloneStructural design Supercritical water-solid flow Separation performance Circulating fluidized bed Computational fluid dynamics

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Investigation on a Supercritical Water Gasification System with CO_(2)as Transporting Medium

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Journal of Thermal Science 2023年第4期32卷 1614-1625页

作者： WANG Weizuo LU Bingru SHI Jinwen ZHAO Qiuyang JIN Hui State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF) Xi’an Jiaotong UniversityXi’an710049China

As a benign energy vector,hydrogen has been discussed for a long *** water gasification was one of good ways to produce ***,supercritical water gasification system with H_(2)O transporting was energy consuming in the process of heating due to the high specific heat of H_(2)O.A new supercritical water gasification system was established in this paper with supercritical CO_(2)as medium *** plastics were used as the sample transported by CO_(2).Production yields,energy flow and exergy flow of the system were collected and the influence of temperature,pressure,gasification concentration and transporting concentration was *** flow of H_(2)O input into the reactor was 1000 kg/*** typical condition was as follow:temperature 923.15 K,pressure 23 MPa,and the mass ratio of water,sample and transporting medium was 100:9:*** of H_(2),CH4,CO and CO_(2)at this condition was 8.1 kg/h,39.6 kg/h,6.6 kg/h and 137.5 kg/h,*** system with H_(2)O transporting was used to compare with the supercritical CO_(2)transporting system and proved that system with CO_(2)transporting could reduce the loss of both energy and exergy while the reduce of each gas production yield was less than 0.1 mol/mol.

关键词： phenolic plastics supercritical water gasification CO_(2)-transporting system energy and exergy flow

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